GENERAL CONSIDERATIONS

General Considerations

•renal cystadenocarcinoma is an autosomal dominant condition in GSD with a genetic linkage to chromosome 5

•renal cystadenocarcinoma represent 6% of all renal tumors in GSD

•renal cystadenocarcinoma has also been described in a GSD-cross dog and Golden Retriever

•renal cystadenocarcinoma is a bilateral disease with slowly progressive deterioration of renal function

•renal cystadenocarcinoma is associated with nodular dermatofibrosis and uterine leiomyoma

•nodular dermatofibrosis is present in all cases and appear as small, firm, and mobile subcutaneous masses

Biologic Behaviour

•clinical signs are worse with bilateral disease and the size of skin and uterine tumors increase with advancing age

•metastasis reported in up to 47% of cases:

•metastatic sites including sternal and abdominal lymph nodes, liver, lungs, pleura, and peritoneum

•metastasis is more common with large, solid, and poorly differentiated tumors

•main causes of death are renal failure, metastatic disease and secondary skin infections

DIAGNOSIS

Clinical Signs

•clinical signs are non-specific such as abdominal enlargement and abdominal pain

•urinary signs are uncommon

•skin lesions (i.e., dermatofibrosis) are associated with renal cystadenocarcinomas in GSD

•lameness caused by either skeletal metastases or hypertrophic osteopathy

Urinalysis and Urine Sediment Cytology

•proteinuria is a common finding with renal tumors

•hematuria is uncommon

•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

Imaging

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

Clinical Staging

TREATMENT

Surgery

•surgical management depends on behaviour of the tumor, presence of metastases and bilateral renal involvement, and invasion of the caudal vena cava and adjacent structures

•nephroureterectomy is recommended for:

•malignant renal and ureteral tumors except LSA

•grading and staging of nephroblastoma

•nephron sparing techniques should be used for benign tumors and bilateral disease to reduce the risk of renal failure