Case Study

Pyelonephritis in a 5 year old FS DLH cat

A 5-year-old FS DLH cat was presented for hiding at home and anorexia. Abnormalities on physical examination included a large urinary bladder and mild dehydration. Leukocytosis was present on CBC; blood chemistry was within normal limits. Survey abdominal radiographs showed left-sided renomegaly and a small right kidney.

Sonographic Differential Diagnosis

The appearance of the hydronephrotic left kidney is either due to a ureteral obstructive process or to severe pyelonephritis. Given the echogenic fluid in the center of the left kidney, pyelonephritis is certainly suspected. The cystic fluid surrounding the left kidney is either due to subcapsular or perirenal fluid accumulation secondary to pyelonephritis or could be an initial perinephric pseudo-cyst. It is hard to differentiate which process came first at this point in time.

Image Interpretation

The right kidney measured 4.42cm and was normal in size with normal cortical echogenicity and corticomedullary distinction. The left kidney was very abnormal with a large perirenal cyst measuring 5.27cm. Within the fluid filled structure, the left kidney was visualized. The kidney had only a thin cortical layer present with complete severe hydronephrosis and destruction of the internal architecture. The fluid within the cyst and within the left renal pelvis was echogenic with wispy fibrin strands. The left ureter could be followed for a short while but no obvious obstructive lesions noted. The urinary bladder was normal in appearance, and there was no evidence of any masses, stones, sediment within the bladder.

DX

Severe pyelonephritis.

Outcome

Abdominal radiographs revealed a large left kidney with no evidence of any nephroliths or ureteroliths. An IVP was performed after the ultrasound exam which showed an extended emptying time into the bladder (>45 minutes). The patient was treated with long-term antibiotic therapy, and at the last communication, the owner reported that patient was doing well on current therapy.

Comments

Given that the right kidney is completely normal and the left kidney is completely full of purulent material, a unilateral nephrectomy is strongly advised.

Clinical Differential Diagnosis

Hydronephrosis, pyelonephritis, renal neoplasia

Sampling

A fine needle aspirate of the left renal pelvis revealed a large amount of pus/white opaque mucoid fluid. This is consistent with severe pyelonephritis. Bacterial culture yielded no growth.