Principles of surgery

PART II
Specific Considerations

CHAPTER 27
The Surgical Management of Obesity

BASIC SCIENCE QUESTIONS

1. Which of the following has been directly implicated as a cause of obesity?

A. Lack of early childhood exposure to fruits and vegetables

B. Lack of early childhood exposure to exercise

C. Increased appetite and drive to eat

D. Decreased sensation of satiety

Answer: D

The increase in obesity is multifactorial. Genetics plays an important role in the development of obesity. Although the children of parents of normal weight have a 10% chance of becoming obese, the children of two obese parents have an 80 to 90% chance of developing obesity by adulthood. The weight of adopted children correlates strongly with the weight of their birth parents. Furthermore, concordance rates for obesity in monozygotic twins are double those in dizygotic twins.

Diet and culture are important factors as well. These environmental factors contribute significantly to the epidemic of obesity in the United States, because the rapid increase in obesity during the past two decades cannot be explained by any genetic cause. Other factors appear to contribute significantly to severe obesity.

Intermittent or consistent excessive caloric intake occurs. The lack of satiety, on a consistent or intermittent basis, appears to be strongly correlated with such episodes of excessive caloric ingestion. As yet the physiologic basis for such a lack of satiety is not understood.

Other factors commonly suggested to play a role in the disease of obesity include decreased energy expenditure from reduced metabolic activity, reduction in the thermogenic response to meals, an abnormally high set point for body weight, and a decrease in the loss of heat energy. Another factor that may influence absorption of ingested food is the composition of the intraluminal bacteria of the intestinal tract. Recent studies have documented a difference in the composition of the intestinal flora of obese individuals compared with those of normal weight. (See Schwartz 9th ed., p 951.)

2. Losing weight requires creating a calorie deficit. How much deficit is required to lose 1 pound weekly?

A. 1000 calories

B. 2250 calories

C. 3500 calories

D. 4200 calories

Answer: C

Lifestyle changes involving diet, exercise, and behavior modification constitute the first tier of therapy for obesity. Dietary restriction and exercise can each independently create a caloric deficit. A daily energy deficit so created of 500 kcal/d, resulting in a weekly deficit of 3500 kcal, results in the loss of 1 lb of fat weekly. It has been shown that low-calorie diets (800 to 1500 kcal/d) are as effective as very-low calorie diets at 1 year but result in a lower rate of nutritional deficiencies. Such diets may produce an average of 8% body weight loss over a 6-month period. Longer follow-up shows recidivism. Moderate daily physical activity can produce a 2 to 3% body weight loss. (See Schwartz 9th ed., p 952.)

CLINICAL QUESTIONS

1. A patient with a BMI of 38 is considered

A. Overweight

B. Obese

C. Severely obese

D. Superobese

Answer: C

(See Schwartz 9th ed., p 950, and Table 27-1.)

TABLE 27-1 Classification of obesity by body mass index (BMI)

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2. Which of the following is associated with or caused by obesity?

A. Cluster headaches

B. Pseudotumor cerebri

C. Liposarcoma

D. Fat embolism

Answer: B

Significant comorbidities, defined as medical problems associated with or caused by obesity, are numerous. The most prevalent and acknowledged of these include degenerative joint disease, low back pain, hypertension, obstructive sleep apnea, gastroesophageal reflux disease (GERD), cholelithiasis, type 2 diabetes, hyperlipidemia, hypercholesterolemia, asthma, hypoventilation syndrome of obesity, fatal cardiac arrhythmias, right-sided heart failure, migraine headaches, pseudotumor cerebri, venous stasis ulcers, deep vein thrombosis, fungal skin rashes, skin abscesses, stress urinary incontinence, infertility, dysmenorrhea, depression, abdominal wall hernias, and an increased incidence of various cancers such as those of the uterus, breast, colon, and prostate.

