A 57-year-old male patient presented with fever, general malaise, weight loss, and chronic right flank pain. He first noticed a cutaneous discharge at the right lower quadrant 3 weeks ago. His medical history included extracorporeal shock wave lithotripsy of the right kidney years ago and recurrent urinary tract infection. Laboratory studies revealed leukocytosis (14.26/mL, range 4-10/mL) and elevated C-reactive protein level (43.02 mg/L, range 0-5 mg/L). Serum creatinine level was within a normal range (95 micromol/L, range 62-106 micromol/L). Urinalysis was normal and urine culture was negative. A 1 cm cutaneous opening with yellowish discharge was seen at the right lower quadrant. Real-time polymerase chain reaction (PCR) of the urine and pus were negative for Mycobacterium tuberculosis. A chest X ray appeared normal.
Plain abdominal radiography demonstrated a small right kidney shadow with compacted stones (Figure 1). A 4-phase low-dose computed tomographic (CT) urography was indicated. Pre-contrast images revealed an atrophic and deformed right kidney with multiple nephrolithiasis, parenchymal calcification, multifocal fat deposits throughout the renal parenchyma, and perirenal fat stranding (Figure 2). Gas was not evident. On serial contrast images, the renal parenchyma was completely destroyed and the pyelocalyceal system was unrecognizable. A loss of differentiation between the anterior renal parenchyma and second portion of the duodenum was also appreciated, suggesting an adhesion. Renal function was not seen in the delayed excretory phases, implying a severely impaired kidney function. The right ureter was dilated (# 10 mm) with wall thickening and intraluminal hyper-attenuation compared to the contralateral normal counterpart (Figure 3). Hydronephrosis and perirenal abscess were not observed in all phases.
A 7.5 cm x 6 cm x 3.5 cm fluid collection was found at the right lower quadrant, confined within the right iliac muscle. The collection had a thick enhanced wall and a 1 cm cutaneous opening. The right ureter was found to empty at the medial margin of the collection, indicating a chronic ureteral iliac muscle fistula. The "run-off" ureter was not seen on any delayed phases even with the patient was on prone position. The adjacent bony and vascular structures appeared normal. Other abnormality was a left kidney stone.
A CT fistulography was consequently performed which demonstrated a complex fistula from the intramuscular collection, connecting with the distal ureter upward to the right pyelocalyceal system and communicating with the adjacent duodenum (Figure 4), corresponding to stage III according to Malek and Elder   classification. There was no evidence of nephrobronchial fistula. XGP was highly suspected. Surgical exploration through a midline incision confirmed the presence of a pyeloduodenal and a ureteromuscular fistula. Right total nephrectomy, abscess evacuation, and fistula closure were performed. Escherichia coli and Streptococcus viridans were isolated on pus culture.
Pathological examination of the resected kidney confirmed diffuse XGP. Microscopically, the lesion had three distinct zones centered by a calyx. The inner zone consisted of leukocytes, lymphocytes, plasma cells, histiocytes or macrophages, and necrosis. The middle zone consisted of granulation tissues surrounded by hemorrhage. The classic feature was the presence of lipid-laden foamy macrophages (xanthoma cells) that gave a yellow color to the tissue. The outer zone consisted of giant cells, cholesterol clefts, and fibrous tissues. In addition, various degrees of renal tubular atrophy and tubular dilatation were also observed (Figure 5). At immunohistochemistry, the lesion was positive for CD68 and vimentin, and negative for smooth muscle actin (SMA), desmin, and epithelial markers (Figure 6). Michaelis-Gutmann bodies were not evident; therefore, malakoplakia was excluded.
The patient was discharged uneventfully after 10 days and was sent home on oral antibiotics. He has been doing well without recurrent fistula or abscess during 15-month follow-up.