Malignant paraganglioma in a cougar (Puma concolor)

Imaging features of retroperitoneal extra-adrenal paragangliomas in 10 dogs

Retroperitoneal paragangliomas are rare tumors of the neuroendocrine system. Only a few canine case reports are available with rare descriptions of their imaging features. The objectives of this multi‐center, retrospective case series study were to describe the diagnostic imaging features of confirmed retroperitoneal paragangliomas and specify their location. Medical records and imaging studies of 10 affected dogs with cytological or histopathologic results concordant with retroperitoneal paragangliomas were evaluated. Dogs had a median age of 9 years. Four of them had clinical signs and laboratory reports compatible with excessive production of catecholamines. Six ultrasound, four CT, four radiographic, and one MRI studies were included. The paragangliomas did not have a specific location along the aorta. They were of various sizes (median 33 mm, range: 9–85 mm of length). Masses had heterogeneous parenchyma in six of 10 dogs, regardless of the imaging modality. Strong contrast enhancement was found in all CT studies. Encircling of at least one vessel was detected in six of 10 masses, clear invasion of a vessel was identified in one of 10 masses. In five of 10 cases, the masses were initially misconstrued as lymph nodes by the on‐site radiologist. Retroperitoneal paragangliomas appear along the abdominal aorta, often presenting heterogeneous parenchyma, possibly affecting the local vasculature, and displaying strong contrast enhancement on CT. Clinical signs can be secondary to mass effects or excessive catecholamine production. Underdiagnosis and misdiagnosis of this tumor are suspected as they can be silent, of small size, or confused with other structures.

Subcutaneous ureteral bypass for treatment of bilateral ureteral obstruction in a cat with retroperitoneal paraganglioma

CASE DESCRIPTION A 7-year-old female domestic shorthair cat was referred for evaluation of azotemia and unilateral hydronephrosis. CLINICAL FINDINGS Abdominal ultrasonography revealed right-sided hydronephrosis and dilation of the proximal aspect of the ureter; the left kidney was small with irregular margins. A highly vascular, irregular retroperitoneal mass, not clearly associated with the ureteral obstruction, was also visualized. Surgical exploration confirmed a retroperitoneal mass involving the caudal mesenteric artery and both ureters, with hydroureter on the right side. TREATMENT AND OUTCOME A subcutaneous ureteral bypass (SUB) device was surgically implanted to treat right ureteral obstruction, and the mass was biopsied. Shortly after surgery, progressive azotemia and hyperkalemia were detected; ultrasonographic examination revealed left-sided hydronephrosis and hydroureter, which was suspected secondary to inflammation of the mass causing a left-sided ureteral obstruction. A second surgery was performed to place an SUB device for the left kidney and remove the retroperitoneal mass; both ureters were ligated at the mid- and distal aspects and then transected and removed with the mass. A neuroendocrine paraganglioma was identified by histopathologic evaluation of the mass. Hydronephrosis improved (right kidney) or resolved (left kidney) after surgery, and azotemia improved. Chemotherapeutic intervention was declined. Markers of renal function were static during the 14-month follow-up period. At the last follow-up evaluation, the patient was reportedly doing well, and both SUB devices were patent. CLINICAL RELEVANCE This was the first report of retroperitoneal paraganglioma in a domestic cat causing bilateral ureteral obstruction. Bilateral SUB device placement enabled en bloc mass resection and provided long-term relief of ureteral obstruction.