Gastrointestinal problems in cats

Possible diseases, the importance of the gut microbiome and the use of probiotics.

Gastrointestinal Diseases in Cats: Causes, Symptoms and Treatment

Gastrointestinal problems in cats are among the most common health disorders in cats and range from acute vomiting or diarrhea to chronic digestive issues. They can lead to dehydration, nutrient deficiencies or weight loss. Sudden vomiting, diarrhea, and appetite disorders are common reasons for a visit to the vet.

Symptoms such as vomiting, diarrhea, flatulence, or loss of appetite can indicate a variety of possible causes – from harmless feed intolerances to severe diseases such as gastroenteritis, pancreatitis, or chronic bowel disease (IBD). In this article, you will learn which digestive disorders can occur in cats, how to recognize gastrointestinal problems, and when a visit to the vet is necessary.

Stomach problems with vomiting affect about 10% of all cats annually. Causes can be hairballs, feed intolerances, infections, or serious conditions such as liver or pancreatic problems. Approximately 5–10% of all cats occasionally suffer from diarrhea or other intestinal problems. The causes range from feed changes to parasite infestations to inflammatory bowel diseases.

Content

Important laboratory values (reference values, normal values) and their interpretation in the blood of healthy cats can be found here:

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The digestive system of the cat – structure and function

To better understand gastrointestinal problems, it is helpful to have an overview of the cat’s digestive system. The cat is a carnivore. Accordingly, its digestive tract is relatively short in relation to its body size, as meat-based food is relatively easy to digest. Digestion in cats only begins in the stomach, unlike in humans, where digestive enzymes are already present in saliva.

Stations of the Digestive Tract:

  • Stomach: The food is swallowed in pieces without chewing. In the stomach, it is mixed with highly acidic gastric juice, which contains, among other things, enzymes for protein and fat digestion (pepsin, gastric lipase).
  • Duodenum: From the stomach, the chyme is passed in portions into the small intestine (starting with the duodenum). There, bile juice from the gallbladder neutralizes the gastric acid, and the pancreas supplies digestive enzymes (trypsin, lipase, etc.) – however, the cat produces very little amylase for carbohydrate digestion. This explains why high proportions of carbohydrates in cat food are not very useful, as cats can only break them down inadequately.
  • Small intestine: The small intestine is the main site of nutrient absorption (resorption); its mucous membrane forms an enormous surface through villi, through which broken-down nutrients enter the blood.
  • Large intestine: In the subsequent large intestine, mainly water is extracted from the food pulp. Indigestible residues are collected in the rectum and finally excreted through the anus.

The Role of the Intestinal Flora:

Countless microorganisms live in the entire digestive tract – especially in the large intestine – which together form the gut microbiome (formerly “intestinal flora”). These bacteria and other microbes perform important tasks: They help with:

  • Breakdown of nutrients,
  • produce vitamins,
  • train the immune system and
  • protect against disease-causing germs.

A healthy intestinal flora promotes digestion, supports nutrient absorption and contributes to normal bowel movements. If the microbiome gets out of balance, this can lead to digestive disorders and health problems.

A friendly young dog and a small cat lying together on a blue blanket

Here you will find all diseases from A to Z in cats.

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Acute vs. chronic gastrointestinal problems

Gastrointestinal diseases in cats can be roughly divided into acute and chronic problems, which is crucial for diagnosis and therapy:

  • Acute gastrointestinal problems: They occur suddenly and develop rapidly. Typical examples are acute gastroenteritis (e.g. due to spoiled food or an infection) or a sudden episode of diarrhea and vomiting after a feed change. Acute symptoms can be severe – such as repeated vomiting in a short time or constant diarrhea – but often lead to improvement within a few days, either spontaneously or through simple symptomatic treatment.

However, it is important not to trivialize acute symptoms. If a cat vomits persistently, has diarrhea, or refuses food for more than 24 hours, a veterinarian should be consulted; in the case of bloody vomiting or feces, even immediately. Untreated, acute gastrointestinal problems can quickly lead to dehydration and electrolyte imbalances, which can be life-threatening, especially for young or already weakened animals.

  • Chronic gastrointestinal problems: Chronicity is generally considered when symptoms recur over weeks or months or do not disappear completely. Frequent chronic vomiting (e.g. several times a week) or chronic diarrhea over several weeks are warning signs. Such longer-term digestive problems often indicate an underlying disease, such as chronic enteropathy. These include:
    • inflammatory bowel disease (IBD – Inflammatory Bowel Disease) and certain
    • feed intolerances. Also
    • organ diseases (such as of the pancreas or thyroid gland) can cause chronic digestive disorders.

Chronic problems often lead to weight loss, poor coat condition and nutrient deficiencies if not treated adequately. The challenge for cat owners is to recognize creeping changes at all – cats compensate for a long time and often show symptoms subtly. Therefore, it is better to seek veterinary advice early on before treatable acute problems become chronic conditions.

Causes of gastrointestinal problems in cats

Digestive problems in cats can be triggered by a variety of causes. Often, several factors play together. Basically, the causes can be divided into infectious (caused by pathogens) and non-infectious causes, whereby chronic diseases and systemic factors can also play a role.

Typical gastrointestinal diseases in cats have many possible causes:

  • Feed changes or feed intolerances can lead to soft stools, vomiting after eating or flatulence.
  • Parasite infestation (e.g. worms, giardia) is a common cause of persistent diarrhea, especially in young cats.
  • Viruses, such as the feline Parvovirus (panleukopenia) or bacterial pathogens (clostridia, salmonella), can trigger severe gastroenteritis.
  • Foreign bodies in the gastrointestinal tract cause vomiting, constipation or acute abdominal pain.
  • Chronic diseases such as Inflammatory Bowel Disease (IBD) or pancreatitis are associated with recurrent vomiting and weight loss.

The following explains the most important cause areas:

Parasite Infestation of the Digestive Tract

Parasites are among the most common triggers of diarrhea and vomiting, especially in young cats. Worms such as roundworms (Toxocara cati), hookworms or, more rarely, tapeworms colonize the intestine and can cause inflammation, nutrient loss and mucous membrane irritation. In case of severe worm infestation, one sometimes sees bloated bellies in young animals or also vomited worms. Single-celled intestinal parasites (protozoa) are also significant – for example, Giardia and coccidia cause sometimes severe diarrhea in cats (mainly in young cats or immunocompromised animals), often with foul-smelling, slimy feces. Parasites usually enter the body by ingesting infectious eggs or cysts from the environment (e.g. by sniffing/licking contaminated feces or through prey animals). Especially free-roaming cats easily get infected again and again. A chronic giardia infection can lead to intermittent (recurrent) diarrhea and weight loss. Regular stool examinations and deworming are therefore essential for prevention (see prevention). Parasite infestation can be treated predominantly well, for example by deworming (anthelmintics) or antiprotozoals – but untreated, parasites can lead to severe weakening, especially in young animals.

Viral Infections

Various viruses can affect the gastrointestinal tract in cats and trigger digestive symptoms. The most feared is:

  • Feline panleukopenia, caused by a parvovirus. It leads to severe diarrheal disease with bloody diarrhea, vomiting and high fever and is often fatal without intensive treatment – fortunately, there is an effective vaccination against it (see prevention). Other viruses with intestinal involvement are e.g.
  • Feline Coronavirus (FCoV), which can cause mild diarrhea and occurs mainly in multi-cat households. In rare cases, FCoV can mutate to the dreaded FIP (feline infectious peritonitis), which, however, represents a systemic disease.
  • Rotaviruses and astroviruses have also been detected in connection with diarrhea in cats, especially in young animals or in animal shelters, but play a rather subordinate role. Also the
  • Feline Herpesvirus (FHV-1) can indirectly cause gastrointestinal problems; primarily it leads to respiratory infections, but the general infection and loss of appetite can secondarily affect the intestine.

Viral causes of diarrhea are often difficult to treat specifically – usually the therapy is limited to symptomatic measures (fluid, warmth, support) and possibly antibiotics to prevent secondary infections. All the more important is prevention through vaccinations, if available.

Bacterial Infections

Bacteria as primary triggers of gastrointestinal diseases are less common in cats than parasites, but can become relevant especially in certain environments (e.g. animal shelters or with raw food).

  • Salmonella can be ingested through contaminated food (such as raw poultry) and lead to acute diarrhea, fever and vomiting; some cats, however, show only mild symptoms, but carry the bacteria and excrete them (risk also for humans).
  • Campylobacter and certain
  • toxin-forming Coli strains are other possible bacterial diarrhea pathogens.
  • Clostridium perfringens is present in the intestine of many cats and its toxins can trigger diarrhea in sensitive animals.

