Renal Adenocarcinoma (Kidney Cancer) in Dogs
- Occurrence: rarer
- Location of illness: Abdomen/pelvis
Renal adenocarcinoma, also known as kidney cancer, is a malignant neoplasm that develops from the glandular epithelial cells of the renal parenchyma. This form of tumor belongs to the group of primary kidney Tumors and accounts for approximately 60–85% of all malignant renal neoplasms in dogs. Histologically, adenocarcinoma is characterized by atypical epithelial cells that form gland-like structures and exhibit an invasive growth pattern.
The most important facts at a glance
Renal adenocarcinoma in dogs is a rare but aggressive tumor disease that predominantly affects older animals. The etiology is multifactorial, with genetic and environmental influences. Clinically, the disease often presents only in advanced stages with non-specific symptoms such as weight loss, lethargy, and hematuria, which makes early detection difficult.
Diagnosis requires a multimodal approach consisting of clinical examination, laboratory diagnostics, imaging, and histopathological evaluation. Comprehensive staging is essential for therapy planning and prognosis assessment. Surgical removal of the tumor by nephrectomy remains the most important therapy option for localized tumors, while adjuvant treatments such as chemotherapy or targeted therapies can be considered for advanced disease.
The prognosis varies considerably depending on the tumor stage, histological grade, and success of surgical resection. Structured follow-up care with regular clinical, laboratory diagnostic, and imaging examinations is essential to detect recurrences early and monitor kidney function. Supportive measures, especially an adapted diet, contribute significantly to maintaining the quality of life.
Despite advances in diagnostics and therapy, renal adenocarcinoma remains a challenge in veterinary oncology. The exploration of new molecular markers and innovative therapeutic approaches, inspired by findings from human medicine, offers hope for improved treatment outcomes in the future.
Causes
Compared to other cancers in dogs, kidney tumors are relatively rare, with an incidence (frequency) of less than 2% of all canine neoplasms. Nevertheless, they pose a particular challenge due to their aggressive nature and often late diagnosis. Renal adenocarcinoma can occur unilaterally or bilaterally, with unilateral involvement being more common. The disease predominantly affects older dogs with an average age of onset of 8 to 9 years, although dogs of any age can be affected.
Noteworthy is the similarity between canine kidney cancer and renal cell carcinoma in humans, which makes this disease interesting for comparative oncological research. Both types of tumors show similar molecular signaling pathways and changes, making dogs a valuable model for researching new therapeutic approaches.
- Genetic Predisposition: Current studies suggest that certain dogs may have a genetic predisposition to renal adenocarcinomas. Mutations in oncogenic signaling pathways (e.g., in genes such as VHL or HIF) play a role, analogous to findings in human medicine.
- Environmental Factors: Exposure to certain chemicals or chronic kidney diseases can promote the development of a kidney tumor.
Breed Aspects: Even if no clear accumulation is known, a higher incidence is occasionally reported in some larger breeds such as the German Shepherd, Golden Retriever, or Bernese Mountain Dog.
The exact etiology of renal adenocarcinoma in dogs is multifactorial and not yet fully understood. Current research indicates a complex interplay of genetic and environmental factors:
Genetic predisposition plays a crucial role in the development of kidney cancer. Recent molecular genetic studies have shown that mutations in tumor suppressor genes such as VHL (von Hippel-Lindau) and oncogenes such as MET, similar to humans, can contribute to tumor development. These genetic changes lead to a dysregulation of cellular signaling pathways, especially the HIF (hypoxia-inducible factor) pathway, resulting in uncontrolled cell growth and increased angiogenesis.
Chronic kidney diseases can increase the risk of developing renal adenocarcinoma. Prolonged inflammatory processes and repeated tissue damage can lead to DNA damage and promote malignant transformation. Likewise, nephrotoxic substances such as certain heavy metals, pesticides, or medications can damage the kidney tissue and contribute to cancer development in the long term.
Although no clear breed predisposition has been demonstrated, a certain accumulation is observed in medium to large dog breeds such as German Shepherds, Golden Retrievers, Labrador Retrievers, and Bernese Mountain Dogs. This could indicate breed-specific genetic factors that increase susceptibility to kidney tumors.
