Diagram of the stomach, showing the different regions.

A gastrectomy is a partial or full surgical removal of the stomach. The first successful gastrectomy was performed by Theodor Billroth in 1881 for cancer of the stomach. Gastrectomies are performed to treat cancer, severe cases of peptic ulcer disease, and perforations of the stomach wall. This prodedure is becoming less common as peptic ulcers are now often treated with antibiotics for Helicobacter pylori or by endoscopy.

In severe duodenal ulcers it may be necessary to remove the lower portion of the stomach called the pylorus and the upper portion of the small intestine called the duodenum. If there is a sufficient portion of the upper duodenum remaining a Billroth I procedure is performed, where the remaining portion of the stomach is reattached to the duodenum before the bile duct and the duct of the pancreas. If the stomach cannot be reattached to the duodenum a Billroth II is performed, where the remaining portion of the duodenum is sealed off, a hole is cut into the next section of the small intestine called the jejunum and the stomach is reattached at this hole. As the pylorus is used to grind food and slowly release the food into the small intestine, removal of the pylorus can cause food to move into the small intestine faster than normal, leading to dumping syndrome.

In the past a gastrectomy for peptic ulcer disease was often accompanied by a vagotomy , where the vagus nerve is cut to reduce acid production in the stomach. Nowadays, this problem is managed with proton pump inhibitors.