SURGICAL MANAGEMENT OF A PARARENAL PSEUDOCYST IN A FERRET (MUSTELA PUTORIUS FURO)

Development of renal adenocarcinoma in a ferret with renal cortical cysts (Mustela putorius furo)

CASE DESCRIPTION

A 5.5-year-old 0.929-kg spayed female domestic ferret (Mustela putorius furo) underwent serial abdominal ultrasonographic and clinicopathologic examinations after multiple renal cysts were detected bilaterally during a routine examination.

CLINICAL FINDINGS

The ferret was apparently healthy at the start of the monitoring period and had no clinical signs for > 20 months. Four months after the initial examination, the largest cyst became increasingly mineralized; 17 months after detection, it had increased in size and become amorphous, and the ferret's plasma BUN concentration was mildly high. Within 21 months after the first visit, a nodule was detectable, and hydronephrosis developed in the kidney with the largest cyst. Findings for fine-needle aspirates from the nodule were consistent with renal carcinoma.

TREATMENT AND OUTCOME

Contrast-enhanced CT revealed severe unilateral nephromegaly with no contrast uptake in the affected ureter. Following surgical removal of the affected kidney, histologic examination identified renal adenocarcinoma replacing the entire renal cortex and medulla. The ferret was euthanized postoperatively because of declining condition. On necropsy, metastasis to a mesenteric lymph node was identified; comorbidities included 2 other neoplasms and acute, severe injury of the contralateral kidney.

CLINICAL RELEVANCE

Neoplastic transformation of a renal cyst was suspected in the ferret of this report on the basis of observed ultrasonographic changes over time and extensive infiltration of the neoplasm throughout the affected kidney. Renal cysts are linked to renal neoplasia in other species, and the findings for this patient supported the need for periodic monitoring of renal cysts in ferrets.

Diagnostic Imaging of the Renal System in Exotic Companion Mammals

Radiographs can be used to easily visualize common types of urinary calculi in all parts of the urinary tract. Positive-contrast excretory urography and cystourethrography are sensitive to diseases within the ureters and urethra, most commonly obstruction. Ultrasound is widely available and noninvasive and can be used to evaluate renal architecture, ureteral dilation, urinary bladder wall disease, and urolithiasis. Computed tomography is increasing in availability and provides a large amount of cross-sectional information quickly and noninvasively. Multiple imaging modalities can be used to estimate or quantify glomerular filtration rate.