Laparoscopic Gastric Bypass
Gastric Bypass Procedures (GBP) are a group of similar operations that first divides the stomach into a small upper pouch and a much larger lower “remnant” pouch and then re-arranges the small intestine so it connects to both. Any GBP leads to a marked reduction in the functional volume of the stomach, accompanied by an altered physiological and physical response to food.
A Gastric Bypass reduces the size of the stomach by well over 90%. A normal stomach can stretch, sometimes to over 1000 mL, while the pouch of the gastric bypass may be 15 mL in size.
A small stomach pouch is created to restrict food intake. Next, a Y-shaped section of the small intestine is attached to the pouch to allow food to bypass the lower stomach, the duodenum (the first segment of the small intestine), and the first portion of the jejunum (the second segment of the small intestine). This bypass reduces the absorption of nutrients, reducing calorie intake and restricting the volume of food that can be eaten.
The gastric bypass procedure consists of:
- Creation of a small (15–30 mL/1–2 tbsp) thumb-sized pouch from the upper stomach, accompanied by bypass of the remaining stomach (about 400 mL and variable). This restricts the volume of food which can be eaten. The stomach may simply be partitioned (typically by the use of surgical staples), or it may be totally divided into two parts (also with staples). Total division is usually advocated to reduce the possibility that the two parts of the stomach will heal back together (“fistulize”) and negate the operation.
- Re-construction of the GI tract to enable drainage of both segments of the stomach. The particular technique used for this reconstruction produces several variants of the operation, differing in the lengths of small intestine used, the degree to which food absorption is affected, and the likelihood of adverse nutritional effects.
Gastric bypass is prescribed for people who are morbidly obese (BMI>40), who have been unable to achieve satisfactory and sustained weight loss by dietary efforts and suffer from comorbid conditions such as type 2 diabetes, hypertension and sleep apnoea.
The gastric bypass pouch is usually formed from the part of the stomach which is least susceptible to stretching. That, and its small original size, prevents any significant long-term change in pouch volume.
What does change over time is the size of the connection between the stomach and intestine and the ability of the small intestine to hold a greater volume of food. However, by that time, weight loss has occurred, and the increased capacity should serve to allow maintenance of a lower body weight.
Weight loss of 50–80% of excess body weight over 2 years is typical of most large series of gastric bypass operations reported. The medically more significant effects are a dramatic reduction in comorbid conditions:
- Hyperlipidemia is corrected in over 70% of patients.
- Essential hypertension is relieved in over 70% of patients, and medication requirements are usually reduced in the remainder.
- Obstructive sleep apnoea is markedly improved with weight loss and bariatric surgery may be curative for sleep apnoea. Snoring also improves in most patients.
- Type 2 diabetes is reversed in up to 90% of patients usually leading to a normal blood sugar without medication, sometimes within days of surgery.
- Gastroesophageal reflux disease is relieved in almost all patients
Venous thromboembolic disease signs such as leg swelling are typically alleviated.
- Lower back pain and joint pain are typically relieved or improved in nearly all patients.
A study in a large comparative series of patients showed an 89% reduction in mortality over the five years following surgery, compared to a non-surgically treated group of patients. Concurrently, most patients are able to enjoy greater participation in family and social activities.
- “Dumping syndrome” if sweets and chocolates taken
- Good operation for sweet eaters
- Long track record
- Tend to lose a little more weight than gastric band
- Increased risks
- Longer recovery time
- Staple line leak
- Minor late weight regain 10-20% after 2-5 yrs
- Nutritional/ mineral supplements required
As with all surgery, complications occur. A study from 2005–2006 revealed that 15% of patients experience complications as a result of gastric bypass, and 0.5% of patients died within six months of surgery due to complications.
Some of the risks involved with a gastric bypass are:
- Anastomotic leakage
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 (gastro-jejunostomy). There is a change in the drain fluid contents from serous (before the leak) to faecal/bilious (after the leak). Usually significant leaks need urgent re-operation. Sometimes a minor leakage can be treated with antibiotics only. It is usually safer to re-operate if an infection cannot be definitely controlled immediately.
- Anastomotic stricture
As the anastomosis heals, it forms scar tissue, which naturally tends to shrink (“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.
- Anastomotic ulcer
Ulceration of the anastomosis occurs in 1–16% of patients. Possible causes of such ulcers are:
- Restricted blood supply to the anastomosis (compared to the blood supply available to the original stomach)
- 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 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 a “sky is falling” type of anxiety. The person usually has to lie down, and could be very uncomfortable for 30–45 minutes. Diarrhoea may then follow.