Bacterial gastroenteritis often leads to severe diarrhea with mucus and possibly blood, sometimes accompanied by fever. The treatment is either symptomatic, depending on the severity, or – in severe cases or detection of an invasive pathogen – with antibiotics.

However, the use of antibiotics should be very targeted, as they can significantly disrupt the gut microbiome (see section on the microbiome) and promote the development of resistance. Often it is more important to compensate for the loss of fluid and electrolytes and relieve the intestine through diet than to give a broad-spectrum antibiotic immediately. A special form of bacterial problem is antibiotic-associated dysbiosis, in which the normal intestinal bacteria are decimated after antibiotic treatment and e.g. Clostridium difficile can predominate – this can lead to severe diarrhea. Here, probiotics can be helpful in convalescence (more on this later).

Nutritional Causes (Food and Feeding Errors)

Nutrition plays a central role in digestive problems. Often it is not infections, but feeding errors that trigger acute gastrointestinal disturbances.

  • Sudden feed change, for example, can cause diarrhea in sensitive cats, as the intestinal flora and digestive enzymes cannot immediately adjust to the new composition. Therefore, feed changes should always be made gradually over several days.
  • Unusual or unsuitable food (e.g. heavily spiced leftovers or milk in lactose-intolerant adult cats) often leads to diarrhea or vomiting.
  • Spoiled food or waste (which some free-roamers “snack”) contains toxic bacterial products that can lead to acute gastroenteritis – colloquially one also speaks of food poisoning. Likewise can
  • Overfeeding or very large meals that overload the stomach and trigger vomiting. Cats naturally have rather small stomachs and take in many small prey animals throughout the day in the wild. If, on the other hand, they get rare but very large portions, it can lead to gastric distension and regurgitation (backflow). Also, some cats gulp down their food hastily (often in multi-cat households out of food envy) – thereby a lot of air is swallowed, which can lead to belching or vomiting shortly after eating. Anti-gulping bowls or the distribution of the food ration over several small meals help here.
  • Feed intolerances: A special case of nutrition-related problems are intolerances to certain feed components. Some cats react e.g. sensitively to a high crude fiber content or to certain additives. At a
  • At a feed allergy, in turn, there is an immune-mediated reaction to a protein in the food (common allergens are e.g. beef, fish or cereal gluten). Such cats show chronic symptoms such as recurrent diarrhea, vomiting and often also skin problems (itching). The diagnosis of a food allergy is made by an exclusion diet with a novel protein source or hydrolyzed food for at least 6–8 weeks. If the symptoms improve significantly, this confirms the feed reaction. Afterwards, a suitable hypoallergenic diet food is usually chosen as a permanent diet.

Overall, the following applies: High-quality, well-tolerated food without unnecessary additives and a species-appropriate feeding routine are cornerstones for a healthy cat stomach.

Toxic Substances and Medications

Cats react sensitively to many toxins and also to some medications, which often manifests itself first in gastrointestinal symptoms. If cats have eaten e.g. spoiled food, chemicals or poisonous plants for them, it often comes to acute vomiting and diarrhea, as an attempt of the body to get rid of the harmful substances. Some

  • Household poisons such as antifreeze (ethylene glycol) or certain
  • Houseplants (e.g. Dieffenbachia) trigger, in addition to systemic effects, also strong irritations in the digestive tract.
  • Medicines can also cause gastrointestinal problems: A classic example is non-steroidal anti-inflammatory drugs (NSAIDs) – even in small doses, they can cause gastric mucosal irritation up to ulcers in cats. Also
  • Antibiotics can trigger diarrhea as a side effect because they disrupt the intestinal flora. Certain
  • Deworming or spot-on agents taste extremely bitter when the cat licks them off, which often causes immediate frothy vomiting (here it is more the bitter taste than a poisoning).
  • Heavy metals such as lead (e.g. from lead poisoning when licking old paints) also show with vomiting, abdominal pain and possibly Blood in the stool.

The list of toxic causes is long – it is important to remember this when a cat suddenly shows gastrointestinal symptoms, especially if there was possible access to something toxic. The treatment consists, depending on the substance, of detoxification measures (e.g. activated charcoal, antidotes) and intensive symptomatic care.

Hairballs (Trichobezoars) and Foreign Bodies

  • Hairballs are a common cause of vomiting in cats. Cats spend a lot of time grooming and swallow hair, which can collect in the stomach to form hairballs. Individual hairs normally pass through the intestine, but larger hairballs (trichobezoars) can irritate the stomach and intestines. Typically, the cat regurgitates the hairball – the classic “wool ball vomiting”. Sometimes, however, hairballs get into the intestine and can cause partial obstructions there, which can lead to recurrent vomiting, constipation or thin, hairy feces. Apart from hair, also
  • Foreign bodies (anything the cat cannot digest) can cause stomach and intestinal problems. Young, playful cats, for example, like to chew on threads, gift ribbons, rubber bands, or small toys. If something like this is swallowed, it can lead to an intestinal obstruction in the worst case. Linear foreign bodies (such as threads) are particularly dangerous because they can get caught in the intestine and cause sawing damage. The first signs of a foreign body can be repeated unsuccessful vomiting, abdominal pain, loss of appetite, and constipation. If a foreign body gets stuck, surgical removal is often necessary. Smaller foreign bodies in the stomach (e.g., Christmas tinsel) can sometimes be passed by administering lubricants or hairball pastes. Prevention: Cat owners should make sure to keep dangerous small parts out of the cat’s reach and reduce hairball formation by brushing regularly.

Inflammatory Bowel Disease (IBD)

The term IBD (Inflammatory Bowel Disease) refers to a chronic inflammatory bowel disease of unknown cause, which is relatively common in cats. This leads to a constant inflammation of the intestinal wall, mostly in the small intestine, sometimes also in the large intestine, without an infectious trigger being detectable. The following are being discussed

  • Immune system malfunctions,
  • genetic factors and a
  • shift in the intestinal flora as the cause.

Cats with IBD typically show chronic vomiting, chronic diarrhea, weight loss despite a predominantly normal or even increased appetite (polyphagia), and occasionally a changing stool pattern (sometimes firm, sometimes soft). The diagnosis is tricky: First, other causes (parasites, food, etc.) must be excluded. Final certainty often only comes from an intestinal biopsy via endoscopy or laparotomy, in which inflammatory infiltrates are detected in the intestinal wall. Although IBD is not curable, it is treatable. The therapy is based on dietary measures (highly digestible diet, hypoallergenic food) and immunosuppressive drugs – usually corticosteroids (prednisolone) in the long term in the lowest possible effective dose. Vitamin B12 (cobalamin) is also often supplemented, as many IBD cats develop a deficiency due to impaired absorption. It is interesting that changes in the intestinal microbiome are often found in cats with chronic enteropathies (reduced bacterial diversity, shift in certain bacterial groups.).

Such changes are called dysbiosis. Dysbiosis could be both a cause and a consequence of inflammation in IBD. Therefore, probiotics and prebiotic therapies are also gaining interest in IBD treatment. Some studies in dogs and initial approaches in cats show that probiotics can dampen inflammatory activity. IBD usually requires lifelong care, with regular check-ups and adjustments to the therapy regimen, but many cats can achieve a good quality of life with it.

Neoplasias (Tumors of the Gastrointestinal Tract)

Tumors in the digestive tract can cause similar symptoms to IBD and are an important differential diagnosis, especially in older cats. The most common is lymphatic lymphoma of the intestine (a tumor originating from lymph cells), which often occurs in the small intestine in cats. There is an overlap between IBD and lymphoma – it is assumed that long-term IBD can turn into lymphoma in some cats.

Clinically, chronic diarrhea, vomiting, and emaciation are evident; ultrasound sometimes shows thickened intestinal loops or enlarged local lymph nodes. Other tumors such as adenocarcinomas (glandular tumors) in the stomach or intestine are less common, but can lead to chronic bloody diarrhea and pain, especially in the large intestine. Benign polyps in the intestine are rare, but could cause chronic diarrhea or irritation when prolapsing from the anus. The diagnosis of neoplasias is made via imaging (ultrasound, X-ray, computed tomography – possibly with contrast medium). A confirmed diagnosis is possible through biopsy/fine needle aspiration and subsequent histopathological examination. The therapy depends on the tumor type: Lymphomas are treated with chemotherapy or prednisolone in cats, adenocarcinomas are surgically removed if possible. The prognosis varies greatly – while some lymphatic lymphomas can be managed for months to a few years under chemo, invasive carcinomas often have a poor prognosis. It is important to also consider tumor diseases in older cats with chronic gastrointestinal symptoms in order to intervene early.