Hormonal factors are also discussed, as some studies have found a higher incidence in male dogs, which could indicate a possible influence of sex hormones. However, the data on this are not yet conclusive.
Symptoms
The clinical manifestations of renal adenocarcinoma in dogs are often non-specific and develop insidiously, which makes early detection difficult. The symptoms can vary depending on the tumor stage, size, and degree of metastasis:
In early stages, the disease is often asymptomatic, as the healthy kidney can compensate for the function. However, as the tumor grows, signs of illness may increasingly appear. The most common symptoms include lethargy, reduced appetite to anorexia, and progressive Weight loss. These non-specific signs are often initially attributed to the age of the animal, which can lead to delays in diagnosis.
Hematuria (Blut im Urin) is a characteristic symptom in about 20–40% of affected dogs and results from the invasion of the tumor into the renal pelvis or the draining urinary tract. The blood admixtures can occur intermittently and be macroscopically visible or only microscopically detectable. In advanced cases, flank Pain may occur, which is expressed by Sensitivity to touch in the kidney area or Behavioral changes such as unwillingness to move.
In larger Tumors, a palpable (feelable) increase in circumference can be detected in the cranial abdomen. In about 30% of cases, affected dogs develop secondary arterial hypertension, which can lead to further clinical manifestations such as retinal Bleeding or neurological symptoms. Paraneoplastic syndromes such as hypercalcemia, polycythemia, or Fever of unknown origin can also occur and are due to the production of bioactive substances by the tumor.
In advanced disease with metastasis, additional organ-specific symptoms may occur, especially Cough, dyspnea, or exercise intolerance in pulmonary metastases, or neurological deficits in bone metastases. Approximately 50% of dogs already show signs of metastasis at initial presentation, most commonly in the lungs, regional lymph nodes, liver, and bones.
Diagnosis
- Imaging techniques such as ultrasound, X-rays, or CT scans to identify Tumors in the kidneys
- Biopsy of the tumor to confirm the diagnosis and assess the tumor grade
- Laboratory tests to check kidney function and the general condition of the dog
The diagnosis of renal adenocarcinoma in dogs requires a systematic approach with various, complementary examination methods. An early and precise diagnosis is crucial for therapy planning and prognosis assessment.
The clinical examination is the starting point of the diagnostics. Palpation of the abdomen may reveal an enlarged, firm, or painful kidney. Auscultation of the thorax can provide indications of pulmonary metastases. Laboratory tests include a complete blood count, serum biochemistry, and urinalysis. Typical findings may include normochromic, normocytic anemia, leukocytosis, elevated kidney parameters (urea, creatinine) in advanced disease, and Hematuria in the urine sediment. In some patients, elevated calcium levels may also occur as a paraneoplastic phenomenon.
Imaging plays a central role in diagnostics. Abdominal ultrasound is usually the first imaging method and can show changes in size, shape, and echotexture of the kidney. Typically, renal adenocarcinomas appear as heterogeneous, often hyperechoic masses with irregular margins and possible cystic or necrotic areas. Doppler sonography can also provide information about the vascularization of the tumor and possible invasion into the renal vessels or the vena cava caudalis.
For comprehensive staging, further imaging procedures such as chest X-rays (for metastasis search), computed tomography (CT), or magnetic resonance imaging (MRI) are essential. These modalities allow a more precise assessment of the local tumor extension, vascular invasion, and potential metastases. In particular, contrast-enhanced CT has proven valuable for preoperative planning and staging.
The definitive diagnosis requires a histopathological examination. This can be done by fine needle aspiration, a Tru-Cut biopsy, or after surgical removal of the tumor. Fine needle aspiration is minimally invasive but often provides only limited diagnostic information and carries the risk of tumor seeding. The Tru-Cut biopsy offers more tissue for histological assessment but is more invasive and associated with similar risks. The histopathological examination after nephrectomy provides the most comprehensive information about tumor type, grade, and invasiveness.
Molecular diagnostics is gaining increasing importance. Immunohistochemical examinations can detect specific tumor markers such as cytokeratin, vimentin, or CD10 and contribute to a more accurate classification. Genetic analyses can identify prognostically relevant mutations and identify potential targets for targeted therapies.
Therapy
- Surgical Removal: A nephrectomy (removal of the affected kidney) is often the first choice, provided the second kidney is functional and the tumor has not yet formed distant metastases.
