Signalment: 5 Year old Boer Wether

History:

• First seen 5 months prior for obstructive urolithiasis and concurrent pyelonephritis (E coli and Pseudomonas) which were corrected via tube cystotomy and treatment with antibiotics.
• Presented for evaluation of fever and lethargy.
• The dorsal aspect of the right flank was grossly distended compared to the left flank.

• Multicameral cystic mass originating along the lateral aspect of the right kidney.
• Medially displacing and effacing the lateral margin of the right kidney.
• No evidence of pyelectasia or nephrolithiasis.

• Lateral to the right kidney and extending caudally, there is a 24 cm x 14 cm x 15 cm cavitated mass with a thick, irregularly margined, contrast-enhanced rim. The mass contains a mixture of septated fat and non-contrast enhancing fluid. The contrast-enhancing rim of the mass partially surrounds the lateral aspect of the right kidney, medially displaces the right kidney and distorts its shape without evidence of invasion.
• The right ureter is medially displaced and indistinct from the mass in the in the mid lumbar region. Radiating from the mass are multiple contrast-enhancing streaks of soft tissue that efface with the lumbar vasculature and hypaxial musculature (aorta, caudal vena cava, quadratus lumborum and psoas muscles). Additional streaking soft tissue effaces the right dorsal body wall. There is no evidence of adjacent periosteal reaction of the ribs or vertebrae and no evidence of discospondylitis.
• Within the right renal cortex there are multiple linear to wedge shaped filling defects during the nephrogram phase. The right kidney is mildly enlarged as compared to the left although this is difficult to evaluate due to the distortion of the right kidney. There is no evidence of pyelectasia.
• Extending from the right ventral aspect of the urinary bladder is lobular heterogeneously contrast- enhancing soft tissue which effaces with the ventral abdominal wall and extends into the adjacent subcutaneous tissue. Within this material there are multiple discrete peripherally contrast-enhancing nodules with irregular margins, the largest measures 1 cm in diameter. (This region corresponds to the reported site of the prior cystostomy tube). There is a mild amount of peritoneal effusion.

1. Large cavitated, right perirenal mass. This finding is most consistent with a retroperitoneal abscess containing omental fat. Differential diagnoses include a walled off retroperitoneal infection possibly secondary to pyelonephritis vs. leakage of the cystotomy tube causing a peritoneal abscess.

2. Caudal abdominal abscessation, peritonitis and likely fibrosis secondary to infection of the removed cystotomy tube.

3. Right renal infarction and mild enlargement. Differential diagnoses include possible glomerulonephritis versus artifactual appearance of enlargement due to renal distortion from the mass.

Discussion and Further Plan:

It was suspected in this case that the cavitated mass originated from an ascending urinary infection and imaging features were consistent with abscessation.

Surgery was recommended and performed to remove the perirenal mass.

No reports in current literature discussing perirenal abscesses in goats.

Abscess formation in the goat is more commonly found associated with lymph nodes (caseous lymphadenitis) and CT findings have been described. Complications of tube cystotomy in goats have been reported.

Perirenal abscesses are more common in cattle. There are a few reports in dogs, cats, humans and a camel. These cases have concurrent pyelonephritis. Typical isolates in cattle are Corynebacterium with E. coli and Pseudomonas being less commonly reported.

• Braun, U., Hilbe, M., Nuss, K., Tschoner, T. Clinical, ultrasonographic and postmortem findings in a goat with abscessation of the mesenteric lymph nodes, Veterinary Record Case Reports 3:2015, e000174.
• Zatelli, A. and D’Ippolito, P. Bilateral perirenal abscesses in a domestic neutered shorthair cat JVIM 2004;18:902-903.
• Braun U, Nuss K, Wehbrink D, et al. Clinical and ultrasonographic findings, diagnosis and treatment of pyelonephritis in 17 cows. Vet J:2008; 175:240–248.
• Tharwat M, Sadan M, El-Shafaey ES, Saeed EH, Al-Hawas A. Bilateral renal abscessation and chronic active pyelonephritis in a male camel (Camelus dromedarius) caused by Escherichia coli. J Vet Med Sci. 2018;80(5):778–783. doi:10.1292/jvms.17-0484
• Rakestraw PC, Fubini SL, Gilbert RO, Ward JO. Tube cystostomy for treatment of obstructive urolithiasis in small ruminants. Vet Surg. 1995 Nov-Dec;24(6):498-505.