Gastric Bypass Risks and Complications


General vs. GBP-Specific

When you consider the risks of Gastric Bypass Surgery, they are divided into two groups: the risks of surgery in general and the risks specific to the Gastric Bypass.

The following surgical complications themselves can happen with any surgery. The risks of the complication occuring with the Gastric Bypass are outlined below.


The national mortality rate for gastric bypass surgery is 1 in 1000 patients, this is less than the mortality rate for having your gallbladder out. The death rate varies tremendously between surgeons and programs, so you must ask each surgeon this question directly. Know that “surgical mortality” is officially defined as any death, for any reason, within 30 days of an operation. Dr. Ellner's personal mortality rate is 0.

Wound Infection

Wound infections are less likely to occur with laparoscopic surgery than with the traditional open incision. However, patients with diabetes are at higher risk for developing wound infections after any type of surgery and obese patients require larger doses of antibiotics to prevent post-operative infection. Wound infections are treated with antibiotics and incision care.


Obese patients require more aggressive post-operative respiratory care to prevent fluid build-up in the lungs that can lead to pneumonia. Patients who undergo the laparoscopic technique (vs. the open incision) are much more comfortable after surgery, and are therefore more able to do the coughing and deep breathing that prevents pneumonia. Depending on the severity of the pneumonia, it may be treated on an outpatient basis with antibiotics or in the hospital with IV antibiotics and breathing treatments.

Deep Vein Thrombosis/Pulmonary Embolism

Because patients who undergo the laparoscopic technique (vs. the open incision) are much more comfortable after surgery, they are more able to walk and prevent the development of blood clots in the legs (deep vein thrombosis) that can lead to pulmonary embolism (clot breaking off and landing in the lung artery), and death. The treatment for DVT is blood thinners. The treatment for PE can require lysing (dissolving) the clot, blood thinners or more invasive techniques. Pulmonary embolism has been shown in the research to be one of the most common causes of death after bariatric surgery, so it’s very important to get up and walk and exercise after the surgery to avoid getting clots!

Bowel Obstruction from Scar

Bowel obstructions can form due to adhesions (internal scar tissue) after surgery. There is less risk for developing this type of bowel obstruction with laparoscopic surgery, because there is so much less scar tissue from the laparoscopic technique. The treatment for internal scar tissue can range from resting in the hospital to undergoing surgery.

Incisional Hernia

Hernias that form along the incision are less common with laparoscopic, vs. open surgery. While occurring in less than 1% of patients after the laparoscopic gastric bypass, the incidence can be 15-20% after the open surgery. The treatment for incisional hernia is surgical repair.


It is very rare to require a blood transfusion during gastric bypass surgery. We do not recommend that patients donate blood prior to surgery.

The following are complications specific to Gastric Bypass Surgery:


A stricture, or narrowing of the attachment between the stomach and intestine, can form due to scar tissue. This condition generally occurs in fewer than 5% of gastric bypass patients, but it varies between surgeons. It usually occurs between the first and third post-operative month, although smokers are at an increased lifetime risk for developing a stricture. The treatment typically consists of “endoscopic dilation” where the patient is sedated and a scope is passed through the mouth to the stomach and used to dilate the connection back to normal size. This is an outpatient procedure. Antacids are given for a period of time after the surgery to decrease risk of forming a stricture.


A leak is an area, most commonly where bowel and stomach are connected with staples, that doesn’t seal as quickly as the rest of the connection. The national average for post-operative leaks with gastric bypass surgery is less than 1%. The treatment varies between antibiotics and an operation, depending on the severity of the leak.

Internal Hernia

An internal hernia can form when the bowel twists or blocks itself. Fewer than 5% of gastric bypass patients develop an internal hernia. Surgery is required to repair an internal hernia and the patient usually goes home the next day. 


Side Effects

The vast majority of patients have little or no problems at all after Gastric Bypass Surgery. Some patients experience side effects of: temporary nausea/vomiting (especially if they are sensitive to anesthesia), constipation, dumping syndrome (sensitivity to sugar and/or fat) and temporary hair thinning. All patients have increased sensitivity to alcohol, absorbing 4 times as much alcohol from a drink and becoming easily intoxicated.