Treating severe obesity is often a Catch-22: the patient must begin exercising in order to start losing weight yet the excess weight can make exercise difficult (if not dangerous). To address this issue, surgeons have developed many procedures to drastically curb appetite or interfere with nutrient absorption, which reduces calorie intake enough to cause significant weight loss: adjustable gastric band (AGB), vertical sleeve gastrectomy (VSG), biliopancreatic diversion (BPD) and Roux-en-Y gastric bypass (RYGB). However, each procedure has its own set of risks and benefits; the key is to determine which one is best for the patient.
Adjustable Gastric Band (AGB)
The adjustable gastric band is a plastic cuff lined with inflatable balloons that fastens around the top portion of the stomach, effectively pinching the organ into two mini-pouches connected by a narrow passage (Figure 1). The cuff is attached to a flexible polyurethane tube that connects to an injection node outfitted with a special intake-outtake valve. Hypodermic needles containing saline (i.e. water with sodium chloride dissolved in it) can be pushed through the skin into the injection node to add or remove solution, causing the AGB to compress or expand the radius of the passage between the mini-pouches.
By pinching the stomach, food moves at a slower rate through the organ, causing the first mini-pouch to fill up quickly. Hence, the patient feels "full" after eating much less food than usual. Overtime, this reduction of food intake cuts calories and gives the rest of the stomach a chance to contract. By naturally contracting, the stomach will eventually require less food to achieve a "full" feeling. This opens the door to one day removing the AGB without risking that the patient will return to the unhealthy binging habits that caused his/her obesity in the first place.
Installing an AGB can usually be done laparoscopically with 4 small incisions, making it the least invasive weight loss surgery. AGB is best reserved for patients who, aside from being too overweight to safely begin an effective exercise regimen, are not suffering from life-threatening conditions caused by obesity (e.g., metabolic disorder, diabetes, extreme hypertension).
Roux-en-Y Gastric Bypass (RYGB)
Popularly known as "stomach stapling," RYGB is the most commonly administered surgery for weight loss. Doctors typically recommend RYGB when a patient's obesity either becomes disabling or actually causes a life-threatening condition like diabetes or heart disease.
This procedure takes AGB's mini-pouch strategy for appetite reduction and combines it with a surgical technique designed to limit the calories that the body absorbs from food. The surgeon places two clamps next to each other on a section of the small intestine, separates the small intestine by cutting between the clamps and then removes the connective membrane from roughly 16 inches of intestine to the right of the clamps.
Meanwhile, the surgeon places either surgical staples or a plastic clamp across the upper region of the stomach to form a small, thumb-sized pouch. At this point, a small incision is made in the pouch and the surgeon surtures the freed portion of the small intestine to it, resulting in an artificial gastro-intestinal (G.I.) tract that bypasses the lower stomach and feed directly into the center of the small intestine (Figure 2). The decreased stomach size curbs appetite while reducing the total area of the intestines dedicated to absorbing calories from food.
While very effective at reducing caloric intake and triggering massive weight-loss, RYGB comes with risks. The greatest danger is malnutrition or "dumping syndrome": a condition where food passes too quickly through the intestines, preventing the absorption of non-caloric vitamins and minerals needed for the nervous and vascular systems to function properly. Luckily, this can be prevented by avoiding processed sugar (i.e. sweets) and sticking to a strict multi-vitamin regimen.
Beyond dumping syndrome, the malabsorption of minerals like calcium and iron can cause osteoporosis and anemia, respectively, down the road.
Biliopancreatic Diversion With A Duodenal Switch (BPD-DS)
Usually referred to as "duodenal switch," BPD-DS is far more complex than other weight loss surgeries but also has more long-term health benefits. Rather than bypassing the stomach, the procedure simply removes a part of it. This reduces size while preserving important the pyloric sphincter, which slows food movement to prevent dumping syndrome. Like RYGB, the center of the small intestine is re-routed but, in BPD-DS, it is routed to the bottom opening of the stomach (Figure 3). Meanwhile, the end of the upper small intestine is re-routed to the bottom of the lower small intestine, allowing digestive enzymes secreted from the pancreas and liver to mix with food and promote better nutrient absorption.
BPD-DS is riskier than RYGB in the short term but has great long-term benefits; whether or not to use it is usually a matter of patient preference. BPD-DS involves multiple surgeries, each with the standard risk of infection or internal bleeding. However, patients with BPD-DS report easier digestion of natural foods, a lower incidence of malnutrition, fewer cases of osteoporosis, anemia and hernias in the intestinal walls.
Vertical Sleeve Gastrectomy (VSG)
VSG forgoes intestinal re-routing and simply reduces the size of the stomach by excising the "stretchable" portion (Figure 4). By keeping the pyloric sphincter intact, the prevents dumping syndrome while helping to control food intake by making the patient feel "full" more quickly. Excising the stomach tissue has another benefit as well: decreasing the amount of gherlin (a hormone secreted by stomach tissue to trigger a feeling of "hunger" in the brain).
The downside of VSG is that there is a danger of the stomach "re-stretching" over time, allowing for the weight be gained back. However, VSG is a very good option for patients with conditions that would make RYGB or BPD-DS surgeries riskier (e.g., taking anti-inflamatory medication or steroids for auto-immune conditions like Crohn's disease, arthritis or asthma).
Vagotomy (Still In Experimental Phase)
Historically used to treat the pain from stomach ulcers caused by antibiotic-resistant H. pylori, a vagotomy is the surgical removal of the vagus nerve. The vagus nerve runs from the stomach to the brain and is believed to play a major role in the way the mind perceives hunger.
Early clinical trials for vagotomy as a weight-loss treatment have showed patients to lose an average of 20 percent of their starting body weight. However, it will likely be years before vagotomy is officially recognized as a safe, effective treatment.
Tags: small intestine, dumping syndrome, weight loss, adjustable gastric band, caused obesity