Fistulized renal cyst in the stomach: A diagnostic and therapeutic challenge.

Renal cysts are usually asymptomatic, and superinfection is rare. We report the case of a 90-year-old woman presenting with fever, flank pain, and vomiting. Laboratory tests showed leukocytosis and elevated C-reactive protein. CT imaging revealed an infected upper-pole renal cyst with inflammatory changes, without obstruction. Intravenous antibiotics (third-generation cephalosporin plus aminoglycoside) led to rapid improvement. Follow-up imaging demonstrated partial cyst regression and a small renogastric fistula, which closed spontaneously after one month of continued medical therapy. This case highlights an exceptionally rare complication of an infected renal cyst successfully managed without intervention.