The side effects from stomach surgery include bleeding, heartburn, nausea, diarrhea and abdominal pain, says the American Cancer Society. The patient may need to take supplemental vitamins if parts of the stomach that produce vitamins are removed.
The patient's diet may also need to be changed, according to the American Cancer Society. He may need to eat small meals a few times a day instead of a large meal three times a day, for example. In rare cases, the connection between the stomach and the small intestine leaks, and nearby organs are damaged by the surgery.
People also have stomach surgery to help them to lose weight, according to MedicineNet. The stomach may be drastically reduced in volume or bypassed altogether. If the stomach's volume is reduced, the patient may suffer from vomiting if she does not chew her food thoroughly. Dumping syndrome is a risk for patients who have had bypass surgery. In this side effect, the food rushes through the small intestine. The patient suffers nausea, sweating, diarrhea, faintness and weakness that is very pronounced when she eats sweets.
Like patients who have had stomach surgery for cancer, patients of weight loss surgery may need supplementation to avoid anemia and osteoporosis, says MedicineNet. Other patients develop gallstones and hernias. The staples used to make the stomach smaller may become undone, and a woman must delay pregnancy until her weight stabilizes.