- Chemotherapy: Certain protocols (e.g., based on doxorubicin) are used depending on the tumor stage. The effectiveness is still the subject of current studies.
- Targeted Therapies (Targeted Therapy): Based on advances in human medicine, inhibitors of signaling pathways (tyrosine kinase inhibitors) are being researched.
- Immunotherapy: Initial approaches in which immune checkpoint inhibitors are tested show potential but need further evaluation.
Supportive therapies to relieve Pain and improve quality of life.
The treatment of renal adenocarcinoma in dogs is based on a multimodal approach, with surgical intervention still being the most important pillar. The therapy decision must be made individually, taking into account the tumor stage, the general condition of the patient, and the available technical options.
A surgical removal of the tumor by radical nephrectomy is the therapy of choice for localized, non-metastatic tumors. Here, the affected kidney is removed together with the surrounding fat capsule, the proximal ureter, and the regional lymph nodes. For very large tumors or suspected vascular invasion, an extended approach may be necessary. The operation should be performed by an experienced surgeon, as intraoperative complications such as severe Bleeding can occur due to the rich vascularization of the kidney. A prerequisite for nephrectomy is sufficient functionality of the contralateral kidney, which should be ensured preoperatively by means of laboratory tests and imaging procedures.
In selected cases with small, well-defined tumors, a partial nephrectomy (kidney-preserving surgery) can be considered. This technique is technically more demanding but can be advantageous in bilateral tumors or in patients with impaired kidney function. Newer minimally invasive techniques such as laparoscopic nephrectomy are becoming increasingly important and can contribute to faster postoperative recovery.
Adjuvant chemotherapy is controversially discussed, as its effectiveness in canine renal adenocarcinoma has not been clearly proven. However, it can be considered in patients with a high risk of metastasis, incomplete tumor resection, or pre-existing metastases. Protocols based on doxorubicin, carboplatin, or mitoxantrone are most commonly used, with response rates being variable. A combination of different chemotherapeutic agents may be beneficial in some cases.
Targeted therapies, especially tyrosine kinase inhibitors such as Toceranib (Palladia®) or Masitinib, represent a promising option. These drugs inhibit specific signaling pathways that are important for tumor growth and angiogenesis. Studies have shown that they can lead to stabilization of the disease in some dogs with advanced kidney cancer. The identification of predictive biomarkers could enable better patient selection for this form of therapy in the future.
Immunotherapy with checkpoint inhibitors is still in the experimental stage but shows promising results in preclinical studies. These drugs reactivate the body’s own immune system to recognize and fight tumor cells. Initial clinical trials with antibodies against PD-1/PD-L1 in dogs with various types of tumors, including renal carcinomas, are currently underway.
Supportive measures are an essential component of the treatment concept. These include an adapted diet (kidney-friendly diet in case of impaired kidney function), adequate pain therapy, and the treatment of concomitant diseases. In patients with advanced disease, palliative care is the focus, with the aim of maintaining the quality of life for as long as possible.
Prognosis and follow-up care
The prognosis depends on the stage of the disease, the size and location of the tumor, and the response to treatment. Tumors diagnosed and treated early usually have a better prognosis. However, kidney cancer is often diagnosed only in an advanced stage, which complicates treatment and prognosis. In such cases, treatment focuses on slowing the progression of the disease and maintaining the dog’s quality of life for as long as possible. The survival rate varies greatly depending on the individual case, and follow-up care is important to detect and treat relapses or metastases early.
Aftercare
- Regular Check-ups: Blood and urine tests, imaging procedures (X-rays, ultrasound) at intervals of 3 to 6 months.
- Nutrition and Management: A dietary adjustment (kidney-friendly feeding) can help support the function of the remaining kidney.
- Quality of Life: Special attention to possible symptoms of kidney weakness (e.g., increased thirst, weight loss) and early therapeutic interventions contribute to an improved quality of life.
The prognosis for dogs with renal adenocarcinoma varies considerably and depends on several factors, including tumor stage at diagnosis, histological grade, presence of metastases, and success of surgical resection. Careful follow-up is essential to detect recurrences early and optimize quality of life.
