Gastric duplication malformation, also known as double stomach, is extremely rare clinically and accounts for approximately 9% of all GI malformations. The incidence of this disease has been reported in isolated cases and the incidence in the population is unknown. According to available data, the disease is more common in children and adolescents, with slightly more females than males. Most patients develop intermittent vomiting within the first 2 years of life, with vomitus consisting mostly of gastric contents and undigested food. In addition, there are symptoms such as poor appetite, epigastric discomfort, dull pain, anemia, weight loss and malnutrition. If the ducts of the ectopic pancreas are connected to both stomachs, the symptoms are recurrent pancreatitis. If ulcers occur in both stomachs, blood may enter the intestine through the ducts of the ectopic pancreas and symptoms of black stool or upper gastrointestinal bleeding may occur. The abdominal examination usually reveals a cystic mass in the upper abdomen, which is superficial and may move. Intermittent vomiting with predominantly undigested food in the stomach. Clinical manifestations include cystic masses in the upper abdomen, anemia, and malnutrition. Ancillary tests: barium gastric imaging may show a cut in the greater curvature of the stomach or a round mass protruding into the gastric lumen causing pyloric stenosis; endoscopic ultrasound shows a cyst attached to the outer layer of the stomach; gastroscopy may reveal a cystic mass protruding into the gastric sinus or pylorus. They should be differentiated from mesenteric cysts. Mesenteric cysts can be congenital developmental anomalies, such as intestinal-derived cysts, colonic mesenteric plasmacytoma, and dermatomal cysts. There are also parasitic cysts, traumatic (hemorrhagic cysts, inflammatory cysts), etc. Most of the tumors are substantial masses, which can be benign or malignant, and malignant tumors account for about 60% of the substantial masses. Plasmacytoid cysts are covered with mesothelial cells and usually occur in the mesentery of the transverse colon and sigmoid colon. The size of the cysts varies from several centimeters to 20 centimeters and are mostly solitary single-compartment cysts. Isolated cysts can be removed, and if the cyst is closely related to the intestinal canal or adheres to the mesenteric vessels, it can be removed together with part of the small intestine. Malignant tumors are often not in the early stage of the disease when they are diagnosed, and the radical resection rate is low, and their prognosis is very poor.