Diseases of other Organs (Secondary Causes)

The gastrointestinal tract does not work in isolation – problems in other organ systems can cause digestive problems. Some important secondary causes of vomiting/diarrhea in cats are:

  • Pancreatitis (inflammation of the pancreas): The pancreas is closely involved in digestion. An acute or chronic inflammation (not so rare in cats, often subclinical) leads to recurrent vomiting, inappetence, and abdominal pain; diarrhea is less common. Since many cats with pancreatitis also have IBD and/or inflammation of the bile ducts at the same time (this is called triaditis), the symptoms are often mixed. Pancreatitis requires special treatment (infusions, bland diet, painkillers) and can be life-threatening.
  • Hepatic encephalopathy/liver damage: Severe liver diseases can lead to vomiting because toxic metabolic products accumulate. In addition, loss of appetite often occurs. Nausea and vomiting are particularly common in hepatic lipidosis (fatty liver) as a result of inappetence. Also
  • Cholangitis (inflammation of the bile ducts) often occurs together with pancreatitis and IBD and causes diffuse digestive symptoms.
  • Chronic kidney disease (CKD): Many older cats suffer from CKD. Due to the limited detoxification, more uremic substances circulate in the blood, which can lead to vomiting due to uremia. In addition, CKD cats tend to have stomach ulcers. An early sign of kidney problems can therefore be increased vomiting, often together with weight loss and increased drinking/urination.
  • Hyperthyroidism: Overactive thyroid glands produce excess hormones, which speeds up the metabolism. Typical are a greatly increased appetite with simultaneous weight loss, but vomiting and diarrhea are also common because digestion is “overstimulated” and passage is accelerated. The thyroid gland is routinely tested in older cats with these symptoms. Treatment of hyperthyroidism (medication, iodine therapy, or surgery) usually also improves digestive symptoms.
  • Diabetes mellitus: Severe, uncontrolled diabetes (ketoacidosis) can also trigger vomiting. However, other symptoms (excessive drinking, urination, weight loss) are in the foreground here.
  • Stress: Severe stress can affect cats’ stomachs – it is not uncommon to observe that a stressed animal suddenly gets diarrhea. Stress and anxiety affect the autonomic nervous system and thus intestinal motility. Also
  • Neurological diseases (e.g., a vestibular syndrome) can trigger nausea. In addition, severe pain (including painful teeth!) sometimes leads to inappetence and vomiting due to the stress response.

This list shows how diverse the causes of gastrointestinal problems in cats are. It is often a detective challenge to determine the exact trigger – especially when several factors interact (e.g., cat with IBD who also gets parasites, etc.). A systematic diagnostic approach is therefore important in order to be able to treat the cause specifically.

Symptoms of a gastrointestinal disease

Digestive problems in cats manifest themselves through various symptoms, which can vary depending on the cause and the affected section of the digestive tract.

As a pet owner, you should pay attention to the following signs:

  • Unusual behavior such as increased grass eating, rolling around, and withdrawal can be the first signs of a disease of the stomach or intestine.
  • Vomiting (Vomitus): Occasional regurgitation of hairballs is normal in cats. Pathological vomiting is recognized by the fact that it occurs frequently (several times a day or over several days), often not only hair, but food or mucus/bile is vomited, and the cat shows signs of nausea (drooling, smacking, restlessness). Vomiting immediately after eating may indicate too hasty swallowing or irritation in the stomach; foamy vomiting on an empty stomach often indicates gastritis. Blood in the vomit (red or “coffee grounds-like”) is an alarm signal for possible ulcers or severe mucosal damage.
  • Diarrhea (Diarrhoe): Diarrhea is when the stool is mushy to liquid and is often passed more frequently. Acute diarrhea occurs suddenly, e.g., in infections or feeding errors, while chronic diarrhea persists for weeks. A rough distinction is made between small intestinal and large intestinal diarrhea: Small intestinal diarrhea manifests itself in large amounts of stool that are very liquid and often of a light color, often accompanied by weight loss. Large intestinal diarrhea (Colitis), on the other hand, shows rather small amounts of stool that can be slimy and often contain traces of blood (fresh red blood), accompanied by frequent urge to defecate and pressing. With diarrhea, the cat often cannot reach the litter box in time or accidents happen next to the litter box. Attention: Prolonged diarrhea leads to fluid loss (dehydration); electrolytes and vitamins (such as B12) can also be lost and should always be clarified by a veterinarian.
  • Loss of appetite (Inappetence) is a non-specific sign, but in connection with vomiting/diarrhea an important indication of a gastrointestinal problem. Some cats with chronic problems eat, but less enthusiastically, or they only pick certain components out of the food. Ravenous hunger, on the other hand, can occur with maldigestion/malabsorption – the cat eats a lot but does not gain weight (e.g., with parasites or hyperthyroidism).
  • Weight loss: Unintentional weight loss over weeks is an alarm sign. Especially with chronic intestinal problems (IBD, exocrine pancreatic insufficiency, chronic parasite infestation), the animals lose weight despite seemingly adequate food intake because nutrients are not properly utilized. The cat also loses weight with persistent diarrhea (water, muscle loss). Often you see a bad coat at the same time (dull, shaggy), which indicates malnutrition.
  • Abdominal pain: Abdominal pain in cats can be recognized by defensive reactions when palpating the abdomen, by a tense abdominal wall or by a curved back (protective posture / guarding posture). The cat may meow in pain or withdraw. Colic-like pain leads to restlessness, frequent changes in posture, sometimes licking on the abdomen. Pain indicates, for example, pancreatitis, a foreign body, or severe intestinal cramps.
  • Increased bowel sounds: Flatulence and flatulence (winds) are rather rare in cats, but can occur with unsuitable nutrition (very high proportion of plants) or malfermentations. A bloated abdomen in an adult cat may indicate gas accumulation or fluid accumulation (in FIP). In young cats, a potbelly often indicates worm infestation.
  • Changed defecation behavior: Frequent pressing without success in the litter box, howling meowing during defecation, or defecation in unusual places indicate constipation. This manifests itself through rare, hard defecation with pain; sometimes you only see frequent unsuccessful pressing and the cat is restless or apathetic. Long-term constipation can lead to a megacolon (dilated large intestine), which causes further symptoms such as inappetence, vomiting, and apathy. Both diarrhea and constipation can be accompanied by anal inflammation or licking at the anus.
  • Impaired general condition: In severe gastrointestinal problems, the general condition is often impaired. The cat seems apathetic or lethargic, withdraws, sleeps more.
  • Fever can occur with infectious causes (e.g., viral or bacterial gastroenteritis).
  • Dehydration: Due to the fluid loss (dehydration), the mucous membranes dry out. Other signs of dehydration are reduced skin elasticity (skin fold remains standing), dry oral mucosa, and sunken eyes. In such cases, rapid veterinary intervention is necessary.

Symptoms should always be considered in the overall picture. If a cat occasionally vomits a hairball and is otherwise cheerful, this is no cause for concern. However, if several of the symptoms mentioned occur in combination (e.g., diarrhea + vomiting + loss of appetite), or if there are clear changes in the cat’s normal behavior, clarification is important. Repeated vomiting in cats or persistent diarrhea for more than 48 hours should always be clarified by a veterinarian.

Diagnosis: How are gastrointestinal problems examined?

The diagnosis of gastrointestinal problems requires a systematic approach to find the cause of the gastrointestinal symptoms.

These include:

  • Stool examination (parasitology, bacterial culture, PCR for Giardia)
  • Blood test (organ parameters, pancreas, inflammatory markers)
  • Ultrasound examination to visualize intestinal wall changes, foreign bodies, or enlarged lymph nodes
  • In chronic cases: Biopsy from stomach/intestine under sedation to clarify IBD or tumors

Typically, the diagnostics include the following steps and methods:

Medical History (Anamnesis) and Clinical Examination

At the beginning there is a thorough anamnesis (collection of the medical history). The veterinarian will ask:

  • Since when the symptoms exist,
  • Frequency of vomiting/diarrhea,
  • Appearance of the stool/vomit,
  • whether food changes took place,
  • which feeding is generally done,
  • whether the cat has free access,
  • whether medications were administered,
  • how is the deworming and vaccination protection as well as about
  • possible stress factors in the cat’s environment and other details.

