BARIATRIC SURGERY, A REVIEW
 

Obesity is a major health problem approaching an epidemic proportions. An NIH consensus conference on the surgical treatment of obesity recommended consideration of surgery in patients with a BMI of greater than 40 kg/m2 without medical complications or a BMI of greater than 35 kg/m2 if a severe comorbidity were present. Nearly all morbidly obese patients with satisfactory postoperative weight loss, experience substantial improvement in the quality of their lives. At present, Roux en Y Gastric Bypass (RYGB) may be the only bariatric operation that has produced durable long-term weight loss at an acceptable level of risk. Complications, either peri-operative or delayed occur frequently. Early recognition of these complications and meticulous attention to details are thus of paramount importance in this group of high-risk patients.

Acknowledgement

This article is based largely on:

 Ferri's Clinical Advisor: Instant Diagnosis and Treatment, 2004 ed., Copyright © 2004 Mosby,
 Feldman: Sleisenger & Fordtran's Gastrointestinal and Liver Disease, 7th ed., Copyright © 2002 Elsevier
 www.Mdconsult.com current practice
 GASTRIC BYPASS Robert E. Brolin MD Bariatric Surgery Program, Saint Peter's University Hospital, New Brunswick, New Jersey. Surgical Clinics of North America Volume 81 • Number 5 • October 2001 Copyright © 2001 W. B. Saunders Company




INTRODUCTION

Obesity is a major health problem approaching an epidemic proportions. Consider the following:
• Approximately 97 million adults in the U.S. are overweight or obese.
• From 1960 to 1999, the prevalence of excess weight (BMI ≥25 kg/m2 ) increased from 44% to 61% of the adult population, and the prevalence of obesity (BMI ≥30 kg/m2 ) doubled, from 13% to 27%.
• The Third National Health and Nutrition Examination Survey (NHANES III) estimated that 13.7% of children and 11.5% of adolescents are overweight.
• According to NHANES III data, 54.9% of U.S. adults aged 20 yr. and older are either overweight or obese (32.6% are overweight with BMI 25to 29.9; 22.3% are obese with BMI ≥30).
• For persons with a BMI of ≥30 kg/m2 , all-cause mortality is increased by 50% to 100% above that of persons with BMIs in the range of 20 to 25 kg/m2 .
• In 1993 the Deputy Assistant Secretary for Health concluded that a combination of dietary factors and sedentary activity patterns accounts for at least 300,000 deaths each year, and obesity is the second leading cause of preventable death in the United States.
• Obesity increases the risk of developing hypertension, hyperlipidemia, type 2 diabetes, coronary artery disease, cerebrovascular disease, osteoarthritis, sleep apnea, and endometrial, breast, prostate, and colon cancers.
• Obesity accelerates the progression of coronary atherosclerosis in young men (age range 15 to 34 yr).
• All-cause mortality is increased in obese patients.
• The total cost attributable to obesity in 1995 was $99.2 billion dollars or 5.7% of the national health expenditure within the U.S.
Severe obesity is a chronic condition that is difficult to treat through diet and exercise alone. Gastrointestinal surgery for obesity, also called bariatric surgery, is an option for persons who are severely obese and cannot lose weight by traditional means or who suffer from serious obesity-related health problems. Studies show that most persons lose weight quickly after surgery and continue to lose weight for 18 to 24 months after the procedure. Although most persons regain 5% to 10% of the weight they lost, many maintain a long-term weight loss of about 100 pounds. In addition, surgery improves most obesity-related conditions.
Bariatric is derived from the Greek term baros, meaning weight. Bariatric surgery creates an anatomic barrier preventing over-consumption and accumulation of excess calories either by restricting the gastric reservoir or by inducing malabsorption. Since these two approaches are complementary, they are frequently combined in a single operative procedure.

