Operations systematically performed to achieve weight loss first appeared in the early 1950s, initially as removal of long segments of small bowel, subsequently as bypass of even longer intestinal segments excluded from the nutrient stream but available for reattachment should the need arise (intestinal bypass; jejuno-ileal bypass). Stomach operations, pioneered by Edward E. Mason of Iowa in the 1960s, similarly evolved from gastric resection into gastric bypass, excluding a large portion of the stomach, attaching the remnant to a loop of small bowel (Figure 34.1). Mason was convinced that the mechanism of weight loss was mechanical restriction of intake through the small gastric remnant ('pouch'). Thus, he went on to develop a purely restrictive operation, gastroplasty, consisting of a stapled pouch with an externally banded conduit into the stomach proper. The small size of the pouch ( < 15 ml) and the small diameter of the outlet (9 mm) physically limit the amount of food that can be consumed during a single meal.
Gastric bypass provides greater weight loss, sustained for longer periods of time in a larger proportion of patients than does gastroplasty. This implies that gastric bypass functions through other mechanisms than restriction alone. Undigested nutrients
emptying from the small stomach pouch into the segment of small bowel (jejunum) evoke satiety signals via mechanoreceptors. Calorically dense liquid or soft food rapidly emptying into the small bowel causes weight loss through 'dumping', an aversive physiological response associated with release of vasoactive gastrointestinal peptides elicited by chemoreceptors, portal chemoreceptors and possibly potentiated by peptide receptors in the brain. Regardless of mechanism, gastric bypass achieves greater weight loss than purely restrictive gastric operations.
Variants of gastric bypass use longer limbs of bypassed small bowel (Figure 34.1) causing more maldigestion and adding malabsorption leading to greater weight loss, appropriate in heavier patients (those with BMI > 50). Predictably, these operations have greater potential for causing deficiencies. The first of these more aggressive gastrointestinal bypass operations, biliopancreatic diversion (BPD), was introduced in 1976 by Nicola Scopinaro of Genoa. In its original form it included resection of the stomach with diversion of digestive bile and pancreatic secretions to the terminal 50 cm of ileum. These more malabsorptive operations have been performed in a few centers worldwide, though the series have been fairly large. A recent modification of biliopancreatic bypass, maintaining the pylorus and a portion of the duodenum, called 'duodenal
switch' (Figure 34.2) seems to improve protein absorption and cause fewer side effects than the biliopancreatic bypass of Scopinaro (3,4). This improved side-effect profile, replicated in several centers, is leading to wider adoption of these types of operations, such that they can be considered to be a legitimate alternative in selected patients.
All types of surgery have been dramatically transformed during the last decade owing to the technical advances making possible the development of laparoscopic techniques. Insertion of tiny fiberoptic light sources and cameras into inflated body cavities for transmission of images to video screens allows insertion and operation of instruments through smaller incisions with less surgical trauma—aptly called 'minimally invasive' surgery.
These techniques are especially appropriate in obese patients who generally require large incisions for exposure. Because of their reduced hemodynamic and respiratory reserves, obese patients withstand trauma less well than their lean counterparts, which is why they are considered to be higher operative risks. This is one of many
factors that traditionally has led to underutilization of surgical services among the obese. Minimally invasive techniques, with their shorter recovery times and shorter periods of postoperative rehabilitation, have made operations safer for obese patients, thus expanding their access to surgery.
The first bariatric surgical procedure to capitalize on the minimally invasive approach was circumgas-tric adjustable banding. This is a truly restrictive procedure, originally developed for open surgery by Lubomyr Kuzmak of New Jersey around 1985. An inflatable Silastic ring is placed just below the esophagogastric junction and is attached via tubing to a subcutaneous injectable port (Figure 34.3). As the patient's eating behaviour changes and the gastric wall adapts, the functional inner diameter of the conduit may change. The adjustable band allows titration of the desirable degree of restriction.
Vertical banded gastroplasty and gastric bypass became feasible laparoscopically with the development of laparoscopic stapling instruments. As with all surgery, laparoscopic or open, there is a learning curve until technical mastery can be achieved, with its attendant reduced complication rate. As of the end of 2000, there are reports of series of patients who have undergone these laparoscopic stapling operations. None have the appropriate 5-or-more year period of observation in sufficient numbers of patients necessary to evaluate the efficacy of these approaches. However, it does appear as if the safety of performance of these operations via laparoscopy is at least equivalent to that of the open procedures.
Because of the high degree of safety of performance of laparoscopic adjustable gastric banding, with very quick postoperative return to full function, and the relative ease of completely reversing the operation because of the non-reactive nature of the Silastic implant (band + tubing), it is reasonable to expand the availability of this very effective method for achieving weight loss. Patients developing complications and unmanageable side effects of the gastric restriction would be candidates for reversal of the operation as would be patients with inadequate weight loss. Given the > 95% recidivism of obesity and its comorbities after reversal of any bariatric operation, such patients should be offered a malab-sorptive type of operation such as gastric bypass at the time of the reversal. Staged surgery appears to be a logical strategy in the overall management of severely obese patients (5).
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