For the veterinarian, this information is essential to narrow down probable causes – e.g., unvaccinated young cats with bloody diarrhea are more likely to indicate panleukopenia, while older cats with weight loss and vomiting are more likely to be examined in the direction of chronic bowel disease/organ problem.

A thorough clinical examination follows. The:

  • Body temperature measured (fever?),
  • the mucous membranes inspected (moisture, color), and
  • the hydration status checked. Through
  • Palpation of the abdomen can detect painful areas, intestinal changes, or suspected foreign bodies. Also, the veterinarian*in
  • will pay attention to noises in the intestine (with the stethoscope on the abdomen) – excessive bowel sounds could indicate diarrhea, missing sounds indicate intestinal paralysis.
  • The oral cavity is checked (foreign bodies under the tongue? Dental problems?) and also the anal area (contamination, worms visible, pain reaction).

This step often provides important clues: For example, yellowish mucous membranes indicate a liver problem, stinking foul breath can indicate uremia in kidney failure, and very thin, dehydrated cats with shaggy fur direct suspicion towards chronic malabsorption.

Laboratory Diagnostics: Blood and Stool Tests

After the clinical examination, laboratory tests are the next pillar of diagnostics. These include:

  • Blood tests: A complete blood count and blood chemistry profile can provide general information. Inflammatory cells in the blood (high leukocytes) indicate infections or inflammatory conditions; anemia could occur in chronic disease. Organ values are checked: kidney values (urea, creatinine), liver values, and electrolytes (sodium, potassium) are important to see if there are secondary effects or primary organ problems (e.g., dehydration leads to increased hematocrit and altered electrolytes). Specific to the digestive tract, there is the cPLI/fPLI test (canine/feline pancreatic lipase immunoreactivity) for the diagnosis of pancreatitis – in suspicious cases, this value is measured because pancreatitis often accompanies gastrointestinal symptoms. In chronic diarrhea, cobalamin (vitamin B12) and folate in the blood are often determined; a deficiency of B12 is an indication of small intestinal malabsorption (often with IBD or chronic parasitic infestation) and must be treated. If hyperthyroidism is suspected (older cat with weight loss, diarrhea), the T4 (thyroxine) level in the blood is measured. Blood tests can also be examined for inflammatory markers (such as fibrinogen or SAA) to quantify acute inflammation.
  • Fecal examinations: A parasitic fecal examination is mandatory in case of diarrhea. As a rule, a pooled fecal sample from 2 to 3 days is examined in the laboratory for worm eggs (microscopically) and Giardia (antigen test or microscopy). Even if the cat is regularly dewormed, this should be checked – some types of worms are not covered by every drug, and resistances exist. In addition, a bacteriological fecal profile can be useful, e.g., if salmonellosis is suspected or if several cats in the household are affected. In this case, a fecal culture is created and examined for pathogenic germs. PCR tests can be used to detect pathogens such as Tritrichomonas foetus (protozoa occurring in cats and primarily relevant in pedigree cat breeding), which are easily overlooked under the microscope. Certain viruses (FCoV, rotavirus) can also be detected by PCR in the feces, which can be epidemiologically interesting in multi-cat households or animal shelters. In chronic diarrhea with suspected dysbiosis, a gut flora screening can also be performed in special laboratories to estimate useful vs. harmful bacteria – in practice, however, this is still rarely used routinely.
  • Urine examination: This is often also part of the basic check, especially to avoid overlooking other diseases. For example, excessive thirst/polyuria (e.g., in kidney disease or diabetes) can lead to dehydration and secondary gastrointestinal symptoms. If something is noticeable in the urine sample (glucose in the urine → diabetes, concentrated urine → dehydration), this helps with the overall assessment.

Laboratory diagnostics make it possible to uncover systemic problems and to narrow down or rule out certain causes. For example, if blood and fecal examinations in a chronically vomiting cat are completely unremarkable, a primary gastrointestinal disease (such as IBD or an anatomical problem) moves more into focus.

Imaging Diagnostics: X-ray and Ultrasound

Imaging procedures can be used to visualize the inside of the abdomen in order to detect structural changes, foreign bodies, or organ changes.

  • X-ray examination:

    An abdominal X-ray can provide indications of foreign bodies (metal-dense objects, contrast differences), an intestinal obstruction (distended intestinal loops with gas-fluid levels), or greatly enlarged organs. Bones or dense objects (such as a swallowed fishhook) are clearly visible. However, many soft tissues are superimposed in the X-ray image. In some cases, a contrast X-ray is performed: the cat is given a contrast agent (barium) that glows on the X-ray and lines the digestive tract. In this way, e.g., passage obstructions, ulcerations, or anatomical abnormalities can be detected. However, this is now often displaced by ultrasound.

  • Ultrasound (sonography):

    The ultrasound examination of the abdomen is very productive in gastrointestinal problems. It allows the assessment of organ structures in real time. An experienced veterinarian can measure the wall thickness of the stomach and intestine – thickened intestinal walls indicate chronic inflammatory conditions or tumors. You can see the layering of the intestinal wall; the loss of normal layering can be an indication of lymphomas. Foreign bodies (e.g., a thread that meanders in the intestine or a piece of rubber in the stomach) can often be visualized by ultrasound. The pancreas can be assessed (often enlarged and hypoechoic in pancreatitis, with fluid around it). The liver and kidneys are also assessed to have a comprehensive picture. In addition, the ultrasound can show whether there is free fluid in the abdominal cavity (e.g., in FIP). Samples are often taken specifically under ultrasound guidance: In the case of suspicious intestinal sections or lymph nodes, a fine needle aspiration or biopsy can be performed on a trial basis, which can be very useful in the diagnosis of IBD vs. lymphoma. Overall, ultrasound is almost indispensable in chronic cases to plan the further steps (endoscopy vs. surgery).

Endoscopy and Biopsy

In some cases, it is necessary to look directly into the digestive tract. This is done by means of endoscopy – a camera probe that is inserted through the mouth or anus:

  • Gastroscopy: Via the oral cavity, a flexible endoscope can be advanced into the esophagus, stomach, and upper small intestine under anesthesia. In this way, e.g., mucosal changes in the stomach can be detected (redness, stomach ulcers, foreign bodies) and tissue samples (biopsies) can be taken. Biopsy is particularly important for distinguishing between IBD and lymphoma or for detecting Helicobacter bacteria in the gastric mucosa. Smaller foreign bodies can also be removed directly with the endoscope, if accessible (e.g., a band in the stomach).
  • Colonoscopy: Similarly, the large intestine and a piece of the lower small intestine (ileum) can be examined endoscopically from the anal side. This is done if there is chronic large bowel diarrhea or blood in the stool. Inflammatory conditions, polyps, tumors, or parasites (e.g., whipworms, if present) are recognized directly. Here, too, biopsies are central, e.g., to distinguish between chronic colitis and colon cancer.

Endoscopy is minimally invasive and very helpful, but requires anesthesia and good preparation (bowel cleansing for colonoscopy). Not every small animal veterinarian has an endoscope – in such cases, a referral to a specialist can be made. Alternatively, especially if endoscopy is not possible or not sufficient (e.g., the gastroscopy does not reach all small intestinal sections), an exploratory laparotomy (abdominal surgery) can be considered. The surgeon can then directly inspect the organs, remove palpable tumors, and take targeted biopsies of the intestine, stomach, liver, lymph nodes, and pancreas. This is more invasive, but often provides the definitive diagnosis in unclear chronic cases.

Other Special Tests

Some additional diagnostic steps are useful depending on the suspected diagnosis:

  • Elimination diet: As mentioned above in the causes, an elimination diet is performed if a food allergy is suspected. This is very important diagnostically, as a clear improvement under the diet practically confirms the diagnosis.
  • Allergy tests: Blood tests or intradermal tests for food allergies are not very reliable in cats, but can be done in addition to skin symptoms. However, this usually does not replace the elimination diet.
  • Motility tests: In special cases, the gastric emptying time or intestinal transit time can be measured (e.g., via markers in the X-ray) if a motility disorder is suspected.
  • Neurological examinations: If it is suspected that vomiting is triggered centrally (in the brain), e.g., by brain disease, neurological examinations or imaging of the head would be indicated.

Despite all modern diagnostics, it remains a fact that in some cases no clear cause is found – this is then referred to as idiopathic gastroenteropathy. However, it is important to rule out all serious causes before settling for this. Once the suspected cause has been identified, treatment can be initiated in a targeted manner.

