We report a neonatal case of “intraluminal” pyloric duplication cyst, causing gastric obstruction after birth. Endoscopy revealed a submucosal cystic lesion approximately 15 mm in size arising from the anterior and inferior surfaces of the pylorus obliterating the pyloric canal. After laparotomy, intraoperative cholangiography was performed, which documented no communication between the cyst and the bilio-pancreatic duct. Gastrotomy was performed transversally over the antrum, and the cyst delivered through the incision. The cyst was incised, the upper part of the cyst wall removed, and a mucosectomy performed on the inner cyst wall of the lower part. The mucosa and muscle of the margin of the cyst were approximated. At follow up of 10 months, the patient is well without any sign of gastric obstruction.

Gastric duplication is a rare anomaly which account for only 3.8% of all gastrointestinal duplication. Gastric duplications are usually cysticlesion without communication with lumen. Most frequent presentation is an abdominal mass with vomiting, mainly diagnosed within the first year of life. Surgical removal is necessary in all cases, and optimal timing for surgery is the time that diagnosis is made. However, prenatally diagnosed gastric duplication is getting more common, and determining timing for surgery is not easy due to absent or minimal symptoms just after birth. We experienced prenatally diagnosed gastric duplication in a female newborn baby that gastric duplication was suggested in 24^th week of gestational age through prenatal ultrasonogram. Surgical removal was done at 3 months after birth, and showed good results. We think that natural history of gastric duplication and prevalent age of surgical disease which is similar to gastric duplication such infantile hypertrophic pyloric stenosis should be considered when timing of surgery on prenatally gastric duplication is decided.