INDICATIONS

Bariatric surgery should be considered in persons with a body mass index (BMI) above 40—about 100 pounds of excess weight for men and 80 pounds for women. Persons with a BMI between 35 and 40 who suffer from type 2 diabetes or life-threatening cardiopulmonary problems such as severe sleep apnea or obesity-related heart disease may also be candidates for surgery. In addition, a person with obesity-related physical problems that interfere with employment, walking, or family function may be a candidate.
Body mass index is determined by dividing a person's weight in kilograms by height in meters squared. To determine BMI using pounds and inches, multiply the patient's weight in pounds by 704.5, then divide the result by the patient's height in inches, and divide that result by the patient's height in inches a second time.
An NIH consensus conference on the surgical treatment of obesity recommended consideration of surgery in patients with a BMI of greater than 40 kg/m2 without medical complications or a BMI of greater than 35 kg/m2 if a severe comorbidity were present. Other factors to consider are:

 BMI > 35 kg/m2 and significant obesity comorbidity (e.g., hypertension, diabetes, sleep apnea, pickwickian syndrome, incapacitating osteoarthritis)
 Documented failure to keep weight off or to prevent further weight gain using aggressive medical management that has included behavioral, pharmacologic, and low-calorie-diet components
 Psychological ability to comprehend the expected changes in dietary intake necessary following surgery to achieve and sustain weight loss
 Willingness to maintain continued medical management following surgery, including visits to registered dietitians, internists
 Adult, nonpregnant, absence of drug addiction or chronic disease unrelated to obesity

BARIATRIC SURGERY

Bariatric surgery alters the digestive process and is classified into two categories: restrictive and malabsorptive.

Restrictive procedures

Restrictive procedures promote weight loss by closing off parts of the stomach to make it smaller, thus restricting the amount of food the stomach can hold. Restrictive procedures do not interfere with the normal digestive process.
To perform the surgery, a small pouch is created at the top of the stomach where food enters from the esophagus. Initially, the pouch holds about 1 ounce of food and later expands to 2 to 3 ounces. The lower outlet of the pouch usually has a diameter of only about ¾ inch. This small outlet delays the emptying of food from the pouch and causes a feeling of fullness. As a result of this surgery, most persons lose the ability to eat large amounts of food at one time. After an operation, the person usually can eat only ¾ to 1 cup of food without discomfort or nausea. Also, food has to be well chewed.

Restrictive operations for obesity include the following:
Adjustable gastric banding: In this procedure, a hollow band made of special material is placed around the stomach near its upper end, creating a small pouch and a narrow passage into the larger remainder of the stomach. The band is then inflated with a salt solution. It can be tightened or loosened over time to change the size of the passage by increasing or decreasing the amount of salt solution.
Vertical banded gastroplasty: This procedure has been the most common restrictive operation for weight control. In this procedure, both a band and staples are used to create a small stomach pouch.

Malabsorptive procedures,

The most common gastrointestinal surgeries for weight loss, combine stomach restriction with a partial bypass of the small intestine. A direct connection from the stomach to the lower segment of the small intestine is created, bypassing portions of the digestive tract that absorb calories and nutrients.
Malabsorptive operations for obesity include the following:
Roux-en-Y gastric bypass: This operation is the most common and successful malabsorptive surgery. First, a small stomach pouch is created to restrict food intake. Next, a Y-shaped section of the small intestine is attached to the pouch to allow food to bypass the lower stomach, the duodenum, and the first portion of the jejunum. This bypass reduces the amount of calories and nutrients the body absorbs.
Biliopancreatic diversion (BPD): In this more complicated malabsorptive operation, portions of the stomach are removed. The small pouch that remains is connected directly to the final segment of the small intestine, completely bypassing the duodenum and the jejunum. Although this procedure successfully promotes weight loss, it is used less frequently than other types of surgery because of the high risk for nutritional deficiencies. A variation of BPD includes a "duodenal switch," which leaves a larger portion of the stomach intact, including the pyloric valve that regulates the release of stomach contents into the small intestine. It also keeps a small part of the duodenum in the digestive pathway.
Malabsorptive operations produce more weight loss than do restrictive operations and are more effective in reversing the health problems associated with severe obesity. Persons who have malabsorptive operations generally lose two thirds of their excess weight within 2 years.

