A retroperitoneal gastric duplication cyst mimicking a simple exophytic renal cyst in an adolescent.

Gastric duplications are rare anomalies and usually occur along the greater curvature of the stomach. The authors herein describe an uncommon case of a retroperitoneal gastric duplication, which was not found during previous emergency laparotomy for suspected peritonitis at another institution. On subsequent computed tomography scan, the lesion was misinterpreted as a simple exophytic renal cyst. Laparoscopy was undertaken because of unresolved symptoms, and a retroperitoneal duplication cyst was successfully excised. It was lined with gastric mucosa and islands of pancreatic tissue on pathologic examination.