Case Study

Left perirenal cyst in a 15 year old FS DMH cat

A 15 year old spayed female DMH cat was presented for progressive disease over a 6-8 month period, characterized by poor coat quality, decreased mobility, reduced activity, and pruritic skin lesions that have not responded to antibiotics and use of an E-collar. Abnormalities on physical examination were alopecia, hyperpigmentation, and thinning of the skin of the ventrum, and a non-healing, plaque-like, superficial skin lesion on the cranial aspect of the left stifle and accessory pad of the left carpus. Skin biopsies were scheduled. On urinalysis an inappropriate SG and proteinuria was present with a urine protein: creatinine ratio of 0.3. Abnormalities on serum biochemistry included hypercalcemia and hyperproteinemia. Radiographs showed arthritis of elbow, LS junction, and hips, as well as a mass in the region of the left kidney.

DX

Simple left perirenal cyst

Sonographic Differential Diagnosis

Left perirenal cyst with decreased normal renal parenchyma, consistent with chronic interstitial nephrosis. Compensatory right kidney hypertrophy with slight pyelectasia.

Image Interpretation

The left kidney in this patient revealed a perirenal cyst; normal renal parenchyma was significantly decreased. This kidney measured 2.0 cm with decreased power Doppler signal. The perirenal cyst itself measures approximately 5.6×7.0 cm. The right kidney appeared largely normal with slight pyelectasia and mild enlargement (5.96 cm). This is likely due to compensatory hypertrophy. Pyelectasia measured 0.23 cm, which is within physiologic range.

Clinical Differential Diagnosis

Mass in area of right kidney – neoplasia, cyst, pyelonephritis, abscess, hydronephrosis. Pancreatic neoplasia.

Sampling

Urine culture and sensitivity would be warranted. Drainage procedure was performed on the perirenal cyst, which reduced cystic volume by approximately half. No evidence of complications were noted after aspiration. Cystic fluid analysis revealed a pure transudate and was negative for evidence of neoplasia.