Therapy: What helps with stomach problems in cats?

The treatment of gastrointestinal diseases in cats depends on the cause and severity of the disease.

In milder cases, a diet food, possibly with highly digestible proteins, bland food (e.g., chicken, rice) and the addition of probiotics are often sufficient. In the case of parasites, a targeted deworming treatment is necessary.

In many cases, a combination of symptomatic treatment (to relieve acute symptoms) and causal treatment (to eliminate the underlying cause) is necessary. The most important building blocks of therapy are presented below:

Stabilization and Symptomatic Treatment

Especially in acute and severe cases, the first priority is to stabilize the cat’s condition and combat symptoms.

  • Fluid therapy: Vomiting and diarrhea quickly lead to fluid and electrolyte losses. If there are signs of dehydration, the cat must be rehydrated. Mild cases can be treated by oral rehydration (e.g., giving water or electrolyte solutions into the mouth, provided there is no more vomiting). In moderate to severe cases, the veterinarian will initiate infusion therapy – usually intravenously, in mild cases possibly also subcutaneously. The infusion replaces lost water, sodium, potassium, and chloride and often significantly improves the cat’s condition within a short time.
  • Dietary rest (food break): Traditionally, it was often recommended to let the cat fast for a certain time in case of vomiting/diarrhea in order to relieve the stomach and intestines. Currently, however, fasting is approached with caution: A short food break of 12 to 24 hours can be useful in severe vomiting, but fasting should not last longer than 1–2 days, as otherwise the intestinal villi will atrophy and the cat’s metabolism will suffer (especially in overweight animals, there is a risk of lipidosis). As soon as vomiting is under control, refeeding should be started early, initially in very small portions.
  • Antiemetics (anti-vomiting drugs): In case of uncontrollable vomiting, the veterinarian can inject an antiemetic or give it as a tablet. Maropitant (Cerenia) is a commonly used drug that blocks the vomiting center. Metoclopramide (Paspertin) can also be used, but works less well in cats. Antiemetics provide relief and allow the cat to retain fluid/diet.
  • Gastrointestinal protection: If gastritis is suspected or if acid is vomited, a stomach protection preparation can be useful. Proton pump inhibitors such as omeprazole reduce stomach acid and give the mucous membrane an opportunity to heal. Antacids or sucralfate (binds to damaged mucosal sites) are also used, especially if stomach ulcers are suspected (e.g., in NSAID damage or uremic gastritis). However, it should be noted that, e.g., omeprazole has been shown to affect the intestinal flora. These agents should therefore be used with caution.
  • Antidiarrheals: Medications directly against diarrhea are limited in cats. Motility inhibitors (such as loperamide) are rarely given because of possible side effects. Instead, attempts are made to influence diarrhea through diet and probiotics. Kaolin-pectin preparations or montmorillonite (healing earth) can improve consistency by binding toxins and solidifying the stool. In bloody diarrhea or colitis, veterinarians sometimes give antispasmodic drugs (Buscopan) or 5-ASA suppositories (mesalazine) for large intestinal inflammation. But it is important to note that diarrhea is a cleansing mechanism; complete suppression can be undesirable – instead of constipating, causes should be treated and sufficient fluid should be supplied.
  • Pain management: Severe abdominal pain, such as in pancreatitis or obstruction, requires pain medication. Opioids such as buprenorphine are used to spare the cat suffering and reduce stress (which in turn promotes healing). NSAIDs are contraindicated in gastrointestinal problems (can worsen the situation), so veterinarians resort to opioid analgesics or, in some cases, spasmolytics.

Diet Management and Nutritional Measures

The right diet is often the key to recovery. Depending on the situation, different dietary approaches come into play:

  • Bland diet for acute problems: After a short fast or even in parallel, the cat should receive an easily digestible diet that is gentle on the stomach and intestines. Such a bland diet is characterized by moderate fat content, high-quality, easily digestible proteins and carbohydrates, and usually a relatively low fiber content. Many veterinarians recommend cooked chicken with rice or special commercial diet food for gastrointestinal patients. It is important to feed in small portions and offer them frequently throughout the day – e.g., 4–6 mini-meals instead of two large meals. This puts less strain on the digestive tract, reduces nausea, and improves nutrient absorption. In cats, bland food must also be palatable, as not eating can quickly lead to lipidosis. Warm, moist food is often preferred.
  • Reconstruction after diarrhea: Once the acute diarrhea has subsided, you should not abruptly switch back to the old food. A gradual increase in the amount of food and a gradual transition to normal food over 5–7 days has proven successful. The intestine needs some time to recover. In some cases (e.g., after severe gastroenteritis), it is recommended to give a easily digestible diet food for a few weeks before returning to the routine.
  • Therapeutic diets for chronic diseases: In diagnoses such as IBD or chronic pancreatitis, special diets are often a central component of long-term therapy. For IBD cats, a diet with highly digestible ingredients and an increased protein content has proven successful in preventing the loss of muscle mass and supporting impaired digestion. If food allergies play a role, hydrolyzed diets or novel protein diets (e.g., with rare protein sources such as rabbit, horse, game) are used. These can significantly reduce inflammatory conditions by removing the immunological trigger. Interestingly, the fat content of the food in cats is not as critical for gastric emptying as in dogs – one study showed that the fat content had no major impact on chronic diarrhea in cats. Therefore, it is not necessarily necessary to feed a low-fat diet, as long as the food is well tolerated. High-fiber diets (fiber) can be helpful in large intestinal problems, especially soluble fibers such as psyllium, to regulate stool consistency. In the case of constipation or megacolon, a high fiber content is often combined with plenty of fluid, or also easily fermentable fibers to keep the stool soft.
  • Feeding in pancreatitis and EPI: In acute pancreatitis, strict fasting was previously recommended; today we know that early feeding in small amounts promotes intestinal health. The food should be very easily digestible. In exocrine pancreatic insufficiency (EPI, very rare in cats), pancreatic enzymes must be added to the food so that nutrients can be digested at all, and mostly low-fat diets are fed.
  • Appetite stimulants: If cats absolutely do not want to eat, in addition to offering different types of food (sometimes they like baby food-like consistencies or particularly odorous food), appetite stimulants can also be used. Mirtazapine is a commonly used drug that stimulates appetite in cats. However, this should only be used after stabilization and on the advice of the veterinarian.

Diet management often requires some patience and fine-tuning. Every cat is individual – what one tolerates well may be less successful for the other. Close monitoring during dietary changes and monitoring of the cat’s body weight and condition are important.

Drug and Causal Therapy

In addition to general stabilizing treatment and diet, the causes must be treated directly – if possible:

  • Deworming and parasite treatment: If parasites are detected or suspected, targeted deworming should be carried out. Many veterinarians deworm cats with diarrhea as a precaution, even if there is no evidence, as some parasites can be difficult to detect. Preparations with a broad-spectrum effect against roundworms and Giardia are often combined. For Giardia, e.g., fenbendazole or metronidazole is given over several days. Important: Check the stool again after treatment to ensure success.
  • Antibiotics: Antibiotic therapy is indicated if a bacterial infection has been identified (e.g., severe Salmonella diarrhea with risk of sepsis) or if there is a risk of secondary infection (e.g., in panleukopenia, where the intestinal barrier is destroyed). A therapeutic trial with tylosin or metronidazole can also be performed for chronic enteropathy of the “antibiotic-responsive” type (as occurs in dogs; less described in cats). In cats, metronidazole has not only antibacterial/antiprotozoal effects, but also immunomodulatory effects, which is why it was often given for IBD in the past – however, due to the effects on the microbiome and possible side effects, it should not be used uncritically in the long term. In general, antibiotics should be used as specifically and briefly as necessary to avoid resistance and dysbiosis.
  • Immunosuppressants: In immune-mediated diseases such as IBD, corticosteroids are the treatment of choice. Prednisolone is given in a relatively high initial dose and then slowly reduced to a maintenance dose. Most cats respond well to this: the vomiting stops, the diarrhea improves, and weight increases. In severe cases or in cases of steroid intolerance, chlorambucil (a mild chemotherapeutic agent) or newer immunomodulators can also be used. Cyclosporine has also been used successfully in feline IBD. It is important to adjust the dose to minimize side effects (e.g., diabetes from steroids) and to monitor the success of the therapy via symptoms and, if necessary, follow-up examinations.
  • Vitamin and nutrient supplementation: Many cats develop deficiencies with long-standing gastrointestinal disturbances. A well-known example is vitamin B12 deficiency in chronic small intestinal disease – this is compensated for by regular B12 injections, which often further improves intestinal health, as B12 is important for the regeneration of the intestinal mucosa. Likewise, potassium can be too low in chronic diarrhea or in cats with chronic kidney disease and must be supplemented (potassium supplements). If the cat eats very little, high-calorie pastes or tube feeding may be necessary temporarily to provide calories and nutrients.
  • Probiotics and prebiotics: An increasingly used causal therapy – especially for restoring the intestinal flora after antibiotics or diarrhea – are probiotics (living “good” bacteria) and prebiotics (fiber that promotes beneficial bacteria). Probiotics can restore the intestinal flora to balance and accelerate healing. For example, certain probiotics have been shown to significantly shorten the duration of diarrheal diseases in cats. More on this in the section on probiotics.
  • Specific medications: Depending on the diagnosis, other agents may be considered. For Giardia, for example, metronidazole or fenbendazole. Ronidazole helps with Tritrichomonas infection (occurs mainly in young cats from breeding). In the case of motility disorders, prokinetics such as cisapride could be used (e.g. in chronic constipation due to megacolon). In the case of ulcerations in the large intestine (ulcerative colitis), sulfasalazine can help, but is dosed carefully because of possible side effects.