Although migraines are associated with morbid obesity, cluster headaches are not. Uterine, breast, colon, and prostate cancers have an increased incidence in patients with morbid obesity, and liposarcoma does not. Fat embolism, seen after fractures, is not more common in morbidly obese patients. (See Schwartz 9th ed., p 951.)

3. What percent of morbidly obese patients are able to successfully lose weight and maintain that weight loss by eating fewer calories and increasing the amount of exercise they do?

A. 5%

B. 5-10%

C. 10-15%

D. >15%

Answer: A

Medical treatment for severe obesity is aimed at reducing body weight through a combination of decreased caloric intake and accompanying increases in energy expenditure from moderate exercise. This method of weight loss is the safest possible and may work well for obese individuals who have modest amounts of weight to lose to regain normal body weight or to return to being simply overweight instead of obese. For the severely obese individual, however, who usually must lose at least 75 lb or more to achieve elimination of obesity, this is a daunting and extremely difficult task. The success rate among severely obese patients who try dieting and exercise as a means of losing enough weight to no longer be obese and maintaining that weight loss is only approximately 3%. (See Schwartz 9th ed., p 951.)

4. Which of the following drugs is approved by the FDA for weight loss?

A. Phentermine

B. Nuphedragen

C. Ambislim

D. Sibutramine

Answer: D

Currently there are only two drugs approved by the U.S. Food and Drug Administration for the treatment of obesity that promote weight loss. Sibutramine is a noradrenaline and 5-hydroxytryptamine reuptake inhibitor that works as an appetite suppressant. Orlistat inhibits gastric and pancreatic lipase enzymes that promote lipid absorption in the intestine. Either of these drugs may produce a weight loss of between 6 and 10% of body weight after 1 year, but cessation of the drug usually results in prompt regaining of lost weight.

Phentermine is an appetite suppressant, similar to amphetamines chemically. In combination with fenfluramine (Phen-Fen), it can cause pulmonary hypertension. Phentermine is not approved by the FDA. Nuphedragen is sold as a “fat burner.” There are no data on safety or efficacy and this is not approved by the FDA. Ambislim is an herbal mixture, also untested, that is not approved by the FDA. (See Schwartz 9th ed., p 952.)

5. A bilipancreatic diversion (BPD) with duodenal switch is primarily a

A. Restrictive procedure

B. Malabsorptive procedure

C. Combination restrictive and malabsorptive procedure

D. None of the above

Answer: C

The BPD is a combination restrictive and malabsorptive procedure. (See Schwartz 9th ed., p 953, and Table 27-2.)

TABLE 27-2 Types of commonly performed bariatric
operations by mechanism of action

Restrictive

Laparoscopic adjustable gastric banding (LAGB)

Sleeve gastrectomy (SG)

Vertical banded gastroplasty (VBG)a

Malabsorptive

Biliopancreatic diversion (BPD)

Jejunoileal bypass (JIB)a

Combined restrictive and malabsorptive

Roux-en-Y gastric bypass (RYGB)

BPD with duodenal switch (DS)

aNow rarely performed and of historic interest only.

6. Which of the following patients would be considered a candidate for bariatric surgery?

A. 70 year old, BMI 48, with well-controlled diabetes

B. 22 year old, BMI 34, with brittle (uncontrollable) diabetes

C. 35 year old, BMI 38, with no comorbidities

D. 56 year old, BMI 42, with no comorbidities

Answer: D

The indications for bariatric surgery have been clearly defined and are listed in Table 27-3. Of the patients listed above, only D is the correct answer. (See Schwartz 9th ed., p 954.)

TABLE 27-3 Indications for bariatric surgery

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7. Which group of patients has a poor outcome following placement of an adjustable gastric band?

A. Overweight

B. Obese

C. Morbidly obese

D. Superobese

Answer: D

Superobese patients have less weight loss than the obese or morbidly obese patients undergoing placement of an adjustable gastric band. Overweight people are not candidates for any bariatric procedure.

