Any major surgery involves the potential for complications—adverse events which increase risk, hospital stay, and mortality. Some complications are common to all abdominal operations, while some are specific to bariatric surgery.
Mortality and complication rates
The overall rate of complications during the 30 days following surgery ranges from 7% for laparoscopic procedures to 14.5% for operations through open incisions.
Mortality and complications are affected by pre-existing risk factors such as degree of obesity, heart disease, obstructive sleep apnea, diabetes mellitus, and history of prior pulmonary embolism. It is also affected by the experience of the operating surgeon: the learning curve for laparoscopic bariatric surgery is estimated to be about 100 cases. Supervision and experience is important when selecting a surgeon, as the way a surgeon becomes experienced in dealing with problems is by encountering and solving them.
Complications of abdominal surgery
Infection of the incisions or of the inside of the abdomen may occur due to release of bacteria from the bowel during the operation. Nosocomial infections, such as pneumonia, bladder or kidney infections, and blood-borne infection are also possible. Effective short-term use of antibiotics, diligent respiratory therapy, and encouragement of activity within a few hours after surgery can reduce the risks of infections.
Any injury, such as a surgical operation, causes the body to increase the coagulation of the blood. Simultaneously, activity may be reduced. There is an increased probability of formation of clots in the veins of the legs, or sometimes the pelvis, particularly in the morbidly obese patient. A clot which breaks free and floats to the lungs is called a pulmonary embolus, a very dangerous occurrence. Blood thinners are commonly administered before surgery to reduce the probability of this type of complication.
Many blood vessels must be cut in order to divide the stomach and to move the bowel. Any of these may later begin bleeding, either into the abdomen , or into the bowel itself. Transfusions may be needed, and re-operation is sometimes necessary. Use of blood thinners to prevent venous thromboembolic disease may actually increase the risk of hemorrhage slightly.
A hernia is an abnormal opening, either within the abdomen or through the abdominal wall muscles. An internal hernia may result from surgery and re-arrangement of the bowel, and is a cause of bowel obstruction. Antecolic antegastric Roux-en-Y gastric bypass surgery has been estimated to result in internal hernia in 0.2% of cases, mainly through Petersen’s defect. An incisional hernia occurs when a surgical incision does not heal well; the muscles of the abdomen separate and allow protrusion of a sac-like membrane, which may contain bowel or other abdominal contents, and which can be painful and unsightly. The risk of abdominal-wall hernia is markedly decreased in laparoscopic surgery.
Abdominal surgery always results in some scarring of the bowel, called adhesions. A hernia, either internal or through the abdominal wall, may also result. When the bowel becomes trapped by adhesions or a hernia, it may become kinked and obstructed, sometimes many years after the original procedure. An operation is usually necessary to correct this problem.
Complications of gastric bypass
An anastomosis is a surgical connection between the stomach and bowel, or between two parts of the bowel. The surgeon attempts to create a water-tight connection by connecting the two organs with either staples or sutures, either of which actually makes a hole in the bowel wall. The surgeon will rely on the body’s natural healing abilities and its ability to create a seal, like a self-sealing tire, to succeed with the surgery. If that seal fails to form for any reason, fluid from within the gastrointestinal tract can leak into the sterile abdominal cavity and give rise to infection and abscess formation. Leakage of an anastomosis can occur in about 2% of Roux-en-Y gastric bypass and less than 1% in mini gastric bypass. Leaks usually occur at the stomach-intestine connection.
As the anastomosis heals, it forms scar tissue, which naturally tends to “contract” over time, making the opening smaller. This is called a “stricture”. Usually, the passage of food through an anastomosis will keep it stretched open, but if the inflammation and healing process outpaces the stretching process, scarring may make the opening so small that even liquids can no longer pass through it. The solution is a procedure called gastroendoscopy, and stretching of the connection by inflating a balloon inside it. Sometimes this manipulation may have to be performed more than once to achieve lasting correction.
Ulceration of the anastomosis occurs in 1–16% of patients. Possible causes of such ulcers are:
- Restricted blood supply to the anastomosis.
- Anastomosis tension
- Gastric acid
- The bacteria Helicobacter pylori
- Use of non-steroidal anti-inflammatory drugs
This condition can be treated with:
- Proton pump inhibitors, e.g. esomeprazole
- A cytoprotectant and acid buffering agent, e.g. sucralfate
- Temporary restriction of the consumption of solid foods
Normally, the pyloric valve at the lower end of the stomach regulates the release of food into the bowel. When the gastric bypass patient eats a sugary food, the sugar passes rapidly into the intestine, where it gives rise to a physiological reaction called dumping syndrome. The body will flood the intestines with gastric content in an attempt to dilute the sugars. An affected person may feel their heart beating rapidly and forcefully, break into a cold sweat, get a feeling of butterflies in the stomach, and may have an anxiety attack. The person usually has to lie down, and could be very uncomfortable for 30–45 minutes. Diarrhea may then follow.
Nutritional deficiencies are common after gastric bypass surgery, and are often not recognized. They include:
Secondary hyperparathyroidism due to inadequate absorption of calcium may occur for GBP patients. Calcium is primarily absorbed in the duodenum, which is bypassed by the surgery. Most patients can achieve adequate calcium absorption by supplementation with vitamin D and calcium citrate-carbonate may not be absorbed—it requires an acidic stomach, which is bypassed.
Iron frequently is seriously deficient, particularly in menstruating females, and must be supplemented. Again, it is normally absorbed in the duodenum. Ferrous sulfate can cause considerable GI distress in normal doses; alternatives include ferrous fumarate, or a chelated form of iron. Occasionally, a female patient develops severe anemia, even with supplements, and must be treated with parenteral iron. The signs of iron deficiency include: brittle nails, an inflamed tongue, constipation, depression, headaches, fatigue, and mouth lesions.
Signs and symptoms of zinc deficiency may also occur such as: acne, eczema, white spots on the nails, hair loss, depression, amnesia, and lethargy.
Deficiency of thiamine (also known as vitamin B1) brings the risk of permanent neurological damage. Signs of thiamin deficiency are heart failure, memory loss, and numbness of the hands, constipation, and loss of appetite.
Vitamin B12 requires intrinsic factor from the gastric mucosa to be absorbed. In patients with a small gastric pouch, it may not be absorbed, even if supplemented orally, and deficiencies can result in pernicious anemia and neuropathies. Vitamin B12 deficiency is quite common after gastric bypass surgery with reported rates of 30% in some clinical trials. Sublingual B12 (cyanocobalamin) appears to be adequately absorbed. In cases where sublingual B12 does not provide sufficient amounts, injections may be needed.
Protein malnutrition is a real risk. Some patients suffer troublesome vomiting after surgery, until their GI tract adjusts to the changes, and cannot eat adequate amounts even with 6 meals a day. Many patients require protein supplementation during the early phases of rapid weight loss to prevent excessive loss of muscle mass. Hair loss is also a risk of protein malnutrition.
Vitamin A deficiencies generally occur as a result of fat-soluble vitamins deficiencies. This often comes after intestinal bypass procedures such as jejunoileal bypass or biliopancreatic diversion/duodenal switch procedures. In these procedures, fat absorption is markedly impaired. There is also the possibility of a vitamin A deficiency with use of the weight-loss medication orlistat .
Folate deficiency is also a common occurrence in gastric bypass surgery patients.