Infected Renal Cyst: Elusive Diagnosis and Percutaneous Management.

Background: Benign renal cysts are relatively common in older adults, usually found incidentally on CT. However, an infected renal cyst is a rare complication. While a course of antibiotic therapy is generally the first-line treatment, indications for definitive operative intervention include chronic pain, recurrent urinary tract infection, hematuria, abscess formation, and/or impaired renal function. Case Presentation: A 61-year-old male urologist with no significant medical history was hospitalized at an outside facility for fever, chills, and abdominal pain. Initial diagnosis was pyelonephritis in the setting of a recently passed stone, with absence of hydronephrosis and a large, simple right renal cyst, but he failed to improve with intravenous antibiotics and developed intractable hiccups. Serial CT scans demonstrated onset of mild upper pole hydronephrosis and no change in the benign-appearing simple cyst. Interventional radiology planned drainage of the upper pole calices with a diagnosis of infundibular stenosis, but upon insistence of a urology consultant who suspected occult infection of the cyst, drains were placed into the collecting system and the cyst, with the return of a jet of purulent fluid upon cyst puncture. Conclusion: The patient subsequently recovered and was discharged and seen at our facility where he was definitively treated with percutaneous endoscopic marsupialization of the cyst into the collecting system and fulguration of the infected cyst wall with complete resolution.