Algorithm 41-6. Algorithm for management of abdominal pain months or years after Roux-en-Y reconstruction.

The choice of bariatric operation is a complex decision. Gastric bypass is considered the gold-standard

operation by many, although sleeve gastrectomy may soon supplant gastric bypass in this regard. The

high failure rate of gastric band has led some to argue that it should be eliminated from the repertoire,

although this is debated. While highly individualized, clinical considerations guide choice of operation.

Gastric bypass is highly effective in ameliorating GERD; sleeve gastrectomy and gastric band, in

contrast, may exacerbate GERD. Gastric bypass may provide theoretical advantages in the treatment of

diabetes (discussed below), but sleeve gastrectomy and to a lesser extent gastric band are also highly

efficacious in this regard. Gastric bypass is associated with increased intestinal oxalate absorption and

hyperoxaluria, and sleeve gastrectomy or gastric band should therefore be considered in patients with a

history of oxalate nephrolithiasis. Patients with severe gastroparesis may benefit from gastric bypass

rather than sleeve gastrectomy or gastric band, although data in this subgroup are sparse, and gastric

bypass itself may rarely lead to gastroparesis. Gastric band should be avoided in patients with dysphagia

or esophageal motility disorders. Sleeve gastrectomy and gastric band avoid the need for manipulation

of the small intestine and thus may be good choices in patients with complex abdominal surgical

histories. Despite its high late morbidity and long-term failure rates, gastric band remains an option for

risk-averse patients who are unaccepting of the relatively higher risk of perioperative morbidity and

mortality associated with gastric bypass and sleeve gastrectomy.

Preoperative preparation includes thorough medical, psychological, and dietary evaluations. Patients

should undergo age-appropriate cancer screening, and treatment for active medical issues should be

optimized. Sleep apnea testing should be performed in most if not all patients, as the prevalence of

sleep apnea in the obese population may exceed 70%, and appropriate treatment with continuous

positive airway pressure (CPAP) should be instituted prior to surgery and continued through the

perioperative period. Diabetes should be well controlled; while data do not support a specific value, a

preoperative HbA1c <8 is a common target. Some degree of preoperative surgeon–supervised dietinduced weight loss should be achieved in most patients, as data suggest that this practice reduces

hepatic steatosis, may reduce perioperative complications, and may be associated with improved longterm outcomes. Preoperative testing and treatment for Helicobacter pylori is recommended, although

data suggesting that this practice decreases postoperative anastomotic ulcer risk is equivocal.

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Operative Considerations

A thorough discussion of the technical aspects of bariatric surgery is beyond the scope of this chapter,

but a few important issues warrant mention. Obesity is a risk factor for DVT, and aggressive DVT

prophylaxis should be employed. Optimal prophylaxis agents and regimens have not been determined,

but unfractionated or low–molecular-weight heparin during operation and continued through the

hospitalization period is typical. Subtherapeutic dosing of these agents is common in the obese, and the

American College of Chest Physicians recommends weight-based dosing.

Table 46-4 Select Micronutrient Deficiencies Associated with Bariatric Surgery

Hand-sewn, linear stapler, and circular stapler techniques are used to create the gastrojejunostomy in

gastric bypass. No single technique demonstrates a clear advantage, although stenosis rates may be

higher with the circular stapler technique. Absorbable suture should be used for all anastomoses, as

1199

nonabsorbable suture is a nidus for ulcer formation. Routine intraoperative testing of the gastrojejunal

anastomosis with EGD-air insufflation or methylene blue instillation may be associated with reduced

anastomotic dehiscence rates and is advisable. The use of drains at the gastrojejunal anastomosis is

practiced selectively, and no clear data demonstrate that routine drain placement aids in early detection

or reduced morbidity of anastomotic dehiscence. Some data suggest that drains may allow for

nonoperative management of such events. Routine closure of internal hernia defects during gastric

bypass is controversial, as data do not clearly demonstrate that this practice reduces late hernia

incidence. Nonetheless, closure is straightforward, entails low morbidity, and is therefore

recommended. Risk–benefit analyses do not support prophylactic cholecystectomy during laparoscopic

bariatric surgery in the absence of cholelithiasis, or in the presence of asymptomatic cholelithiasis. It is

therefore reasonable to manage cholelithiasis in bariatric surgery patients as in all patients, that is,

perform cholecystectomy only if symptoms are present.

