Gastric bypass surgery is the most popular type of weight loss surgery in the United States, according to the Mayo Clinic. Gastric bypass surgery can be done through open surgery or laparoscopically. Gastric bypass is considered a major surgery that reduces the size of the stomach and re-routes the small intestine. It can have short-term and long-term complications that may require additional surgeries or changes in lifestyle.

Ulcers

Gastric bypass complications that occur four years post-op are considered long-term complications. According to the Mayo Clinic ulcers occur in 5 percent of people with gastric bypass surgery and are more common in people who take aspirin or nonsteroidal anti-inflammatory agents, or NSAIDS. Ulcers may be treated with medications but may also require avoidance of certain foods known to aggravate ulcers like spicy or acidic foods, citrus and alcohol.

Hernia

A hernia is a weakness in the incision site that may cause bulging of tissue and occurs in 15 percent of patients who have had open surgery but only 2 percent of patients who have had laparoscopic gastric bypass surgery, according to the Mayo Clinic. A hernia may require surgical repair depending on its severity. According to the University of Rochester Medical Center, or URMC, up to 20 percent of patients who have had a roux-en-Y gastric bypass, a type of gastric bypass surgery, require follow-up surgery to correct problems like hernias.

Nutrient Deficiencies

The Weight Control Information Network says gastric bypass patients may experience nutrient deficiencies due to malabsorption of essential vitamins and minerals. Nutrient deficiencies can lead to anemia, a blood disorder, neurological complications, permanent nerve damage and bone disorders like osteoporosis. As a result, patients who have undergone gastric bypass surgery are often required to take vitamin and mineral supplements.

Dumping Syndrome

Dumping syndrome occurs when food moves too quickly through the stomach and small intestine, according to Medline Plus. Dumping can cause nausea, vomiting, diarrhea, dizziness and sweating. Other long-term digestive problems that occur with gastric bypass surgery include heartburn and gastritis. Gastritis occurs when the stomach lining gets inflamed and can cause abdominal pain, indigestion, loss of appetite, nausea and vomiting.

Other Complications

Experts at the Mayo Clinic say the narrowing of the opening between the stomach and small intestine can result from gastric bypass surgery. Narrowing is considered a rare complication but may require surgical repair. Other long-term complications of gastric bypass surgery include kidney stones, gallstones and dehydration. Kidney stones occur due to a change in how the body absorbs minerals like calcium and oxalate and according to Medline Plus gallstones are associated with rapid weight loss. Dehydration can occur because patients are unable to drink enough fluid due to the small size of their stomach.