Pathophysiology of Sleeve Gastrectomy

Sleeve gastrectomy (SG), or longitudinal gastric resection, consists in a resection of the greater curvature of the stomach. In bariatric surgery, it was introduced by Hess in 1988 and by Marceau in 1990 as a component of the biliopancreatic diversion with duodenal switch (BPD/DS). Resecting the greater curvature of the stomach was aimed at reducing the risk of ulcer at the level of the duodeno-ileal anastomosis of the BPD/ DS. In fact, for those authors, the amount of stomach removed was estimated to be roughly 60% and the restriction was moderate. With a view to reducing the mortality associated with laparoscopic BPS/DS in super-super-obese patients, Regan et al. described a 60-French (F) bougiecalibrated isolated sleeve gastrectomy (ISG) as a first step in a two-stage program of laparoscopic BPD/DS in 2000. Since then, primary ISG has gained popularity in a staged surgery program for high-risk patients. Although medium- to long-term results are not known, and some technical details are still being discussed, the good short-term results obtained regarding weight loss, as well as co-morbidity and the acceptable rate of complications, have broadened the indications for primary ISG and assured its place in the armamentarium of bariatric surgical procedures. In June 2007, a position statement on SG as a bariatric procedure was endorsed by the ASMBS, and in October 2007 the First International Consensus Summit for Sleeve Gastrectomy was held in New York City. 

As expected, the operation is restrictive (satiety occurs very quickly). Indeed, with the current calibration of the sleeve, its volume is less than 10% of the entire stomach and its distensibility is 10 times less than that of the resected stomach and fundus. Nevertheless, after 6 months, patients can cope with a mug-sized meal (200 ml) of solid food. Even if the size of the meal is small, the volume of the remaining stomach is larger by far than after purely restrictive procedures (gastric banding, vertical banded gastroplasty). Melissas et al. demonstrated an accelerated gastric emptying of solid food into the duodenum and the intestine at 6 and 24 months, and this could explain some enterohormonal changes . In addition to these mechanical effects, SG has hormonal effects. This operation is “anorexigenic”; the patients feel little hunger and have only a mild interest in eating. Most of them could skip a meal each day for at least 1 year after surgery. The fundus is known to be the major source of ghrelin, an orexigenic hormone. It has been proved that the level of ghrelin is dramatically reduced after the currently performed SG with the entire fundus resected, and to a higher degree than with gastric banding or gastric bypass. Other hormonal changes have been noted, such as a rise in the level of fasting PYY or GLP1, a hormone that induces also a feeling of satiety. This latter point has yet to be assessed in human beings. These incretin modifications could play a role in the remarkable short-term effects observed on diabetes. Thus it appears that LSG is a multifactorial procedure with a mild restrictive aspect and a complex neurohormonal aspect.

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