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Draining fistula with purulent discharge in Dogs

Author: Dr. med. vet. Gisa Löwe | Last modified: 17.02.2026

When to visit the vet?

Urgent see a veterinarian within 24 hours

RED for Fever, severe lethargy, rapid spread, significant Pain, foul odor, proximity to eye/throat/anus with dysfunction, or signs of circulatory issues (suspected sepsis).

Unsure about what’s wrong with your pet? Feel free to use our Symptom Checker for more clarity

Definition

A fistulaA fistula is an unnatural channel or connection between two organs, or between an organ and the body’s surface, that can arise from disease, injury, or surgical procedures. In dogs and cats, fistulas can be a cause for concern and may require treatment. is an unnatural passage that forms between an internal organ and the body surface, or between two internal organs. In dogs, a draining fistulaA fistula is an unnatural channel or connection between two organs, or between an organ and the body’s surface, that can arise from disease, injury, or surgical procedures. In dogs and cats, fistulas can be a cause for concern and may require treatment. with purulentPurulent refers to pus or the production of pus, which may indicate a bacterial infection. Purulent inflammatory conditions are often painful and may have significant swelling and redness. discharge can occur, indicating an infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease. or inflammatory condition.

Can Occur with the Following Diseases:

Basics and possible causes

Fistulas in dogs often arise as a result of persistentPersistent means lasting or continuing for an extended period. In veterinary medicine, it can refer to chronic diseases or symptoms that do not subside. inflammatory conditions or infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease.. The body forms this channel to drain infected or inflamed material. The purulentPurulent refers to pus or the production of pus, which may indicate a bacterial infection. Purulent inflammatory conditions are often painful and may have significant swelling and redness. discharge indicates that bacteriaBacteria are microscopic, single-celled organisms that exist in almost every environment on Earth. Some types of bacteria are beneficial or even essential to life, while others can cause disease. have accumulated in the fistulaA fistula is an unnatural channel or connection between two organs, or between an organ and the body's surface, that can arise from disease, injury, or surgical procedures. In dogs and cats, fistulas can be a cause for concern and may require treatment., triggering an immune responseAn immune response is the immune system's reaction to foreign substances (antigens), such as microorganisms or proteins. It involves a series of processes aimed at recognizing, fighting, and eliminating these antigens. from the body.

Common causes of fistulas in dogs include bacterial infections, traumatic injuries, foreign bodies, or chronicChronic refers to a condition or disease that is long-lasting or permanent. Chronic diseases often develop slowly and can lead to persistent or recurring health problems over time. diseases such as anal gland disease. Autoimmune diseasesAutoimmune diseases are conditions in which the immune system mistakenly attacks the body's own cells or tissues as if they were foreign substances. Examples in dogs and cats include autoimmune hemolytic anemia and systemic lupus erythematosus. can also lead to the formation of fistulas by weakening tissue and promoting inflammatory processes.

Another triggerA trigger is a stimulus that elicits a specific reaction or state. In veterinary medicine, this can refer to emotional responses, such as fear or aggression, or medical conditions, such as seizures in dogs and cats. can be skin diseases where pores become clogged and infected. These infections can spread and lead to fistulaA fistula is an unnatural channel or connection between two organs, or between an organ and the body's surface, that can arise from disease, injury, or surgical procedures. In dogs and cats, fistulas can be a cause for concern and may require treatment. tracts. Breeds with deep skin folds or dense fur have an increased risk for such skin problems.

In rare cases, fistulas can also be caused by parasites that burrow into the skin and cause inflammatory conditions. Furthermore, surgery or a surgical procedure can lead to fistulaA fistula is an unnatural channel or connection between two organs, or between an organ and the body's surface, that can arise from disease, injury, or surgical procedures. In dogs and cats, fistulas can be a cause for concern and may require treatment. formation if healing does not proceed optimally.