Although restrictive operations lead to weight loss in almost all persons, they are less successful than malabsorptive operations in achieving substantial, long-term weight loss. About 30% of those who undergo vertical banded gastroplasty achieve normal weight, and about 80% achieve some degree of weight loss. Some persons regain weight. Others are unable to adjust their eating habits and fail to lose the desired weight. Successful results depend on the patient's willingness to adopt a long-term plan of healthy eating and regular physical activity.

PREOPERATIVE PREPARATION

Preparation of patients for bariatric operations varies according to the underlying health of individual patients. Most patients can be admitted to the hospital on the day of operation; however, patients with severe sleep apnea syndrome or congestive heart failure may require hospitalization for two or three days before operation to optimize their cardiopulmonary risk status. All patients should be given intravenous prophylactic antibiotics perioperatively.

Because the incidence of cholelithiasis is 15% to 25% in morbidly obese patients, pre- or intraoperative screening for gallstones is recommended in all patients who have not had cholecystectomy. Cholecystectomy should be performed in all patients with cholelithiasis at the time of gastric bypass.
An active peptic ulcer represents an absolute contraindication for bariatric surgery. Approximately 15% of our preoperative patients have tested positive for H pylori infestation; this finding is similar to that of other surgeons. H pylori is easily managed by administering a two-week course of antibiotics and H2 receptor blockers.

OPERATIVE CONSIDERATIONS

Severely obese patients tolerate general anesthesia remarkably well. However, endotracheal intubation may be difficult, particularly in patients who weigh more than 400 lbs. Approximately 20% of patients require admission to the intensive care unit postoperatively. However, all patients with sleep apnea, congestive heart failure, and severe asthmatic bronchitis should spend one or two nights in the intensive care unit for close monitoring of their cardiopulmonary status. Many of these patients require overnight intubation.
Because obesity is considered a risk factor for postoperative pulmonary embolism, a variety of prophylaxis methods have been employed to prevent this feared complication. These include subcutaneous low-dose anticoagulants, pneumatic compression stockings, elastic stockings or bandages, intravenous low-molecular-weight dextran, and using the Trendelenburg position intraoperatively. Early postoperative ambulation is strongly encouraged and almost certainly contributes to the low incidence of postoperative venous thromboembolism (1%-2%) that has been reported in these patients. Patients are assisted in getting out of bed on the night of the operation and are walked on the first postoperative day.

Ice chips and sips of water are given by mouth a few hours after the nasogastric tube is removed from the patient. If the patient tolerates the water and ice, a clear liquid diet is begun the following day. Intravenous fluids are usually discontinued after the patient tolerates clear liquids without difficulty. A maximum 1,000-calorie full liquid diet is given on the next day and is continued until discharge. Patients are usually discharged on the third or fourth postoperative day. A limited UGI contrast study is routinely performed shortly before the patient is discharged to examine the integrity of the staple line and outlet stoma.
Patients are instructed to follow a pureed diet for four weeks after discharge. The purpose of this modified liquid diet is twofold: first, it allows time for patients to adjust to their tremendously restricted stomach capacity by consuming foods that are relatively easy to chew and swallow. Second, it minimizes the likelihood of vomiting in the early postoperative period. Repeated episodes of vomiting in the early postoperative period have been associated with staple-line disruption and leaks. After four weeks, patients begin a soft solid diet with instructions to introduce new foods gradually, until they achieve a normal diet. All patients should take a daily multivitamin supplement with minerals for the rest of their lives. After distal RYGB, some patients may require additional protein and other nutritional supplements. Gastric bypass patients require periodic blood tests to monitor possible metabolic and nutritional deficiencies.
Weight loss after gastric bypass generally peaks somewhere between 65% and 80% of excess weight loss between 12 and 18 months postoperatively. However, some degree of recidivism occurs between three and five years after RYGB. Five-year weight loss results in large clinical series of gastric bypass patients show a mean excess weight loss ranging from 50% to 60%. Weight-loss results reported after RYGB have been superior to those observed after other gastric restrictive operations.