Efficacy of the operation in the superobese (body mass index (BMI) >50 kg/m2) is less impressive, with average BMI remaining >40 kg/m2 after 5- to 8-year follow-up. It has been our impression that optimal results occur with this operation in patients who are motivated, need to lose 50 kg to achieve a BMI of 30 kg/m2, are willing and able to exercise regularly, are amenable to changing eating patterns as recommended, and live within a geographic area close enough for easy follow-up. Patients who are impatient to lose weight, are immobile, are unable to exercise, are confirmed ‘grazers’ or nibblers on high-calorie sweets, and expect to be able to continue their dietary habits without great alteration are not good candidates for this operation. Similarly, patients who have had previous upper gastric surgery, such as a Nissen fundoplication, are relatively poor candidates for laparoscopic adjustable gastric banding (LAGB) due to the potential tissue compromise in taking down the wrap to place the band. (See Schwartz 9th ed., p 959.)

8. Which of the following procedures has the highest rate of nutritional complications?

A. Laparoscopic adjustable banding

B. Roux-en-Y gastric bypass

C. Sleeve gastrectomy

D. Duodenal switch

Answer: D

The duodenal switch, also called the biliopancreatic diversion with duodenal switch, has the highest rate of nutritional complications. (See Schwartz 9th ed., pp 961; 968, and Table 27-4.)

TABLE 27-4 Outcomes for bariatric operations

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9. Which of the following is the most common emergent complication of laparoscopic adjustable gastric bands?

A. Band slippage

B. Dysfunction or leak from the reservoir or tubing

C. Prolapse

D. Erosion

Answer: C

Prolapse is perhaps the most common emergent complication that requires reoperation after laparoscopic adjustable gastric banding (LAGB). The incidence is generally in the 3% range. Postoperative vomiting predisposes to this problem, because the lower stomach can be pushed upward and trapped within the lumen of the band. Typical patient symptoms include immediate dysphagia, vomiting, and inability to take oral food or liquid. Either anterior or posterior prolapse may occur. Reoperation laparoscopically to reduce the prolapse and resuture the band imbrication is indicated. (See Schwartz 9thed., p 961.)

10. Which of the following is a component of the Roux-en-Y gastric bypass?

A. Creation of a gastric pouch approximately 100 mL in volume

B. A proximal (biliopancreatic) limb >100 cm in length

C. A Roux (alimentary) limb 75-150 cm in length

D. Placing the Roux limb in a retrocolic position

Answer: C

The major feature of the operation is the creation of a proximal gastric pouch of small size (often 20 mL) that is totally separated from the stomach. A Roux limb of proximal jejunum is brought up and anastomosed to the pouch. The pathway of that limb can be anterior to the colon and stomach, posterior to both, or posterior to the colon and anterior to the stomach. The length of the biliopancreatic limb from the ligament of Treitz to the distal enteroenterostomy is from 20 to 50 cm, and the length of the Roux limb is 75 to 150 cm. (See Schwartz 9th ed., p 962.)

11. Patients undergoing Roux-en-Y gastric bypass are known to be at increased risk for developing gallstones. The current recommended management for patients with a negative ultrasound (no cholelithiasis) prior to surgery is

A. Prophylactic cholecystectomy at the time of surgery

B. Serial ultrasounds every 3 months after surgery for 2 years

C. Ultrasounds after surgery only if the patient develops symptoms

D. Oral ursodiol to prevent gallstone formation after surgery

Answer: D

We routinely perform screening ultrasound of the abdomen in patients planning to undergo LRYGB who have an intact gallbladder to rule out the presence of gallstones. Should gallstones be discovered, we currently recommend simultaneous laparoscopic cholecystectomy. Another approach is to defer cholecystectomy until after LRYGB if the patient is symptomatic. When a patient does not have gallstones as determined by preoperative ultrasound, we have followed the recommendations of a previous study which showed that prophylactic administration of ursodiol at a dosage of 300 mg bid will decrease the incidence of gallstone formation after RYGB to approximately 4%. (See Schwartz 9th ed., p 955.)