Typical accompanying symptoms

Local swelling: A visible or palpable swelling near the fistulaA fistula is an unnatural channel or connection between two organs, or between an organ and the body's surface, that can arise from disease, injury, or surgical procedures. In dogs and cats, fistulas can be a cause for concern and may require treatment. may occur, which is often painful.
Redness and warmth: The surrounding skin may be red and warm, indicating an inflammatory condition.
Unpleasant odor: The pus draining from the fistulaA fistula is an unnatural channel or connection between two organs, or between an organ and the body's surface, that can arise from disease, injury, or surgical procedures. In dogs and cats, fistulas can be a cause for concern and may require treatment. can have an unpleasant odor, indicating a bacterial infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease..
Itching or Scratching: The dog may repeatedly scratch or lick the affected area, indicating discomfort or itching.
General discomfort: The dog may show signs of discomfort, such as loss of appetite, lethargy, or altered behavior.
Fever: In some cases, the dog may develop Fever if the infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease. becomes systemic.

When to see a vet?

A veterinarian should be consulted if the dog shows symptoms indicative of fistulaA fistula is an unnatural channel or connection between two organs, or between an organ and the body's surface, that can arise from disease, injury, or surgical procedures. In dogs and cats, fistulas can be a cause for concern and may require treatment. formation, especially if accompanied by purulentPurulent refers to pus or the production of pus, which may indicate a bacterial infection. Purulent inflammatory conditions are often painful and may have significant swelling and redness. discharge. Veterinary advice is also required if the dog’s condition worsens or new symptoms appear.

An immediate visit to the veterinarian is necessary if the dog shows signs of severe Pain, if its general condition rapidly deteriorates, or if Fever occurs. These signs indicate that the infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease. may be spreading or that a more serious underlying disease is present.

Symptom recognition for the pet owner and veterinary diagnostic procedure

Pet owners should look for signs of fistulas, such as Swelling, redness, or pus discharge. A thorough inspection of the dog’s coat and skin can help detect unusual changes. If a fistulaA fistula is an unnatural channel or connection between two organs, or between an organ and the body's surface, that can arise from disease, injury, or surgical procedures. In dogs and cats, fistulas can be a cause for concern and may require treatment. is suspected, it is advisable not to manipulate the affected area to avoid worsening the condition.

The veterinarian will perform a physical examination and consider the dog’s medical historyThe medical history is the systematic collection of a patient's medical history through questioning. It includes information about previous illnesses, treatments, allergies, and lifestyle habits.. Imaging techniques such as ultrasoundUltrasound refers to sound waves that are above the hearing threshold of the human ear. In medicine, ultrasound is used for diagnostic imaging procedures to visualize internal organs, tissues, and blood flow. or X-rayX-ray is an imaging technique that uses X-rays to create images of the inside of the body. It is often used to diagnose bone fractures, lung diseases, and other conditions. may be necessary to determine the extent of the fistulaA fistula is an unnatural channel or connection between two organs, or between an organ and the body's surface, that can arise from disease, injury, or surgical procedures. In dogs and cats, fistulas can be a cause for concern and may require treatment.. A sample of the pus can be taken to identify the specific bacteriaBacteria are microscopic, single-celled organisms that exist in almost every environment on Earth. Some types of bacteria are beneficial or even essential to life, while others can cause disease. and plan appropriate antibiotic therapyTherapy refers to the treatment of diseases or disorders with the aim of alleviating symptoms, promoting healing, or improving quality of life. Therapies can be medicinal, surgical, or through other medical interventions..

In some cases, an endoscopic examination or a biopsyA biopsy is a medical procedure in which a small amount of tissue is removed from the body to be examined under a microscope for signs of disease. Biopsies can help diagnose cancer and other conditions. is performed to determine the cause of fistulaA fistula is an unnatural channel or connection between two organs, or between an organ and the body's surface, that can arise from disease, injury, or surgical procedures. In dogs and cats, fistulas can be a cause for concern and may require treatment. formation and rule out other serious diseases. These diagnostic procedures help develop targeted treatment.

