| Summary points: | A 15-month-old Caucasian boy presents with a 6-week history of progressive abdominal distension. Physical examination, laboratory data, abdominal ultrasound, computed tomography (chest, abdomen, and pelvis), and exploratory laparotomy are described. The authors discuss the diagnostic dilemma of a multiocular renal cyst in which radiological imaging appears to be unreliable in differentiating benign cysts from malignant renal tumours. |