Gastric duplication cyst mimicking an adrenal-region cyst: a diagnostic challenge

Gastric duplication cysts (GDCs) are rare congenital malformations that may mimic adrenal or retroperitoneal cysts. Misdiagnosis can delay proper management. We report a unique case of a GDC that was misdiagnosed as a left adrenal cyst, with reversible hyperreninemia and indirect hyperbilirubinemia.

A 28-year-old asymptomatic man was incidentally found to have a left adrenal cyst on ultrasound. CT revealed a 4.1 × 5.5 cm non-enhancing unilocular cyst with preserved adrenal structure. Laboratory tests showed elevated upright plasma renin concentration (63.3 pg/mL) and indirect bilirubin (57.6 μmol/L). During laparoscopic excision, a cyst arising from the gastric fundus was identified. Pathology confirmed a non-communicating GDC lined by gastric mucosa and smooth muscle. Three months postoperatively, renin and bilirubin levels normalized.

Ectopic GDCs in the adrenal region are extremely rare and often misinterpreted radiologically. The postoperative normalization of renin and bilirubin raises a possible association, but the mechanisms remain speculative, and causality cannot be established from this single case. Intraoperative cyst-fluid analysis and multidisciplinary evaluation assist in accurate diagnosis. Complete resection provided definitive diagnosis and a favorable short-term outcome in the present case; however, longer follow-up is required to assess recurrence and sustained biochemical remission.

GDC should be considered in adrenal-region cystic lesions with atypical features. Total excision provides both definitive diagnosis and a favorable short-term outcome, although longer surveillance is required.