Infected Solitary Renal Cyst in an Elderly Woman With Chronic Urinary Retention

Solitary renal cysts are common in elderly individuals and are usually asymptomatic. Cyst infection is rare but should be recognized as a potential complication. We report an 89-year-old woman with an infected solitary renal cyst who presented with atypical symptoms, including only dizziness, anorexia, and malaise, without localizing signs. Laboratory tests showed elevated inflammatory markers and pyuria, and <i>Escherichia coli</i> was isolated from urine. Imaging revealed enlargement and wall thickening of a Bosniak category II right renal cyst with debris-like echoes. She improved with antibiotics alone. Chronic urinary retention due to neurogenic bladder was considered a possible contributing factor to the cyst infection.