Unusual case of urothelial carcinoma disguised as xanthogranulomatous pyelonephritis and causing reno-colic fistula: Case report and review of literature

Xanthogranulomatous pyelonephritis is a rare and aggressive form of chronic pyelonephritis, it can occur at all age groups but is more common in women than in men, supposedly relating to the increased incidence of urinary tract infections and chronic nephrolithiasis in woman. Computed tomography (CT) findings are very helpful in making the correct diagnosis, but the definitive diagnosis is still based on histology, as there are many differential diagnoses such as renal cell carcinoma and renal tuberculosis. The complications of this type of pyelonephritis are due to the involvement of adjacent organs. The most frequent ones are Psoas abscess, perinephric abscess, and sepsis. Nephrocutaneous and renocolic fistulas are less common. We report a case of a 61-year-old male, who presented to emergency for left-sided lumbar pain for whom radiological investigations confirmed a renocolic fistula complicating xanthogranulomatous pyelonephritis. The diagnosis of XGP was proven by histopathological examination of the nephrectomy specimen slides, but there was also association with an underlying malignant squamous differentiation consistent with urothelial carcinoma, which was not evident on CT. XGP is a rare variant of chronic pyelonephritis with known imaging features. The treatment of choice is nephrectomy and histopathological examination is required for final diagnosis, as there may be associated renal malignancy.