Other
Sleeve gastrectomy — Sleeve gastrectomy is a newer technique offered to patients with super morbid obesity as the first stage in surgical management [51,52]. The procedure consists of a laparoscopic partial gastrectomy in which the majority of the greater curvature of the stomach is removed and a tubular stomach is created. The tubular stomach is small in its capacity (restriction), resistant to stretching due to absence of fundus, and devoid of ghrelin producing cells (a gut hormone involved in regulating food intake). (See "Pathogenesis of obesity"and see "Ghrelin").
Patients experience approximately 33 percent EWL in one year [52]. This allows surgeons to perform the less technically challenging partial gastrectomy first, delaying the more technically rigorous laparoscopic Roux-en-Y gastric bypass or BPD until after the patients have reached a lower weight [52]. Sleeve gastrectomy has also been used as an isolated initial bariatric procedure, particularly in high-risk patients [53].
Intragastric balloon — The intragastric balloon (Bioenterics Intragastric Balloon, Inamed) is a temporary alternative for weight loss in moderately obese individuals [54-57]. It consists of a soft, saline-filled balloon placed endoscopically that promotes a feeling of satiety and restriction. It is currently not available for use in the United States, but is undergoing extensive testing in Europe and Brazil. Mean excess weight loss is reported to be 38 percent and 48 percent for 500 and 600 mL balloons, respectively [55]. However, the results of a Brazilian multi-center study indicate weight loss is transient, with only 26 percent of patients maintaining over 90 percent of the excess weight loss out over one year [56]. It appears to reduce the risk of conversion to open surgery and the risk of intraoperative complications when it is used for preoperative weight loss in super-obese patients before a definitive bariatric procedure [57]. Side-effects include nausea, vomiting, abdominal pain, ulceration, and balloon migration.
MALABSORPTIVE
Jejunoileal bypass — The jejunoileal bypass was one of the first bariatric operations, performed initially in 1969 [58]. It has since been abandoned due to the high complication rate and frequent need for revisional surgery. Its importance lies in care of surviving patients who have undergone this procedure.
The procedure was performed by dividing the jejunum close to the ligament of Treitz and connecting it a short distance proximal to the ileocecal valve (show figure 3), thereby diverting a long segment of small bowel, resulting in malabsorption. Although excess weight loss was excellent, jejunoileal bypass was associated with multiple complications such as liver failure (up to 30 percent), death, diarrhea, electrolyte imbalances, oxalate renal stones, vitamin deficiencies, malnutrition, and arthritis [59-63].
Biliopancreatic diversion — The biliopancreatic diversion (BPD) was introduced as a solution to the high rates of liver failure resulting from bowel exclusion in the jejunoileal bypass [64] (show figure 4). The procedure consists of a partial gastrectomy and gastroileostomy with a long segment of Roux limb and a short common channel (the part of the small bowel that receives both food and biliopancreatic secretions) resulting in malnutrition. Up to 72 percent excess weight loss up to 18 years have been reported. Laparoscopic BPD has also been performed with acceptable outcomes [65]. Its use has been limited by the high rates of protein malnutrition, anemia, diarrhea, and stomal ulceration [66].
Biliopancreatic diversion with duodenal switch — The biliopancreatic diversion with duodenal switch (BPD/DS) is a variant of the BPD, and is primarily a malabsorptive operation [67] (show figure 5). The procedure involves a partial sleeve gastrectomy, preserving the pylorus, as well as creation of a Roux limb with a short common channel. The BPD/DS procedure differs from the BPD in the portion of the stomach that is removed, as well as preservation of the pylorus [66,67].
Although complex, BPD/DS has been performed laparoscopically by several groups [68,69]. This procedure is performed at a few centers in the United States, whose proponents feel it achieves sustainable weight loss with a lower incidence of stomal ulceration and diarrhea than those seen in BPD alone. It has been advocated for patients with super-morbid obesity (BMI >50). At present, it is not widely accepted as the first-line surgical treatment for morbid obesity in the United States, partly due to inconsistent recognition and reimbursement for this procedure by the insurance companies.
