Intestinal bypass is a bariatric surgery performed in patients with morbid obesity to create irreversible weight loss when strict dietary restrictions are applied. The jejunocolic anastomosis was used first. Yet it led to some unexpected complications such as severe electrolyte imbalance and liver failure. It was later transformed into jejunoileal techniques. Many intestinal bypass surgeries were performed in the 1960s and 1980s, seen as a new form of treatment for obesity. Significant weight loss was observed in the patients, but this surgery also resulted in various complications such as nutritional deficiencies and metabolic problems. Due to the availability of surgical alternatives and obesity prevention drugs, bowel bypass is rarely used anymore.
In the human digestive system, the stomach is responsible for mechanical and chemical digestion. The small intestine takes care of both absorption and digestion of nutrients, while the large intestine is responsible for the removal of waste (defecation). It consists of 3 parts: small intestine, duodenum, jejunum and ileum. The duodenum is the first part of the small intestine and is connected to the stomach via the pyloric valve. 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, which is part of the large intestine, via the ileocecal valve.
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 4 inches of the distal ileum, the part of the small intestine closest to the large intestine. This creates a blind loop and bypasses approximately 85-90% of the small intestine. As a result, the absorption of nutrients is greatly reduced, leading to a significant weight reduction.
There are four types of intestinal bypass. These are jejunocolic bypass, end-to-side jejunoileal bypass, end-to-end jejunoileal bypass, and biliopancreatic surgery, respectively.
The jejunocolic bypass, first performed in 1963, is considered the first type of bowel bypass surgery. This surgery anastomoses the proximal duodenum to the transverse colon (part of the large intestine). Still, the surgery was a major failure as patients suffered from severe electrolyte imbalance and subsequent metabolic disturbance.
End-to-Side Jejunoileal Bypass
This type of surgery is designed to overcome the shortcomings of jejunocolic bypass. First made in 1969, it anastomoses the tip of the proximal duodenum to the distal ileum side. However, due to the possibility of reflux of the ileal contents into the blind ring, some surgeons doubted the effectiveness of this surgery.
End-to-End Jejunoileal Bypass
This type of surgery emerged at the same time as an end-to-end jejunoileal bypass. Some surgeons saw this as a better option than end-to-end jejunoileal bypass as it prevents the backflow of ileal contents into the blind loop. To achieve this, the tip of the proximal duodenum is anastomosed to the distal ileum. The blind ring is drained into the transverse column. However, two studies revealed that both end-to-end and end-to-end jejunoileal bypass had similar weight loss effects.
Biliopancreatic diversion, which first appeared in 1980, consists of two parts: gastrectomy and intestinal bypass. First of all, gastrectomy removes a large part of the stomach. The decrease in stomach capacity reduces the appetite of the patients. Second, intestinal bypass anastomoses the proximal duodenum and distal ileum. This intestinal bypass differs from the above three bypasses in that the blind ring carrying bile and digestive enzymes flows into the distal part of the small intestine. With this technique, the absorption of nutrients, especially fat, can be greatly reduced.
This surgery works in the following ways to help patients reduce their body weight:
Induction of malabsorption is the most prominent effect of the surgery. The small intestine is responsible for most of the absorption of nutrients. This type of surgery greatly reduces the absorption capacity of the digestive system, bypassing a considerable length of the small intestine.
Malabsorption is particularly pronounced in biliopancreatic diversion. Not only does it reduce the length of the small intestine for absorption, it also drains bile and digestive enzymes into the distal ileum only. While bile is essential for fat absorption, digestive enzymes facilitate protein intake. Emptying these into the distal ileum further reduces the efficiency of intestinal absorption, achieving the weight loss goal.
If patients take excessive food after surgery, they will experience abdominal discomfort such as steatorrhea and abdominal pain as the digestive system capacity of the patients is greatly reduced.
Nutritional deficiencies are frequently observed in patients after surgery due to malabsorption. They include:
Anorexia is considered a normal response found after the first few weeks of surgery, but after four to six weeks, most patients regain their initial appetite before undergoing surgery.
Hypokalemia is also considered a normal response after bowel bypass surgery. Without potassium supplements, almost all patients experience hypokalaemia. For this reason, patients are usually prescribed postoperative six-month tablets or liquid potassium supplements.
Some patients also have hypocalcemia. Symptoms from this electrolyte imbalance include anxiety, muscle cramps, and paresthesia. Calcium supplements are administered to patients when serum calcium levels are lower than normal.
Low serum levels of vitamin B12, vitamin A, vitamin D, vitamin E, and vitamin K are common post-surgery nutritional deficiencies. 1000 mg of Vitamin B12 per month is recommended, and vitamin and mineral supplements are also recommended from the first half of the surgery to the full year until the rapid weight loss period passes.
Damage to Organs
Liver damage is caused by a deficiency in nutritional supply and steatosis, where it remains the most serious and possibly fatal side effect. Patients may experience symptoms such as nausea and vomiting. Alcohol intake is unbearable as it increases the tendency for liver malfunction. Deaths due to liver failure have also been reported. By applying an amino acid oral replacement after surgery, these liver problems can be prevented.
Instead of performing bowel bypass surgery due to the mentioned complications, gastric bypass surgery is a more commonly used bariatric surgery today. Intestinal bypass surgery causes malabsorption by anastomosing the proximal and distal small intestine. Nevertheless, the small intestine has an important role in performing a wide variety of important physiological and metabolic functions such as the metabolism of lipids. In contrast, the stomach has a less important role in physiological and metabolic functions. The most obvious physiological function of the stomach is digestion, but the small intestine is also capable of digestion. Thus, gastric bypass surgery causes less damage to the general metabolism of foods. Gastric bypass causes weight loss by controlling the appetite of patients rather than causing malabsorption. As a result, intestinal bypass has now been replaced by gastric bypass.
Anti-obesity drugs are also a possible solution. Among the examples of such drugs, Orlistat, which was first prescribed in 2009, 1998, was an over-the-counter substance after obtaining approval from the European Medicines Agency. In clinical studies, patients prescribed with Orlistat (120 mg) showed better weight loss in one year (5.81 kg versus 8.76 kg). With effective medications, the obese can better control their weight without the need for a relatively high-risk surgery.
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