Mucor pyelonephritis. Report of a case diagnosed by urine cytology, with diagnostic considerations in the workup of funguria.

BACKGROUND Isolated renal mucormycosis is an uncommon kidney infection affecting patients with underlying systemic diseases and intravenous (IV) drug abuse. We report a unique case in the cytologic literature in which urine cytology provided insight into the diagnosis, renal mucormycosis. CASE The patient, a diabetic and IV drug abuser, presented with complaints of left flank pain, fever and dysuria. All urine cultures were negative. A computed tomography (CT) scan showed changes consistent with left acute pyelonephritis, and the patient was treated for a presumed diagnosis of bacterial pyelonephritis. Late in the hospital stay, the cytology laboratory diagnosed Mucor in a single urine specimen, but the patient had already been discharged. The patient was never treated for funguria, only to present again with left flank pain 13 months later. An abdominopelvic CT scan showed progression to left chronic pyelonephritis. The patient, however, left the hospital against medical advice before any further workup could be completed. CONCLUSION Renal mucormycosis should be considered part of the differential diagnosis in patients with underlying diseases or IV drug abuse who present with symptoms of acute pyelonephritis. The differential diagnosis of Mucor funguria should also include fungal ball in the renal pelvis or urinary bladder and fungal cystitis.