12. Which of the following is a relative contraindication to a Roux-en-Y gastric bypass?

A. Spherocytosis

B. Severe iron deficiency anemia

C. B12 deficiency

D. von Willebrand’s disease

Answer: B

Laparoscopic adjustable Roux-en-Y gastric bypass (LRYGB) is an appropriate operation to consider for most patients eligible for bariatric surgery. Relative contraindications to LRYGB include previous gastric surgery, previous antireflux surgery, severe iron deficiency anemia, distal gastric or duodenal lesions that require ongoing future surveillance, and Barrett’s esophagus with severe dysplasia.

Postoperative nutritional complications after LRYGB include iron deficiency in 20 to 40% of patients, iron deficiency anemia in 20%, vitamin B12 deficiency in 15%, and vitamin D deficiency in at least 15%, which usually is present preoperatively.

Because of the risk of postoperative iron deficiency anemia, the presence of severe iron deficiency preoperatively is a relative contraindication for surgery. (See Schwartz 9th ed., p 965.)

13. What percent of excess body weight do patients lose in the first year following Roux-en-Y gastric bypass?

A. 20-30%

B. 40-50%

C. 60-70%

D. 80-90%

Answer: C

Patients undergoing LRYGB usually lose between 60 and 80% of excess body weight during the first year after surgery. This has held true since the earliest large series of this operation was reported. Resolution of comorbidities varies depending on the disease but is >90% for GERD and venous stasis ulcers, and >80% for type 2 diabetes of 5 years’ duration. Hyperlipidemias are almost always improved and resolve totally in approximately 70% of cases. Hypertension is resolved in 50 to 65% of cases (Table 27-5). Even superobese patients who do not achieve an ultimate BMI of 35 kg/m2 can experience significant improvements in comorbidities after LRYGB or open RYGB. (See Schwartz 9th ed., pp 962, 965.)

TABLE 27-5 Effect of bariatric surgery on comorbid medical conditions

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14. A 42-year-old man who is one year status post Roux-en-Y bypass presents with a 24-hour history of intermittent vomiting. He is stable and well hydrated and his electrolytes are normal. A CT scan confirms the clinical suspicion of a partial small bowel obstruction. The appropriate initial treatment for this patient is

A. IV hydration and observation

B. IV hydration, NG tube

C. IV hydration, NG tube, and repeat CT in 24 hours

D. Immediate surgical exploration

Answer: D

Several complications that are specific to the laparoscopic adjustable Roux-en-Y gastric bypass (LRYGB) procedure must be emphasized. The most important is small-bowel obstruction. This complication must be treated differently from obstruction in the average general surgery patient, in whom it is usually caused by adhesions and often will resolve with conservative, nonoperative therapy. Patients who have undergone LRYGB who have symptoms of obstruction require surgical therapy on an emergent basis (see Table 27-6). This is because the cause of the bowel obstruction after LRYGB is often an internal hernia from inadequate closure or nonclosure of the mesenteric defects by the surgeon at the time of operation. Treatment for these patients therefore differs from that for most patients with small-bowel obstruction. The single most important point made in this chapter is to caution general surgeons to be aware of the need to operate emergently on patients who present with small-bowel obstruction after LRYGB. Currently centers that perform small-bowel transplantation are finding that the leading patient group referred for that procedure is patients who had small-bowel obstruction after LRYGB, developed infarction of most of the bowel from the internal hernia, and have short-gut syndrome. (See Schwartz 9th ed., p 966.)