Drug therapy should always be tailored to the individual animal. Long-term therapy is often necessary, especially for chronic diseases. Here it is important to find a regimen that is effective but has as few side effects as possible. Regular check-ups (blood values with long-term steroid use, stool checks, weight control) are important to adjust the treatment.

Surgical interventions

In certain situations, a surgical intervention is unavoidable:

  • Foreign body surgery: A complete intestinal obstruction or dangerous foreign bodies (e.g. needle with thread) require rapid surgical removal. The abdomen is opened (laparotomy) and the object is removed, if necessary a damaged part of the intestine must be resected. After the surgery, the cat is intensively cared for (infusion, slow feeding build-up). The prognosis depends on how long the foreign body has been causing problems and whether parts of the intestine have already died.
  • Tumor surgery: Well-defined tumors (e.g. a single intestinal adenocarcinoma) should be surgically removed if possible. Often a segment of the intestine is removed and the ends are sewn back together (intestinal anastomosis). In the case of large intestinal tumors, it can be challenging to maintain continence. After removal, further therapy (chemo) may follow depending on the tumor.
  • Biopsy surgery: Sometimes surgery is also performed to confirm diagnoses, for example if no biopsy could be obtained from deep intestinal sections by means of endoscopy or if, at the same time, e.g. an enlarged lymph node sample is to be taken. In such cases, an exploratory operation can clarify whether, for example, IBD or a lymphoma is present, and samples can be taken specifically from the liver, intestine, pancreas (important in suspected triaditis).
  • Correction of anatomical problems: Rarely, anatomical problems such as intussusception (invagination of the intestine) may require surgery. Also in megacolon, if medication no longer helps, a subtotal colectomy (removal of a large part of the large intestine) is performed as a last option to give the cat back its quality of life.

Surgical therapies naturally carry a higher risk and are only used when the benefit justifies it. Thanks to modern anesthesia and pain therapy, however, many older cats also survive such procedures well, provided they go into the surgery stabilized. Postoperatively, good pain management and monitoring are important so that no complications occur (postoperative bleeding, peritonitis, etc.).

Course and prognosis

The prognosis for gastrointestinal disturbances depends very much on the cause. Acute uncomplicated gastroenteritis (e.g. due to feeding errors) usually improves within days and has a very good prognosis – often supportive therapy is sufficient and the cat is quickly fit again. Severe infections (parvovirus) have a guarded to poor prognosis despite treatment, but can be survived with intensive management. Chronic diseases such as IBD require long-term therapy, but most patients have a good quality of life and lifespan if treatment is successful. Tumor diseases vary – an intestinal lymphoma, for example, can go into remission with chemo, but often comes back; a completely surgically removed small tumor, on the other hand, can be cured. It is important to ensure therapy adherence (owner participation): e.g. consistently adhere to diet, give medication on time, attend follow-up appointments. With good care, many cats with gastrointestinal disturbances can recover completely or at least live stably with a chronic disease.

After the detailed consideration of treatment methods, we now turn to the special focus: the intestinal microbiome and the use of probiotics. These play an increasing role in both the prevention and treatment and maintenance of the health of the digestive tract, supported by current scientific findings.

Biomedical basics: The cat's intestinal microbiome

In recent years, research has devoted much attention to the intestinal microbiome – i.e. the entirety of the microorganisms living in the intestine. In cats, too, it is becoming clear that the microbiome is closely linked to digestive health and general health.

Function of the Intestinal Microbiome

The digestive tract of the cat harbors billions of bacteria as well as fungi, protozoa and viruses that live together in a complex ecosystem. This microbiome performs numerous beneficial functions for the host – i.e. the cat:

  • Help with digestion: Intestinal bacteria utilize food components that the cat itself cannot break down well. In particular, fiber (plant fibers) is fermented by certain bacteria. This produces short-chain fatty acids (e.g. butyric acid), which serve as energy for the intestinal cells. In this way, the cat gains additional energy and nutrients from the food via the microbiota. Some bacteria also produce vitamins (such as B vitamins, vitamin K) in the intestine.
  • Protection against pathogens: A healthy microbiome acts as a barrier against invading germs. The good bacteria compete with pathogenic (disease-causing) microbes for nutrients and attachment sites on the intestinal wall. They also produce substances that are harmful to pathogens, e.g. organic acids, bacteriocins (specific proteins or peptides as metabolic products of bacteria) or peroxides. Thus, they prevent harmful germs from multiplying strongly. This is called the colonization resistance effect – the native flora repels invaders.
  • Support of the immune system: A large part of the immune system is located in the intestine (gut-associated lymphoid tissue, GALT). The intestinal microbiota plays a crucial role in the development of the immune system – especially in young cats, it helps to build a stable immune system. Constant interactions between bacteria and immune cells teach the body to distinguish friend from foe. Some intestinal bacteria stimulate the production of anti-inflammatory messengers and promote immune tolerance. At the same time, the immune system is ready in case pathogenic germs get out of hand.
  • Maintenance of intestinal structure: The presence of the microbiota promotes intestinal barrier function. Bacterial products such as butyrate nourish the intestinal epithelial cells and promote their regeneration. In addition, the commensals keep mucus production going and thus strengthen the mucus layer that lines the intestinal wall. All this contributes to the intestine remaining tight and no harmful substances entering the body uncontrollably.
  • Metabolic effects: Newer research shows that the microbiome also has an influence on metabolism. It plays a role in weight regulation, influences fat metabolism and even blood sugar levels. Changes in the microbiome can be associated with overweight. In the case of overweight, however, it is unclear whether the altered flora contributes to weight gain or is simply a consequence of the altered metabolic situation. Diabetes, liver diseases, etc. could also have repercussions on the intestinal flora, as metabolic products and digestive juice composition change. Connections between intestinal bacteria and other organ systems have also been found – such as the gut-brain axis, in which intestinal bacteria influence the brain and behavior via nerve signals and metabolic products.

In summary, a diverse and balanced intestinal microbiome contributes significantly to the health of the cat. It is a silent player that supports digestion and immune defense and protects the body from harmful organisms. A disturbance of this balance can consequently have considerable effects.

