+ General Considerations

  • Renal carcinoma is predominantly seen in older, male, medium-to-large breed dogs
  • Renal carcinoma is usually unilateral and large with left and right kidneys are equally affected
  • Renal carcinomas are classified as solid, tubular, and papillary on the basis of histologic patterns, however, most exhibit a mixed pattern

+ Biologic Behaviour

  • Invasion of caudal vena cava and tributary veins with the development of a tumor thrombus has been reported and can complicate surgical treatment
  • Paraneoplastic syndromes: polycythemia and neutrophilic leukocytosis
  • Metastatic disease is common:
  • 60% metastatic rate in cats
  • 54% metastatic rate to the lungs in dogs, 54% to abdominal organs, and 27% to the regional lymph nodes
  • Metastatic sites include the lungs, liver, ipsilateral adrenal gland, regional lymph node, contralateral kidney, omentum, peritoneum, diaphragm, skin, heart, brain, and appendicular and axial skeleton



  • Clinical signs are non-specific such as abdominal enlargement and abdominal pain
  • Urinary signs are uncommon
  • Lameness caused by either skeletal metastases or hypertrophic osteopathy
  • Paraneoplastic polycythemia may be more common with renal tumors as majority of renal carcinomas involve the proximal convoluted tubule which is the main site of erythropoietin production

+ Urinalysis and Urine Sediment Cytology

  • Proteinuria is a common finding with renal tumors
  • Hematuria is uncommon with renal carcinoma, but can be seen with HSA, hemangioma, and renal pelvis TCC
  • Urine sediment cytology is rarely diagnostic for renal tumors

+ Blood Tests

  • Hematology and serum biochemistry findings are usually normal or non-specific
  • Mild-to-moderate normochromic, normocytic anemia can be caused by either hematuria or bone marrow suppression secondary to chronic disease
  • Polycythemia is a reported paraneoplastic syndrome with renal tumors
  • Uremia may result from obstruction of urinary outflow, bilateral renal tumors, or age-related renal failure


+ General Considerations

  • Survey abdominal and thoracic radiographs, contrast radiography, ultrasonography, CT, and MRI are imaging modalities used to identify the presence and extent of renal tumors

+ Survey Abdominal Radiography

  • Survey abdominal radiographic findings: sublumbar lymph node enlargement, renomegaly, and skeletal metastases, especially lumbar vertebrae and pelvis
  • Abdominal mass is identified in 81% and localized to the kidney in 54% of dogs with primary renal tumors
  • Focal mineralization can be observed but difficult to differentiate tumor from renal calculi and GI opacities

+ Excretory Urography

  • Excretory urographic findings: space occupying renal mass, variable opacification of the renal parenchyma, and distortion of the renal pelvis
  • Excretory urography successfully identifies a renal mass in 96% dogs with primary renal tumors

+ Ultrasonography

  • Ultrasonography results in earlier diagnosis and more successful treatment of renal neoplasia in humans
  • Renal tumors, except for LSA, produce a mixed echogenicity with disruption of the normal renal architecture
  • Renal LSA is usually hypoechoic
  • Ultrasonography is also useful in detecting neoplastic involvement of regional lymph nodes and adjacent structures such as the adrenal glands ± caudal vena cava

+ Advanced Imaging

  • CT scans are used for the diagnosis and local staging of renal neoplasia with a high correlation between CT findings and gross pathology
  • MRI is preferred for identifying adjacent vascular and visceral invasion, especially if renal-sparing surgery is planned
  • Other imaging techniques include caval venography and nuclear scintigraphy

+ Biopsy

  • Biopsy is required for definitive diagnosis of renal tumors
  • Biopsy techniques: FNA, needle biopsy, and wedge biopsy
  • FNA and needle-core biopsy can be performed using a blind, ultrasound-guided, laparoscopic, or open technique
  • Ultrasound-guided biopsy is a rapid, safe, and accurate technique for diagnosing focal and diffuse renal disease
  • Blind percutaneous needle biopsy can be performed in cats where the kidney can be immobilized by palpation
  • Percutaneous biopsy should be performed with bilateral renal lesions or suspected renal LSA
  • Single procedure surgical biopsy, staging, and definitive treatment preferred for unilateral lesions
  • Complications of needle biopsy: minor localized hemorrhage, microscopic hematuria, and tumor seeding

+ Prognosis

  • MST 8-16 months for dogs with renal carcinoma
  • However, surgical resection has resulted in prolonged survival times of up to 4 years
  • Paraneoplastic polycythemia is a poor prognostic sign in humans, but not animals
  • Poor survival time in animals reflects the advanced stage of disease at diagnosis, difficulty in completely excising the tumor, and high metastatic rate



T0 No evidence of neoplasia
T1 Small tumor without deformation of the kidney - Primary Tumor
T2 Single tumor with deformation ± enlargement of the kidney
T3 Tumor invading perinephric structures ± pelvis or ureter ± renal blood vessels
T4 Tumor invading adjacent organs
M0 No evidence of metastasis
M1 Evidence of distant metastasis with site specified with (a) single metastasis, (b) multiple metastasis in 1 organ, and (c) multiple metastasis in ≥ 2 organs - Metastasis
N0 No evidence of regional lymph node involvement
N1 Ipsilateral regional lymph node involvement - Node
N2 Bilateral regional lymph node involvement
N3 Distant lymph node involvement