What the pet owner can do and professional therapy options

Until the veterinary visit, the pet owner should ensure that the dog does not scratch or lick the affected area to avoid worsening the infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease.. A protective collar can help prevent access to the fistulaA fistula is an unnatural channel or connection between two organs, or between an organ and the body's surface, that can arise from disease, injury, or surgical procedures. In dogs and cats, fistulas can be a cause for concern and may require treatment..

It is important to keep the affected area clean. The pet owner can gently clean the region with a mild antiseptic to reduce the bacterial load. However, aggressive cleaning agents should be avoided as they could further irritate the tissue.

The pet owner should ensure that the dog gets enough rest and is not exposed to stressStress refers to the state of an organism reacting to external stimuli or demands. In veterinary medicine, stress can have physical or psychological effects on animals, impacting their health and well-being. situations, as stressStress refers to the state of an organism reacting to external stimuli or demands. In veterinary medicine, stress can have physical or psychological effects on animals, impacting their health and well-being. can weaken the immune systemThe immune system is the body's defense system against infectious agents such as bacteria, viruses, fungi, and parasites. It comprises a complex network of organs, cells, and molecules that work together to protect the body. and delay healing. A balanced diet can also help strengthen the immune systemThe immune system is the body's defense system against infectious agents such as bacteria, viruses, fungi, and parasites. It comprises a complex network of organs, cells, and molecules that work together to protect the body..

If the dog shows Pain, the pet owner should discuss appropriate pain relievers with the veterinarian. Self-medication with human pain relievers must be strictly avoided, as these can be harmful to dogs.

Outlook on current research

Current research on draining fistulaA fistula is an unnatural channel or connection between two organs, or between an organ and the body's surface, that can arise from disease, injury, or surgical procedures. In dogs and cats, fistulas can be a cause for concern and may require treatment. with purulentPurulent refers to pus or the production of pus, which may indicate a bacterial infection. Purulent inflammatory conditions are often painful and may have significant swelling and redness. discharge in dogs focuses on identifying the underlying mechanisms that lead to this symptom. Scientists are investigating how chronicChronic refers to a condition or disease that is long-lasting or permanent. Chronic diseases often develop slowly and can lead to persistent or recurring health problems over time. inflammatory processes and infections lead to the formation of fistulas. These studies aim to better understand the role of the immune systemThe immune system is the body's defense system against infectious agents such as bacteria, viruses, fungi, and parasites. It comprises a complex network of organs, cells, and molecules that work together to protect the body. and specific bacteriaBacteria are microscopic, single-celled organisms that exist in almost every environment on Earth. Some types of bacteria are beneficial or even essential to life, while others can cause disease. in the development of fistulas. Researchers use advanced molecular techniques to identify the genetic and microbial factors that increase the risk of fistulaA fistula is an unnatural channel or connection between two organs, or between an organ and the body's surface, that can arise from disease, injury, or surgical procedures. In dogs and cats, fistulas can be a cause for concern and may require treatment. formation.

Another research focus is the development of new therapeutic approaches for treating fistulas and reducing the associated purulentPurulent refers to pus or the production of pus, which may indicate a bacterial infection. Purulent inflammatory conditions are often painful and may have significant swelling and redness. discharge. Current studies are investigating the effectiveness of antibiotics and anti-inflammatory medications in the treatment of fistulas in dogs. In addition, there is promising research on the application of biological therapies, such as the use of stem cells, to promote fistulaA fistula is an unnatural channel or connection between two organs, or between an organ and the body's surface, that can arise from disease, injury, or surgical procedures. In dogs and cats, fistulas can be a cause for concern and may require treatment. healing and modulate the dog’s immune systemThe immune system is the body's defense system against infectious agents such as bacteria, viruses, fungi, and parasites. It comprises a complex network of organs, cells, and molecules that work together to protect the body..