Factors that Influence the Intestinal Microbiome

The microbiome is not a rigid system – it is subject to influences from inside and outside. Important factors that influence the composition and health of the intestinal flora are:

  • Nutrition: The type of food has a direct influence on the intestinal bacteria composition. Fiber promotes certain beneficial bacteria, while very protein-rich, low-fiber diets (as is common in cats) favor a different flora. Sudden changes in feed can temporarily disrupt the flora. A balanced, high-quality diet, on the other hand, helps to maintain a stable, diverse microbiota. Prebiotics (certain fibers such as inulin, fructo-oligosaccharides) in the feed can also specifically promote positive germs.
  • Age and development: Newborn kittens are born almost germ-free and are colonized with bacteria from the mother and the environment in the first days of life. The first milk (colostrum) also provides immune factors that help to establish a healthy microbiome. Studies show that the microbiome changes significantly in the first weeks and reaches relative stability from about the age of a few months. Young animals still have less diversified intestinal communities. In old age, diversity can decrease again; older cats tend to have simpler microbial communities, which may increase their susceptibility to gastrointestinal disturbances.
  • Genetics: There is evidence that genetic predisposition influences the intestinal flora. In dogs, it has been shown that closely related animals have more similar microbiomes than unrelated animals despite different environments. In cats, too, the breed or ancestry could co-determine certain flora characteristics, although environment and feed are often more dominant.
  • Environment and husbandry: Whether a cat lives indoors or outdoors, whether it comes together with many other animals or is isolated – all this affects the bacterial diversity. Animals from animal shelters sometimes have a greater diversity than those in single households, presumably through contact with many germs. Stress and husbandry conditions also play a role: a stressed animal often has a shifted microbiome. A change of environment (moving, stay in animal boarding) can temporarily influence the intestinal flora and thus, for example, promote stress diarrhea.
  • Medications and antibiotics: Antibiotics are a double-edged sword – they fight pathogenic bacteria, but also damage the beneficial intestinal flora. Broad-spectrum antibiotics can completely change the microbial balance within a short time, decimate “good” bacteria and create space for resistant or opportunistic germs. A well-known example is an antibiotic-associated Clostridia overgrowth. Other medications also have an influence: proton pump inhibitors (acid-blocking medications) can adversely change the intestinal microbiome, presumably by changing the stomach pH and thereby other germ colonization in the intestine. Cortisone and immunosuppressants can act indirectly, as they downregulate the immune system in the intestine. Therefore, the following applies: use medications only when necessary and as specifically as possible and – if unavoidable – then support the intestinal flora in recovery, e.g. with probiotics.
  • Diseases: Acute diarrheal diseases themselves naturally change the microbiome – often they are accompanied by a decrease in beneficial lactobacilli and bifidobacteria and leave more space for e.g. Clostridia. Chronic intestinal inflammations (CE/IBD) are associated with sometimes significant dysbioses (e.g. less diversity, certain bacterial families reduced). However, it is often unclear whether the dysbiosis is the cause or the consequence of the disease. Systemic diseases can also have an effect: typical microbiome changes have been found in obesity (more Firmicutes bacteria, fewer Bacteroidetes bacteria), similar to humans. In the case of overweight, however, it is unclear whether the altered flora contributes to weight gain or is simply a consequence of the altered metabolic situation. Diabetes, liver diseases, etc. could also have repercussions on the intestinal flora, as metabolic products and digestive juice composition change.

In short, the cat’s intestinal microbiome is dynamic. A healthy, adult cat usually has a relatively stable microbiome that compensates for minor disturbances. However, major interventions such as antibiotic administration, radical feed changes or severe diseases can tip the balance.

Dysbiosis – when the Microbiome Gets out of Balance

Dysbiosis refers to an imbalance in the intestinal flora – the composition shifts in favor of potentially harmful germs, or the diversity decreases sharply. This can have a variety of consequences:

  • In cats with chronic enteropathies (IBD), a reduced bacterial diversity is often evident, e.g., a decrease in certain beneficial Clostridia groups. This dysbiosis could lead to inflammatory processes being favored, as the usual immunoregulatory signals from the good germs are missing. For example, fewer short-chain fatty acids were found in the intestines of diseased cats, which weakens the barrier and promotes Inflammatory conditions.
  • Dysbiosis itself can also maintain diarrhea. If the normal intestinal inhabitants are missing, opportunistic germs such as Clostridium perfringens can produce toxins unhindered, which disrupt intestinal movement and secretion. A vicious cycle: diarrhea causes dysbiosis, dysbiosis causes further diarrhea. Here, attempts are often made to counteract this with probiotics in order to restore the balance.
  • In cats treated with antibiotics, dysbiosis can lead to the intestine remaining sensitive after the medication is discontinued. For example, some cats develop chronically soft stools after repeated courses of antibiotics because the flora has not recovered and digestion is impaired.
  • Behavioral changes are also being discussed – e.g., whether dysbiosis has an influence on susceptibility to stress or eating behavior via the gut-brain axis. Although this has not been well researched in cats, it is known from other species that a disturbed intestinal flora can be linked to anxiety disorders or depression-like behavior.

Important to understand: A “disturbed” microbiome can be both a consequence of a disease (e.g., intestinal inflammation kills many bacteria) and a cause or contributing cause (e.g., outbreak of IBD due to previous dysbiosis). Research into this is ongoing, and much is still unclear. However, it is clear that restoring a healthy microbiome should often be part of the therapy, regardless of the cause or consequence – because a normal microbiome supports healing.

Diagnosis of dysbiosis: In routine practice, the microbiome is rarely analyzed directly, as this requires special laboratory methods (16S-rRNA sequencing etc.). However, there is a dysbiosis index test (developed mainly for dogs) that quantifies some bacterial groups and gives an indication of whether dysbiosis is present. This is still in its infancy in cats. Usually, the conclusion is drawn indirectly (e.g., no parasites, no bacteria isolated, does not respond to standard therapy → possibly dysbiosis/IBD).

Therapeutically, in case of suspected dysbiosis, the primary focus is on diet (highly digestible diet, possibly rich in prebiotics) and probiotics. This brings us to the next chapter: the targeted use of living beneficial microorganisms to promote intestinal health.

Probiotics in cats – benefits and scientific findings

According to the definition, probiotics are “living microorganisms that, when administered in sufficient quantities, confer a health benefit on the host”. In the context of cats, this usually refers to beneficial bacterial strains that are added via food or as a supplement to positively influence the intestinal microbiome. In this section, we explain what probiotics are, what effects they can have, what science says about them in cats, and how to use them in practice.

What are Probiotics and how Do They Work?

Probiotics for cats are often bacteria of the genera Lactobacillus, Bifidobacterium, Enterococcus or Streptococcus, which also occur naturally in the intestine. There are also yeast probiotics (e.g., Saccharomyces boulardii), which are mainly used for Diarrhea. Probiotic preparations are available on the market as powders, pastes or capsules and contain defined germ counts of the respective strains.

The mechanisms of action of probiotics in the intestine are diverse

  • They can shift the microbiome back into balance by introducing and promoting beneficial bacterial species. Some produce substances that inhibit pathogenic germs and compete with unwanted bacteria for space and nutrients.
  • Many probiotics positively stimulate the immune system in the intestine – e.g., they promote the formation of IgA (mucosal antibodies) and can induce anti-inflammatory cytokines. This strengthens the intestinal mucosa barrier and Inflammatory conditions can subside.
  • Probiotic bacteria improve stool consistency and quality. A balanced bacterial population ensures firmer, formed stools. Cats with dysbiosis often have mushy or smelly stools; probiotics can remedy this by normalizing the digestive processes.
  • Some studies suggest that probiotics can also have positive effects outside the intestine, e.g., on oral health (reduction of oral pathogenic germs) or the general immune defense against infections.

Important: Probiotic is not the same as probiotic. The effect is strain-specific. This means that even within the species Lactobacillus acidophilus, strain A can have different effects than strain B. Likewise, the dosage is decisive – enough living germs must arrive to achieve an effect. A good probiotic must therefore reach the intestine in sufficient quantity, survive the passage through the stomach and be able to assert itself for attachment in the intestine. Reputable preparations are tested accordingly to ensure that they meet these criteria (stable, safe, effective in sufficient doses).

Scientifically Proven Effects in Cats

Research into probiotics in veterinary medicine is catching up. While a lot of data is available for humans, some studies have also been carried out on cats in recent years. Here is an overview of scientific findings:

  • Reduction of diarrheal diseases: Several studies have shown that probiotics can reduce the duration and severity of Diarrhea in cats. In a placebo-controlled study with cats in an animal shelter, it was found that cats that received an Enterococcus faecium SF68 probiotic developed significantly less Diarrhea lasting for several days than untreated cats. Only 7.4% of the cats with probiotics had Diarrhea lasting longer, compared to 20.7% in the placebo group – a clear indication of the benefit of the probiotic. A more recent study with foster cats found that kittens that received a probiotic with Enterococcus hirae had a threefold reduced risk of developing Diarrhea compared to kittens without probiotics. This underlines the prophylactic potential, especially in stressful situations such as animal shelter/foster care.
  • Balance of the microbiome: Studies using DNA sequencing have shown that probiotics are able to influence the composition of the intestinal flora. For example, it was observed that after administration of certain lactobacilli, the relative number of potentially undesirable bacteria (such as Megamonas) decreased. A 2024 review summarizes that many studies confirm that probiotics improve the gastrointestinal functions of the cat and strengthen the immune system. In addition, benefits in other areas such as reduction of oral diseases or Overweight are mentioned, although these effects are partly still under research.
  • IBD and chronic enteropathies: Concrete studies on cats with IBD are still rare, but there are reports that the addition of probiotics can improve the clinical picture – similar to what is documented in dogs with chronic enteropathy. For example, a multistrain probiotic (probiotic with several strains) showed immunomodulatory effects in healthy cats, which could theoretically help with IBD. Studies are currently underway (e.g., at Colorado State University) on probiotics in the treatment of Feline IBD. However, the practical recommendation of many internists is already to undertake a therapeutic trial with probiotics in chronically intestinal cats, as there are successes and the risks are low.
  • Stress and immune system: An indirect effect of probiotics is the possible reduction of stress reactions. In other species, it has been shown that animals supported by probiotics get less Diarrhea under stress (e.g., during transport stress). It is also assumed in cats that probiotics can be given prophylactically in exciting situations (moving, new animals in the house etc.) to stabilize the intestinal flora and prevent stress-related soft stools.

