Repeated ultrasound tests could be used to identify an isolated gastric duplication cyst before surgery.

A toddler girl was diagnosed with intra-abdominal simple cyst in the splenic flexure at the gestational period. Due to a severe fever that persisted for 6 days, she was admitted to the emergency room. The diagnosis of intraperitoneal cyst infection was made after contrast-enhanced CT revealed an enlarged cyst and a heterogeneous contrast effect on the cyst wall. A double-wall sign was observed on the cyst wall during continuous ultrasound follow-up, which led to the preoperative diagnosis of the cyst as a duplication cyst. The double-wall sign and cyst peristalsis were identified via successive ultrasound examinations to support the cyst diagnosis. Identifying a duplication cyst based solely on symptoms alone is difficult because the condition may present in different ways.