As with any laparoscopic operation, conversion to laparotomy is a reasonable option if laparoscopy

presents insurmountable technical challenges. That said, bariatric surgeons are well aware that “open”

bariatric surgery is not “easier” than laparoscopic surgery, but simply presents qualitatively different

technical challenges. Often, hepatomegaly is a major obstacle. Left hepatic lobe size should be assessed

at the beginning of every operation, and if adequate liver retraction is not possible, consideration

should be given to aborting the planned procedure, especially if significant steatosis is present that

might be mitigated by further preoperative diet-induced weight loss.

Perioperative and Postoperative Management

Perioperative care of the bariatric surgery patient is similar to that of any patient undergoing complex

GI surgery but must be tailored to the obese. Inpatient, outpatient, and operating room facilities should

be equipped with beds, chairs, lifting and transfer apparatuses, and other equipment capable of bearing

the weight of obese patients. Anesthesia, nursing, dietician, physical therapy, and other subspecialty

staff with experience in the management of obese patients are necessary. Hospital stays after

laparoscopic gastric bypass and sleeve gastrectomy are typically 1 to 3 days, while gastric band is

generally performed on an outpatient basis.

The dietary regimen in the first few weeks after surgery is designed to prevent food impaction at an

edematous surgical site and maintain adequate hydration, and includes clear liquids progressing to soft

foods. Caloric intake in the early postoperative period may be less than 500 cal/day, which is

acceptable as long as hydration is maintained. Within 2 to 3 weeks of surgery, solid foods may be

introduced and caloric intake will slowly rise, with a long-term maintenance target of 1,200 to 1,500

calories and 50 to 70 g of protein per day. Within a few months of surgery, most patients are able to eat

any foods in small quantities with few exceptions. Deviation from this pattern should raise concerns for

anastomotic stenosis, ulcer, or other complications. Persistent vomiting, unless clearly associated with a

specific food that when eliminated ameliorates symptoms, is abnormal and should prompt a diagnostic

workup, usually with UGI and/or EGD.

The incidence of cholelithiasis after bariatric surgery ranges from 15% to over 70%, but only

approximately 7% of patients will require cholecystectomy. Prophylactic treatment with

ursodeoxycholic acid reduces the risk of postoperative cholelithiasis, from 28% to 9% in one recent

meta-analysis. Such therapy entails little morbidity and a 6-month postoperative treatment regimen is

common practice. Data are equivocal, however, regarding whether this practice reduces

cholecystectomy rates or is cost-effective.

The variability in surveillance practices makes accurate estimation of the incidence of postoperative

nutritional deficiencies challenging, and a wide range of supplementation practices exist. Interpretation

of the data is made more difficult because obese patients are at high risk for pre-existing micronutrient

deficiencies independent of surgery. Vitamin D and zinc deficiencies, for example, afflict over 50% and

30% of obese patients, respectively. Abnormal serum levels of micronutrients after surgery are

common, ranging from 10% to >80% depending on the micronutrient, operation, and patient

population studied; clinically symptomatic deficiencies are less common. Consensus guidelines from the

American Association of Clinical Endocrinologists, the Obesity Society, and the ASMBS recommend that

gastric bypass patients undergo annual surveillance of 25-hydroxyvitamin D, calcium, iron, and B12

levels, along with a complete blood count, electrolyte and lipid panels, and liver function tests and

periodic bone scans, and receive lifelong daily multivitamin (including folate), calcium citrate, vitamin

D, and vitamin B12 supplementation, with iron supplementation in menstruating women.28 Sleeve

gastrectomy patients likely have a lower risk of nutritional deficiencies, but similar regimens are

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recommended. Gastric band patients receive a daily multivitamin, calcium, and vitamin D

supplementation.

Clinical follow-up after bariatric surgery should be lifelong. Primary care providers play a critical role

in preoperative and postoperative care. Endocrinology expertise may be required, especially in the early

postoperative period when diabetes may resolve rapidly. A medical bariatrician subspecialty is evolving

to care for this expanding patient population.

