Intestinal bypass is a bariatric surgery performed on patients with morbid obesity to create an irreversible weight loss, when implementing harsh restrictions on the diets have failed. Jejunocolic anastomosis was firstly employed. Nonetheless, it led to some unexpected complications such as severe electrolyte imbalance and liver failure. It was then modified to jejunoileal techniques. Viewed as a novel form of treatment for obesity, many intestinal bypass operations were carried out in the 1960s and 1980s. Significant weight loss was observed in patients, but this surgery also resulted in several complications, for instance, nutritional deficiencies and metabolic problems. Due to the presence of surgical alternatives and anti-obesity medications, intestinal bypass is now rarely used.
Anatomy of human digestive system In the human digestive system, the stomach is responsible for mechanical and chemical digestions. The small intestine is involved in both the absorption and digestion of nutrients, whereas the large intestine is responsible for the elimination of wastes (defecation). The small intestine consists of 3 parts: duodenum, jejunum and ileum. The duodenum is the first part of the small intestine and is connected to the stomach via the pyloric valve. The jejunum is the second and middle part of the small intestine. The ileum is the last part of the small intestine and is connected to the cecum, a part of the large intestine, via the ileocecal valve.
Types of intestinal bypass
Procedures of intestinal bypass surgery The intestinal bypass surgery, as the name suggests, anastomoses 14 inches of the proximal duodenum, the part of the small intestine closest to the stomach, to the 4 inches of the distal ileum, the part of the small intestine closest to large intestines. This creates a blind loop and bypasses nearly 85-90 % of the small intestine. As a corollary, the absorption of nutrients is greatly reduced, and thus lead to apparent weight reduction. There are four variations of intestinal bypass. They are jejunocolic bypass, end-to-side jejunoileal bypass, end-to-end jejunoileal bypass, and biliopancreatic diversion, respectively.
Jejunocolic bypass First performed in 1963, the jejunocolic bypass is regarded as the first type of intestinal bypass surgery. This surgery anastomoses the proximal duodenum to the transverse colon (a part of the large intestine). The surgery, nevertheless, turned out to be a huge failure as patients suffered from severe electrolyte imbalance and metabolic disturbance after it.
End-to-side jejunoileal bypass
This type of surgery was designed to overcome the shortcomings of jejunocolic bypass. First performed in 1969, it anastomoses the end of the proximal duodenum to the side of the distal ileum. However, owing to the possibility of reflux of ileal content to the blind loop, some surgeons doubted the effectiveness of this surgery.
End-to-end jejunoileal bypass
This type of surgery appeared at the same time as end-to-side jejunoileal bypass. Some surgeons regarded this as a better option than end-to-side jejunoileal bypass because it prevented the reflux of ileal content to the blind loop. In order to achieve this, the end of the proximal duodenum is anastomosed to the distal ileum. The blind loop is drained to the transverse colon. However, two studies revealed that both end-to-side and end-to-end jejunoileal bypass had similar weight loss effect.
Biliopancreatic diversion
First appeared in 1980, biliopancreatic diversion involves two parts: gastrectomy and intestinal bypass. Firstly, gastrectomy removes a large portion of the stomach. Reduction in stomach capacity decreases the appetite of patients. Secondly, intestinal bypass anastomoses the proximal duodenum and the distal ileum. This intestinal bypass is different from the above three bypasses in the way that the blind loop carrying bile and digestive enzymes will drain into the distal portion of the small intestine. With this technique, the absorption of nutrients, in particular, fat, can be reduced tremendously.
Mechanisms of weight reduction This surgery acts in the following ways to help patients reduce their body weight:
Induction of malabsorption Induction of malabsorption is the most prominent effect of the surgery. The small intestines are responsible for most of the absorption of nutrients. By bypassing a considerable length of the small intestines, this type of surgery greatly reduces the absorption capacity of the digestive system. Malabsorption is especially prominent in biliopancreatic diversion. Not only does it reduce the length of the small intestine for absorption, but it also drains the bile and digestive enzymes only to the distal ileum. Bile is essential for fat absorption, while digestive enzymes facilitate the intake of proteins. Draining them to only the distal ileum further reduces the efficiency of intestinal absorption, hence achieving the goal of weight reduction.
Conditioning of appetite If the patients take excessive food after the surgery, they will experience abdominal discomforts such as steatorrhea and abdominal pain, as patients' digestive system capacity has been reduced drastically.
Selection Criteria Intestinal bypass, in spite of its highly effectiveness in weight reduction, is a risky and irreversible. Thus, it requires rigorous assessment and selection before the surgery is carried out. The following are the normal selection criteria:
Overweight for more than 100 lbs. Readiness to accept the side effects and hence all the follow-up procedures. Evidence of failure in all previous attempts in weight reduction. Stable mental health status. Psychiatric evaluation showing the obese state. An absence of all types of endocrinopathies that are correctable. This surgery serves as the LAST approach to lose weight when all other weight-losing methods have failed and at the same time, morbid obesity remains a life-threatening problem. It is crucial for patients to understand all the pros and cons of this surgery, despite the weight loss they aimed for.
Health impacts Intestinal bypass surgery can lead to loss of weight effectively, but it can also lead to various complications that should not be neglected. About half of the patients who received this surgery need rehospitalization to manage the complications. The expected outcomes and possible risks of the intestinal bypass surgery are shown as follows:
Expected surgical outcomes
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