Perirenal Pseudocysts in a Cat

Patient Information:

Age: 14 year-old
Gender: Neutered male
Species: Feline
Breed: Domestic short hair

History:

Pet was presented for an annual exam when a possible mass was felt on abdominal palpation. A grade 3/6 systolic murmur was also detected on cardiac auscultation.

Ultrasound Evaluation:

Kidneys: normal size (LT/RT: 4.0/3.9cm) and shape. Both kidneys had coarse moderately hyperechoic renal cortices which were disproportionately large. There was moderate to severe loss of the corticomedullary junction distinction as well as lobar scalloping. The right kidney contained one thin-walled anechoic fluid-filled structure consistent with cystic lesion measuring 0.8x0.9cm in diameter. A mild to moderate (left) to large (right) amount of anechoic fluid was seen surrounding the kidneys in the subcapsular space (see images). No pyelectasia was visualized.

Image #1. Longitudinal view of the left kidney using a high frequency linear probe.

Image #2. Longitudinal view of the right kidney using a high frequency linear probe.

Ultrasound-guided drainage:

Approximately 340mls of clear colorless fluid was removed from the right and 20mls from the left subcapsular spaces. Fluid sample was submitted for cytology and fluid analysis which revealed findings consistent with low cellularity cystic fluid.

Follow up and outcome:

Bloodwork revealed a creatine level of 2.4mg/dl (normal: 0.6-2.4mg/dl) and a BUN of 42mg/dl (normal: 14-36mg/dl) and renal diet was prescribed. A month later, the patient presented for partial anorexia and recurrence of the perirenal effusion was felt palpation. At that point, the owner opted for surgical referral for bilateral laparoscopic capsulectomy. The patient recovered well from surgery besides a slow worsening of the azotemia. But unfortunately, the cat had to be euthanized two months later due to the development of congestive heart failure as a complication of hypertrophic cardiomyopathy and severe left atrial enlargement.

Comments:

Subcapsular perirenal pseudocyst formation can occur at variable stages of renal dysfunction and develop secondary to progressive renal parenchyma contraction which impairs venous or lymphatic drainage resulting in transudation. Resection of the pseudocyst wall is usually effective in eliminating signs but does not stop the progression of the renal disease. The prognosis for cats with pseudocyst formation is related to the degree of renal dysfunction at time of diagnosis.

A retrospective study of 26 affected cats showed that nineteen (73%) affected cats were male. The median age was 11 years. Most presented for abdominal enlargement and had varying degrees of renal dysfunction. Thirteen cats (50%) had bilateral pseudocysts. Eight cats were treated surgically. Cats survived a median of 9 months after surgery and survival was correlated statistically to degree of azotemia at presentation. Percutaneous drainage of pseudocysts was ineffective in controlling long-term fluid accumulation.

Ochoa V et al. Perinephric Pseudocys in the Cat: A Retrospective Study and Review of the Literature. J Vet Intern Med 1999;13:47–55.

Beck JA et al. Perirenal Pseudocysts in 26 Cats. Aust Vet J 200 Mar; 78(3(: 166-71.

Special thanks to the staff at Adam’s Mill Veterinary Hospital for their help with this case.