In addition to medical treatment, research is being conducted on how dietary interventions and lifestyle changes can influence the risk and severity of draining fistulaA fistula is an unnatural channel or connection between two organs, or between an organ and the body's surface, that can arise from disease, injury, or surgical procedures. In dogs and cats, fistulas can be a cause for concern and may require treatment. with purulentPurulent refers to pus or the production of pus, which may indicate a bacterial infection. Purulent inflammatory conditions are often painful and may have significant swelling and redness. discharge. Studies show that a balanced diet rich in omega-3 fatty acids has anti-inflammatory properties and may help reduce inflammatory conditions and fistulaA fistula is an unnatural channel or connection between two organs, or between an organ and the body's surface, that can arise from disease, injury, or surgical procedures. In dogs and cats, fistulas can be a cause for concern and may require treatment. formation. Researchers are also investigating whether regular exercise and stressStress refers to the state of an organism reacting to external stimuli or demands. In veterinary medicine, stress can have physical or psychological effects on animals, impacting their health and well-being. management techniques can have a positive impact on the immune systemThe immune system is the body's defense system against infectious agents such as bacteria, viruses, fungi, and parasites. It comprises a complex network of organs, cells, and molecules that work together to protect the body. and the dog’s overall health.

Research has also made progress in developing diagnostic techniques to detect and better monitor fistulaA fistula is an unnatural channel or connection between two organs, or between an organ and the body's surface, that can arise from disease, injury, or surgical procedures. In dogs and cats, fistulas can be a cause for concern and may require treatment. formation early. Imaging techniques, such as ultrasoundUltrasound refers to sound waves that are above the hearing threshold of the human ear. In medicine, ultrasound is used for diagnostic imaging procedures to visualize internal organs, tissues, and blood flow. and MRI, are increasingly used to visualize fistulas and the surrounding tissues in detail. These technologies help veterinarians determine the exact location and extent of the fistulas, which is crucial for planning an effective treatment strategy.

Frequently asked questions

1. What is a fistula in dogs?

A fistula is an unnatural channel that can form between two body cavities or from a body cavity to the body surface. In dogs, fistulas often occur as a result of infections, inflammatory conditions, or injuries and can discharge pus.

2. How do I know if my dog has a fistula?

A common sign of a fistula is a small opening on the skin surface from which pus drains. Other symptoms may include redness, Swelling, and discomfort in the affected region. If you notice such symptoms, you should see a veterinarian.

3. What causes pus in a fistula?

Pus in a fistula is usually caused by a bacterial infection. The dog's immune system reacts to the infection by producing pus, which consists of dead white blood cells, bacteria, and tissue debris.

4. How is a fistula in dogs treated?

The treatment of fistulas can include medications such as antibiotics and anti-inflammatory agents. In some cases, surgical intervention may be required to clean and close the fistula. The exact treatment depends on the cause and extent of the fistula.

5. Can a fistula heal on its own?

In rare cases, a small fistula may heal on its own, especially if the underlying cause is treated. More often, however, fistulas require medical treatment to prevent infections and complications.

6. Why is my dog susceptible to fistula formation?

Some dogs are genetically predisposed to fistula formation, while others are susceptible due to factors such as repeated infections, injuries, or chronic inflammatory conditions. Certain breeds may have a higher risk.

7. Can fistulas in dogs lead to complications?

Yes, untreated fistulas can lead to serious complications, including chronic infections, tissue damage, and in rare cases, sepsis. Early diagnosis and treatment are crucial to avoid complications.

8. How can I prevent fistula formation in my dog?

Regular veterinary check-ups, a balanced diet, and good hygiene can help reduce the risk of fistula formation. It is also important to treat injuries and infections early to prevent the formation of fistulas.

9. Is fistula formation in dogs painful?

Yes, fistulas can be painful, especially when associated with an infection. Dogs may show signs of discomfort, such as Licking or biting the affected area. Pain management is an important part of the treatment.

10. Should I bathe my dog with a fistula?

It is important to maintain hygiene around the fistula, but bathing should be done with caution to avoid further irritation. Your veterinarian can provide specific instructions on how the affected area should be cleaned.