In dogs with localized tumors that could be completely surgically removed, the median survival time is between 12 and 24 months. Factors associated with a more favorable prognosis include a low histological malignancy grade, the absence of vascular invasion, and negative resection margins. In contrast, patients with advanced disease, especially in the presence of distant metastases, have a significantly poorer prognosis with median survival times of 3 to 6 months despite multimodal therapy.
The histological subtype of adenocarcinoma can have prognostic relevance. Papillary and tubular variants tend to show a less aggressive behavior than solid or sarcomatoid subtypes. Molecular markers such as the expression of VEGF (Vascular Endothelial Growth Factor), Ki-67, or p53 are increasingly being investigated as potential prognostic indicators.
A structured follow-up program is essential for all patients after treatment of renal adenocarcinoma. In the first six months after the operation, monthly check-ups are recommended; after that, the intervals can be extended to three to six months if the course is stable. Each follow-up examination should include a thorough clinical examination, blood and urine analyses, and imaging procedures.
Monitoring kidney function is particularly important, as the remaining kidney must take over the entire excretory function. Regular determinations of urea, creatinine, electrolytes, and urine-specific gravity can reveal early signs of kidney dysfunction. Blood pressure measurement should also be part of routine monitoring, as hypertension is a common complication.
Imaging procedures for metastasis search include thoracic radiographs every three months in the first year and abdominal ultrasound examinations to assess the contralateral kidney and possible local recurrences. In case of suspected metastases or in high-risk patients, further examinations such as CT or MRI may be indicated.
Nutritional counseling is an important aspect of follow-up care. An individually adapted diet can support the function of the remaining kidney and improve the quality of life. In case of impaired kidney function, a phosphorus- and protein-reduced diet is recommended, supplemented by an adequate fluid intake.
If there are signs of a recurrence or metastasis, the therapy options must be re-evaluated. In some cases, local treatment procedures such as radiation therapy for isolated metastases or systemic therapies such as chemotherapy or targeted drugs can be considered. Palliative care with a focus on pain management and maintaining quality of life is becoming increasingly important in advanced stages.
Prevention
Renal adenocarcinoma cannot be reliably prevented, as the causes are often unclear. Nevertheless, preventive measures can support kidney health and facilitate early diagnosis. Regular check-ups, especially in older dogs, should include blood and urine analyses. A balanced diet, adequate water intake, and avoidance of kidney toxins (e.g., certain medications, poisonous plants) are important. X-ray or ultrasound checks can help to detect changes early in at-risk patients. Owners should pay attention to symptoms such as weight loss, blood in the urine, or increased drinking and have them clarified by a veterinarian immediately.
Outlook on current research
Research on renal adenocarcinoma in dogs is constantly evolving, with several promising directions being pursued. The One Health approach, which uses the parallels between human and canine tumors, is gaining in importance and promotes the transfer of knowledge between human and veterinary medicine.
In the field of molecular oncology, genetic and epigenetic changes underlying canine renal adenocarcinoma are being intensively researched. Next-generation sequencing technologies enable the identification of driver mutations and molecular signatures that could serve as prognostic markers or therapeutic targets. Comparative genomic studies have already shown remarkable similarities between canine and human renal cell carcinomas, particularly with respect to alterations in the VHL-HIF signaling pathway and in the MET signaling cascade.
In the field of imaging, new techniques are being developed that enable earlier and more precise diagnosis. Functional imaging techniques such as dynamic contrast-enhanced MRI or PET-CT with tumor-specific tracers can provide additional information about tumor biology and metabolism. The application of artificial intelligence to the analysis of radiological images promises improved detection and characterization of kidney lesions.
In the field of minimally invasive surgery, advanced laparoscopic and robot-assisted techniques for nephrectomy and partial nephrectomy are being further developed. These procedures aim to reduce surgical trauma, faster recovery times, and improved cosmetic results while maintaining oncological principles.
Immunotherapy represents one of the most promising areas of research. Clinical trials with checkpoint inhibitors such as anti-PD-1/PD-L1 antibodies in dogs with various types of tumors, including renal carcinomas, show encouraging results. New approaches such as CAR-T cell therapies or tumor-specific vaccines are in preclinical development phases and could expand the therapeutic arsenal in the future.
