+ 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

• 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