Physiologic Mechanisms Underlying Bariatric Surgery Efficacy

Restriction of caloric intake and nutrient malabsorption are the classic presumed mechanisms of

bariatric operations. These mechanisms are important, but their relationship to outcome is complex and

nonlinear. For example, data are conflicting regarding the correlation between gastric bypass pouch size

and weight loss. In general, pouch volumes <50 cc are associated with good results with little evidence

that smaller pouches achieve greater weight loss, while efficacy may decrease substantially as pouch

sizes increase beyond 50 cc. Similarly, common channel length teeters on a less well-defined threshold,

above which weight loss is poor and below which malnutrition results. Other features of restriction are

counterintuitive: more rapid gastric pouch emptying on oral contrast studies is associated with greater

weight loss after gastric bypass while sleeve gastrectomy is associated with increased gastric emptying

rates compared to native anatomy. These observations suggest a complex relationship between weight

regulation, metabolism, and gut anatomy and motility.

7 Complex mechanisms in addition to restriction and malabsorption contribute to weight loss and

improved metabolism after surgery, with qualitatively different responses than those associated with

diet-induced weight loss. Satiety is increased, hunger decreased, and metabolic rate increased after

bariatric surgery, the opposite of responses observed with diet-induced weight loss. Bariatric surgery

somehow “sidesteps” the normal compensatory responses that act to defend body weight with

nonsurgical weight loss. The mechanisms underlying these counterintuitive responses are not well

established. Among putative mechanisms are changes in gut hormone secretion secondary to altered

intestinal anatomy. Decades ago, it was observed that an oral glucose load elicits a greater insulin

response than an intravenous glucose load, leading to postulation of the existence of incretins, gut

hormones secreted in response to a meal that regulate systemic glucose metabolism. Subsequent

research led to the discovery of GIP and GLP-1, incretins secreted by duodenal K cells and ileal L cells,

respectively, in response to nutrient delivery to the small intestine. Incretins have diverse effects on

glucose homeostasis, potentiating central insulin secretion and peripheral insulin sensitivity. Alterations

in incretin hormone secretion secondary to gut anatomic derangements were invoked to explain the

observation that diabetes often improved within days of gastric bypass, well before substantial weight

loss.

The foregut and hindgut hypotheses have been proposed to explain this phenomenon: bypass of the

alimentary stream from the stomach, duodenum, and proximal jejunum (the foregut hypothesis), and

increased caloric delivery to the distal jejunum and ileum (the hindgut hypothesis) alter secretion of gut

hormones with improvement in glucose homeostasis. While data are less compelling for GIP and other

putative foregut hormones, evidence supports the hindgut hypothesis, including data demonstrating

increased serum GLP-1 levels after gastric bypass. While debate persists regarding the magnitude of

these effects on diabetes remission after gastric bypass, an understanding of incretin physiology has led

to the development of GLP-1 agonists as pharmacologic therapy for diabetes independent of bariatric

surgery.

Gut anatomic derangements mediate additional metabolic changes. Gastric bypass and sleeve

gastrectomy reduce secretion of the orexigenic hormone ghrelin from the gastric fundus, which may

reduce hunger after surgery. Gastric bypass and sleeve gastrectomy are associated with increased

secretion of peptide YY and oxyntomodulin, gut hormones secreted by L cells in parallel with GLP-1 in

response to a meal that induce satiety and inhibit gut motility and are central mediators of the “ileal

brake” mechanism. Roux-en-Y anatomy alters bile acid metabolism, increasing serum levels of

conjugated bile acids with beneficial effects on glucose and lipid metabolism. Bariatric surgery disrupts

vagal and enteroenteric innervations of the gut and alters CNS satiety responses. Finally, gastric bypass

is associated with alterations in gut microbiota that contribute to weight loss and resolution of

metabolic disease. The precise mechanisms by which these diverse effects contribute to weight loss and

metabolic disease remission remain unclear.

Mechanisms other than restriction and malabsorption underlie the systemic effects of bariatric

surgery. An emerging field of metabolic surgery is exploring operations designed to mimic the metabolic

effects of gastric bypass (e.g., ileal transposition, foregut exclusion) in animals and lean diabetic humans

1201

with promising results. Also in development are endoscopic and laparoscopic gastric plications,

intragastric balloon placement, vagal nerve blockade, gastric simulators, and impermeable intraluminal

duodenal and jejunal stents designed to prevent caloric absorption. Bariatric surgery in the 21st century

will evolve to include a broad array of procedures applied to a diverse patient population as these

efforts mature.

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