TABLE 27-6 Complications for which patients undergoing laparoscopic Roux-en-Y gastric bypass require urgent surgical intervention

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15. A postoperative marginal ulcer in a patient who has undergone a Roux-en-Y gastric bypass is best treated by

A. Triple therapy for Helicobacter pylori

B. Proton pump inhibitors

C. Endoscopic dilation with post-dilation proton pump inhibitors

D. Resection of the ulcer with surgical revision of the gastrojejunostomy

Answer: B

Marginal ulcers are another complication relatively specific to Roux-en-Y gastric bypass (RYGB), either laparoscopic adjustable Roux-en-Y gastric bypass (LRYGB) or open RYGB. The patient presents with pain in the epigastric region that is not altered by eating. Diagnosis is by endoscopy. Treatment is medical with administration of proton pump inhibitors, which are effective in 90% of cases. Only those with a gastrogastric fistula to the distal stomach or severe stenosis of the lumen of the gastrojejunostomy or non-healing ulcers require surgical therapy. (See Schwartz 9th ed., p 966.)

16. Which of the following is a component of a biliopancreatic diversion?

A. Creation of a gastric pouch approximately 20 mL in volume

B. Oversewing of the distal duodenum

C. Creation of a Roux limb at least 150 cm in length

D. Prophylactic cholecystectomy

Answer: D

The operation, which is pictured in Fig. 27-1, involves resection of the distal half to two thirds of the stomach and creation of an alimentary tract of the most distal 200 cm of ileum, which is anastomosed to the stomach. The biliopancreatic limb is anastomosed to the alimentary tract either 75 or 100 cm proximal to the ileocecal valve, depending on the protein content of the patient’s diet. This operation met with limited international popularity, probably due to the technical difficulty of performing it combined with the significant percentage of nutritional complications that arise postoperatively.

The biliopancratic diversion (BPD) operation begins with performance of a distal subtotal gastrectomy. A residual 200-mL gastric pouch is created for superobese patients and a slightly larger pouch for patients with a BMI of 50 kg/m2. The terminal ileum is identified and divided 250 cm proximal to the ileocecal valve. The distal end of that divided ileum is then anastomosed to the stomach, creating a 2- to 3-cm stoma. The proximal end of the ileum is then anastomosed side to side to the terminal ileum approximately 100 cm proximal to the ileocecal valve. Some surgeons perform the anastomosis only 50 cm proximal to the valve, but in these patients the likelihood of good protein intake postoperatively should be high. Prophylactic cholecystectomy is performed due to the high incidence of gallstone formation with the malabsorption of bile salts. (See Schwartz 9th ed., pp 969, 968.)

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FIG. 27-1. Configuration of biliopancreatic diversion. (Reproduced with permission from Austrheim-Smith I, et al: Evolution of bariatric minimally invasive surgery, in Schauer PR, et al (eds):Minimally Invasive Bariatric Surgery, 1st ed. New York: Springer, 2007, p 21.)

17. Which component of the biliopancreatic diversion is different from a duodenal switch procedure?

A. The size of the remaining stomach

B. The length of the alimentary limb

C. The length of the biliopancreatic limb

D. None of the above—it is the same operation

Answer: A

The deuodenal switch (DS) procedure differs from BPD only in the proximal gut portion of the operation. Instead of a distal gastrectomy, a resection of all the stomach except for a narrow lesser curvature tube is performed. The diameter of this tube is calibrated with a dilator and, if limited to an approximately 32F (11-mm) diameter, produces the optimal amount of weight loss while still allowing adequate oral intake. The duodenum is now divided in its first portion and an approximately 2-cm length of duodenum is left intact beyond the pylorus. This end of the duodenum is then anastomosed to the distal 250 cm of ileum. (See Schwartz 9th ed., pp 969, 968, and Fig. 27-2.)

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FIG. 27-2. Configuration of the duodenal switch. (Reproduced with permission from Austrheim-Smith I, et al: Evolution of bariatric minimally invasive surgery, in Schauer PR, et al (eds): Minimally Invasive Bariatric Surgery, 1st ed. New York: Springer, 2007, p 22.)