Sonographic Findings of a Right Kidney Mass: A Case of the Month September 2022

Patient Information:

Age: 14 years
Gender: Neutered Male
Species: Canine
Breed: Beagle

History:

An abdominal ultrasound was recommended after a tense abdomen was noted on routine physical examination with a soft tissue mass seen on abdominal radiographs.

Image Interpretation:

Abdominal sonographic findings:

The right kidney is mass-like and severely increased in size (~ 7.3 x 10.2cm). Majority of the kidney is amorphous, having near-complete loss of normal corticomedullary junction distinction. A large anechoic cavitation (~ 4.6 x 5.9cm) is seen having a severely thin wall (Wall thickness: 1.7 mm) at the caudal pole. The cranial pole exhibits a discernible renal cortex with dilation of the diverticuli. The right kidney mass is moderately vascular on color doppler
The left kidney maintained normal sonographic appearance.
A homogenous and mildly hypoechoic liver nodule was also seen in the left liver, measuring ~ 2.0cm.

Sonographic appearance of the right kidney mass. Notice the large, thin-walled anechoic cavitation seen along the caudal pole.

Diagnosis and Sonographic Analysis:

The owner elected to have a nephrectomy performed. A 3 hour surgery was successfully completed by Dr. Neuman, and patient was reportedly BAR and eating shortly after being discharged from the hospital.

Due to the size of the right kidney, a cross section (~ 5.0 x 50 cm) of the kidney was sent to Antech for histopathology.

Images from surgery:

Right Kidney Mass

The large fluid-filled cavitation in the caudal pole can be seen during post-operative dissection.

Histopathology Results:

Received: 5.0 cm x 50 cm tissue.

Description:
The multiple sections of ovary examined had a multinodular malignant neoplastic process consistent with renal tubulopapillary cystadenocarcinoma. It was characterized by neoplastic proliferation of epithelial cells which formed irregular acinar and ductular structures or tubulopapillary pattern surrounding large areas of cystic cavitation which contained abundant pale eosinophilic to amphophilic secretion effacing normal architecture. The cells had round ovoid hyperchromatic nuclei with finely stippled chromatin and occasional centrally located nucleoli. The cytoplasm is scant to moderate eosinophilic with indistinct cell borders. Many acini contained pale eosinophilic homogeneous secretion. There was marked hydronephrosis with compression atrophy of the medulla.

Microscopic Findings: Renal Papillary Tubular Cystadenocarcinoma with Hydronephrosis

Comments:
Renal adenocarcinomas are rapid growing tumors and more prone to metastasis. Metastasis usually has occurred by the time the tumor is diagnosed. In dogs, 50-70% of renal cell carcinomas metastasize. The most likely sites are lung, liver and regional lymph node. The survival ranges for carcinomas was 0-59 months (median 16 months). Renal adenocarcinomas have propensity for invasion of the renal vein and may ascend up the posterior vena cava with early and frequent formation of pulmonary metastasis. Metastasis may also be seen in the liver, adrenals, and vertebrae. Widespead metastasis is common.

Special Thanks to St. Charles Animal Hospital and Antech for the interesting case and follow-up.