Overall, the current study situation confirms that probiotics are safe and useful for cats, especially for the prevention and treatment of Diarrhea. Further effects (IBD therapy, general immune system boost) are suggested by many positive case reports and some studies, but partly still require further research. Nevertheless, more and more veterinarians are using probiotics as an accompanying therapy, as the possible benefit is great and the risk is small.

Practical Application of Probiotics

When using probiotics in cats, you should pay attention to a few points in order to achieve the best possible effect.

  • Selection of the product: There are numerous probiotics on the market. Ideal is a preparation that has been developed specifically for cats or at least tested in studies on cats. An example is Enterococcus faecium SF68, which is contained in commercial products (e.g. FortiFlora) and has been tested on cats. Mixtures of Lactobacillus and Bifidobacteria strains, as they are often used for dogs, can also be suitable for cats, but you should pay attention to the dosage. Yeast probiotics (Saccharomyces) are often recommended for Diarrhea treatment, as they multiply quickly and can bind toxins – these can be particularly helpful in antibiotic-associated Diarrhea, as yeasts are not killed by antibiotics.
  • Dosage and duration: Probiotics should be given in sufficient quantity. Usually, they are administered once a day, often in the order of several billion colony-forming units (CFU) per dose (note manufacturer’s instructions). An underdose brings little. The duration depends on the area of application: In acute Diarrhea, they are given until the stool is normal (often a few days to 2 weeks). In chronic problems or as prevention, they can also be given long-term. Long-term administration is considered harmless, provided that the product is of high quality.
  • Administration: Many probiotic products come as a tasty powder that is sprinkled over the food. Most cats accept this well, as some have a liver or chicken base as a flavor carrier. If the cat is picky, you can mix the powder with some favorite wet food. Important: Do not mix hot water or very warm food with probiotics, as the heat can kill the bacteria. Room temperature is ideal. If a cat takes absolutely nothing, there is also paste in applicators or you can enter capsules.
  • Combination with other therapies: Probiotics can be combined well with other treatments. Especially after or during antibiotic administration, it makes sense to give probiotics (e.g. time-delayed to the antibiotic, so that not everything is killed off again immediately) to prevent dysbiosis. In case of food changes or stressful events, you can feed probiotics in advance and during to stabilize the flora. In chronic cases such as IBD, probiotics are usually administered in addition to diet and medication as a fourth pillar, so to speak.
  • Monitoring the success: As with all treatments, you should also observe the course with probiotics. Does the stool become firmer? Does the smell decrease? Is the cat Vomiting less? Some effects show up within a few days (Diarrhea often improves quickly), others take longer (e.g. influence on skin/coat or weight). If a probiotic shows no effect, you can also try a different strain – perhaps the cat responds better to a different mix.

Safety and Limits of Probiotics

  • Probiotics are considered very safe. Since they are natural intestinal inhabitants, the risk of side effects is low. In rare cases, it can initially lead to somewhat softer stools or Flatulence, which is predominantly mild and temporary. It is important to choose high-quality products to exclude contamination with unwanted germs.
  • Probiotics have limits where severe structural problems exist: An Intestinal obstruction does not resolve with probiotics, a severe viral infection requires more intensive measures. They are not a panacea, but a valuable support. In addition, they do not always work immediately – if, for example, there is hardly any normal mucous membrane left (in severe IBD), medication is often also needed to create an environment in which probiotics can adhere again.
  • Another practical point: Probiotics must be stored refrigerated or at least dry (depending on the manufacturer). Heat can reduce the effectiveness, so they should not be stored in the sun or in a hot car.

In conclusion, probiotics have taken an important place in the modern care of cats with gastrointestinal problems. Many veterinarians now consider them “part of the toolbox” to maintain or restore intestinal health – scientifically substantiated and proven in practice.

Frequently Asked Questions (FAQs)

  • Question:
    Why are cats so susceptible to gastrointestinal problems?

    Answer:
    Cats have a very sensitive digestive tract and often react to even small changes (e.g. new food type, stress, parasite infestation) with Vomiting or Diarrhea. Since they are true creatures of habit by nature and are often only used to little variety in their food, even an abrupt change of food can lead to complaints. Their very short intestine and the high sensitivity to certain additives or bacteria also favor gastrointestinal problems.

  • Question:
    How do I recognize that my cat may be suffering from Inflammatory conditions (IBD)?

    Answer:
    A chronic, recurring digestive disorder with changing symptoms such as Diarrhea, Vomiting and possibly Weight loss may indicate “Inflammatory Bowel Disease” (IBD). Some cats even retain their appetite, but still lose weight. An exact diagnosis is only possible by excluding other causes (e.g. parasites, food allergies) and usually endoscopy with biopsy.

  • Question:
    How can I prevent my cat from getting gastrointestinal problems in the first place?

    Answer:
    A high-quality, species-appropriate diet with slow food change, regular deworming and vaccinations (especially against feline panleukopenia) as well as a low-stress environment are the most important pillars. Fresh water, clean bowls and a well-maintained litter box also help to avoid infections and stress. In long-haired cats, regular coat care is useful to reduce hairball formation.

  • Question:
    What can I do if my cat suddenly Vomiting severely or has Diarrhea?

    Answer:
    First, you should observe whether further symptoms (e.g. Apathy, Fever, blood in the vomit or stool) are added. In case of single mild Vomiting or Diarrhea, a short food break for a few hours can help to relieve the gastrointestinal tract. If the symptoms remain or become stronger, you should immediately consult a veterinarian so that no dehydration or serious cause is overlooked.

  • Question:
    Can home remedies or probiotics help with gastrointestinal complaints?

    Answer:
    In mild cases, home remedies such as a bland diet (boiled chicken, some rice) can provide relief. Probiotics support the development of a healthy intestinal flora through their positive bacterial strains. They are particularly helpful after antibiotic use or during stressful phases. However, they do not replace veterinary clarification if acute or severe symptoms exist.

  • Question:
    What role does the intestinal microbiome play in gastrointestinal problems?

    Answer:
    The gut microbiome is a community of countless microorganisms, most of which are beneficial and support digestion and the immune system. If this microbiome becomes unbalanced due to factors such as infections, poor diet, or medication, it can lead to digestive problems (e.g., chronic Diarrhea) and an increased susceptibility to infections. Therefore, a balanced diet and – if necessary – probiotics are important building blocks for a healthy gut environment.

  • Question:
    When should I definitely take my cat to the vet?

    Answer:
    At the latest, you should go to the vet if the Vomiting or Diarrhea lasts longer than 24 hours, blood is visible in the vomit or stool, or the animal becomes apathetic. Likewise, if the animal no longer drinks water or shows signs of dehydration (dry mucous membranes, sunken eyes). Especially in young, old, or weakened cats, quick action is important, as they can quickly become life-threateningly dehydrated.

  • Question:
    Can an incorrect food composition be the cause of chronic gastrointestinal problems?

    Answer:
    Yes, often inferior or unsuitable food for cats (e.g., high grain content, too much fat, incompatible proteins) contributes to persistent digestive problems. Also, suddenly changing the food often triggers Diarrhea or Vomiting. A consistent and well-monitored exclusion diet can clarify whether and which food is causing the problems, so that it can be avoided in the future or switched to a special diet.

Literature

WICHERT, Brigitta. Pre- and Probiotics – When their use is useful in dogs and cats. kleintier konkret, 2017, 20th year, No. 06, pp. 2-10.

KRÖGER, Susan. Probiotics and prebiotics for dogs and cats – what can they do?. team. konkret , 2023, 19th year, No. 01, pp. 13-16.

https://www.purina.de/artikel/katzen/fuettern/tipps/probiotika-fuer-katzen