In the field of targeted therapies, new generations of tyrosine kinase inhibitors with improved specificity and reduced toxicity are being developed. The combination of different targeted agents or their integration into multimodal therapy concepts is also being investigated. Biomarker-guided therapy decisions based on the molecular characterization of individual tumors could pave the way for personalized oncology in veterinary medicine.
Last but not least, the exploration of the tumor microenvironment is gaining in importance. The interactions between tumor cells, immune cells, and stromal components significantly influence tumor growth, metastasis, and therapy response. A better understanding of these complex interactions could open up new therapeutic strategies that target not primarily the tumor cells, but their environment.
These diverse research approaches fuel the hope for improved diagnostic and therapeutic options for dogs with renal adenocarcinoma in the future. The close collaboration between basic researchers, clinical veterinary oncologists, and human physicians will be crucial to drive innovation and ultimately improve the prognosis of affected patients.
Frequently asked questions (FAQs)
1. What is Renal Adenocarcinoma in Dogs?
A renal adenocarcinoma is a malignant tumor that originates from the epithelial cells of the kidney tissue. It can grow locally invasively and spread to other organs. According to Withrow & MacEwen’s Small Animal Clinical Oncology (6th edition), kidney tumors are among the rarer cancers in dogs, but require early diagnosis.
2. What Symptoms may Indicate Kidney Cancer in Dogs?
Initially, non-specific signs such as decreased appetite, weight loss, and increased thirst often occur. Later, bloody urine (hematuria), fatigue, flank pain, or a palpable tumor in the abdomen may be added. petsvetcheck.de strongly recommends a veterinary examination for these symptoms.
3. How is a Kidney Tumor Diagnosed?
- Blood and urine tests: Checking kidney function and tumor markers.
- Imaging: Ultrasound, X-ray, CT, or MRI for precise localization of the tumor and exclusion of metastases.
- Tissue sample (biopsy): Histopathological examination to confirm the diagnosis.
Standard works such as the BSAVA Manual of Canine and Feline Oncology describe fine needle aspiration as a helpful method if the location allows it.
4. What Treatment Options are Available?
- Surgical removal (nephrectomy): First choice if only one kidney is affected.
- Chemotherapy: for advanced cases or high risk of metastasis.
- Immunotherapy and targeted therapies: Are being increasingly researched.
According to Veterinary Ophthalmology (Gelatt et al.), an interdisciplinary approach is worthwhile if a tumor has already spread to other organ systems.
5. Is Surgery Always Possible?
If the tumor is limited to one kidney and the other kidney is healthy, complete removal is often feasible and offers a chance of cure or long-term control. In the case of bilateral changes or already far advanced metastases, surgery may be limited or only palliative.
6. What is the Prognosis?
The prognosis depends heavily on the tumor stage. If the adenocarcinoma is detected early and can be completely removed, the dog has a good chance of several tumor-free years. In metastasized tumors, the prognosis worsens significantly. Withrow & MacEwen’s Small Animal Clinical Oncology describes a median survival of 6 to 16 months, depending on the metastasis.
7. Can Kidney Tumors Spread to other Organs?
Yes, renal adenocarcinomas often spread to the lungs, liver, and local lymph nodes. Therefore, regular check-ups (e.g., chest X-rays, ultrasound) after surgery are essential to detect metastases early.
8. Are Certain Dog Breeds more Frequently Affected?
There is no clearly proven breed preference, but some studies (e.g., in larger breeds such as German Shepherd or Golden Retriever) discuss a possible accumulation. This may be due to genetic factors or a higher probability of examinations in certain breeds.
9. What Follow-Up Measures are Important?
- Regular check-ups: Blood pressure measurement, blood and urine tests, imaging procedures.
- Adapted diet: Special kidney diets relieve the remaining kidney.
- Observation of the general condition: Seek veterinary help early if there are any changes.
On petsvetcheck.de practical advice is given on how to handle dogs after surgery, e.g. calming down, wound care and monitoring the amount of water they drink.
10. What Role Does Nutrition Play in Dogs with Kidney Cancer?
A balanced, kidney-supporting diet can positively influence the organ function of the healthy (or remaining) kidney. Proteins should be provided in an appropriate amount, while excess minerals (especially phosphorus) are reduced. According to Slatter’s Textbook of Small Animal Surgery, an individually adapted diet can improve the quality of life and slow down the progression of kidney disease.