MIXED
Roux-en-Y gastric bypass — Roux-en-Y gastric bypass (RYGB) was developed in the 1960s based on the observation that patients who underwent partial gastrectomy experienced significant long-term weight loss [70]. Many subsequent modifications have been made to improve the weight loss outcome and limit operative complications. It is the most common bariatric procedure performed in the United States and is considered the **** standard among bariatric procedures.
While the RYGB is primarily a restrictive operation, a malabsorptive component also contributes to weight loss. RYGB has been shown repeatedly to be better than purely-restrictive procedures such as Vertical Banded Gastroplasty (VBG) in long-term weight reduction [31].
Its current configuration is characterized by a small (less than 30 mL) proximal gastric pouch divided and separated from the stomach remnant with drainage of food to the rest of the gastrointestinal tract via a tight stoma and a Roux-en-Y small bowel arrangement (show figure 6). The small pouch and the tight outlet act to restrict caloric intake, as seen in VBG and LAGB. A much larger gastric remnant becomes disconnected from the food stream while secretion of gastric acid, pepsin, and intrinsic factor continues.
The small intestine is then divided at a distance of 30 to 50 cm distal to the Ligament of Treitz. By dividing the bowel, the surgeon creates a proximal biliopancreatic limb that transports the secretions from the gastric remnant, liver, and pancreas. The Roux limb (or alimentary limb) is anastomosed to the new gastric pouch and functions to drain consumed food. The cut ends of the biliopancreatic limb and the Roux limb are then connected approximately 75 to 150 cm distally from the gastrojejunostomy. Major digestion and absorption of nutrients then occurs in the common channel where pancreatic enzymes and bile mix with ingested food.
Weight loss following gastric bypass is mostly attributed to restriction, but other mechanisms such as dumping syndrome, Roux limb length, and gut hormones may have a role in the weight loss seen following gastric bypass.
Gastrojejunostomy anatomy (connection between the stomach pouch and jejunum) is associated with dumping physiology, and causes unpleasant symptoms of light-headedness, nausea, diaphoresis and/or abdominal pain, and diarrhea when a high sugar meal is ingested [71]. This response may serve as a negative conditioning response against consumption of high sugar diet postoperatively.
The optimal length of the Roux limb in achieving the best balance between weight reduction and complications of malabsorption is controversial. Increasing Roux limb length can lead to increased malabsorption, since lengthening the Roux limb effectively shortens the common limb where major digestion and absorption of the ingested nutrients occur. At present, most surgeons do not make the Roux length longer than 100 cm. Distal gastric bypass with a short common limb has been used to treat patients with inadequate weight loss following standard RYGB, but the risk for metabolic complications increase similar to other malabsorptive operations [72].
Ghrelin is a peptide hormone secreted in the foregut (stomach and duodenum) that stimulates the early phase of meal consumption. The normal pulsatile release of this orexigenic (appetite-producing) hormone appears to be inhibited in gastric bypass patients due to its unique foregut bypass configuration [73-75]. Such inhibition of ghrelin has not been observed in other bariatric procedures [74]. This may contribute to the characteristic loss of appetite seen in post RYGB patients. An exaggerated response of peptide YY (PYY) may also contribute to the loss of appetite [75]. (See "Pathogenesis of obesity"and see "Ghrelin").
RYGB can be safely performed laparoscopically in well-trained hands. Despite its steep learning curve [76], laparoscopic RYGB provides several advantages such as lower incidence of incisional hernia, wound infection, faster recovery, and a shorter hospital stay [77-79]. Although the procedure can be limited by patient size, instrument and trocar length, even the extremely large patients have been successfully operated laparoscopically in some series [80].
Excess weight loss after gastric bypass is durable and reliable. On average, 62 to 68 percent EWL is reported after the first year. Early weight loss following gastric bypass is typically rapid, but usually reaches a plateau after one to two years to an average EWL percent between 50 to 75 percent [77,78,81,82]. Sustained weight loss is seen up to 16 years [81], making this procedure an excellent tool for a permanent surgical weight loss. Improvement and/or resolution of comorbid conditions (including diabetes, sleep apnea, hypertension, and dyslipidemia) following gastric bypass has also been well-established [77,81-83].
23-08-2006, 06:00 AM
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