COMPLICATIONS FROM BARIATRIC SURGERY

General complications

Weight loss from dieting or bariatric surgery further increases the risk of gallstones. The incidence of new gallstones has been estimated at 12% during very-low-calorie dieting and 38% after successful gastric bypass surgery. Higher initial BMI and greater absolute rate of weight loss are significant and independent predictors.

Large and rapid weight loss has been shown to increase the prevalence of inflammatory hepatitis. One case report describes the development of occult cirrhosis in a patient whose preoperative liver biopsy was normal. Two series of patients who had liver biopsies pre- and postweight reduction have been reported. The increase in the prevalence of hepatitis is not due to surgical therapy but rather to the weight loss itself.

Specific Complications

The more extensive the bypass, the greater the risk for complications and nutritional deficiencies. Persons with extensive bypasses of the normal digestive process require close monitoring and life-long use of special foods, supplements, and medications.

A common risk of restrictive operations is vomiting, which is caused when the small stomach is overly stretched by food particles that have not been chewed well. Band slippage and saline leakage have been reported after adjustable gastric banding. Risks of vertical banded gastroplasty include wearing away of the band and breakdown of the staple line. In a small number of cases, stomach juices may leak into the abdomen, requiring an emergency operation. In fewer than 1% of all cases, infection or death from complications may occur.

In addition to the risks of restrictive surgeries, malabsorptive operations also carry greater risk for nutritional deficiencies. This is because the procedure causes food to bypass the duodenum and jejunum, where most iron and calcium are absorbed. Nearly 30% of persons who undergo weight-loss surgery develop nutritional deficiencies such as anemia, osteoporosis, and metabolic bone disease. These deficiencies usually can be avoided if vitamin and mineral intakes are high enough.

Ten to 20 percent of persons who have weight-loss surgery require follow-up operations to correct complications. Abdominal hernia had been the most common complication requiring follow-up surgery, but laparoscopic techniques seem to have reduced this problem. Persons who are superobese (>350 pounds) or have had previous abdominal surgery may not be good candidates for laparoscopy. Less common complications include breakdown of the staple line and stretched stomach outlets.

Roux-en-Y gastric bypass and BPD operations may also cause "dumping syndrome." This means that stomach contents move too rapidly through the small intestine. Symptoms include nausea, weakness, sweating, faintness, and sometimes diarrhea after eating. Because the duodenal switch operation keeps the pyloric valve intact, it may reduce the likelihood of dumping syndrome.


INTRAOPERATIVE COMPLICATIONS

Complications that occur during bariatric operations can be divided into three categories: (1) bleeding (including splenic injury), (2) inadvertent injury to the GI tract, and (3) stapling misadventures. The incidence of intraoperative complications in the best series 1.4%. . Although intraoperative complications generally can be avoided by unabated concentration and careful technique, the injuries can be successfully corrected or repaired if recognized intraoperatively. Intraoperative complications should be rare in experienced hands.

EARLY POSTOPERATIVE COMPLICATIONS

Pulmonary embolism is the leading cause of perioperative death in bariatric surgical patients. The incidence of pulmonary embolism is reported in the range of 1% to 2% in most large series of bariatric operations. Nearly one-third the number of bariatric patients who suffer pulmonary embolism die. Unfortunately, the incidence of pulmonary embolism does not seem to be altered by routine use of methods of perioperative DVT prophylaxis. of anticoagulant therapy.

The incidence of gastrointestinal leaks after primary gastric bypass operations is reported in the range of 1% to 2%. Leaks are sometimes difficult to recognize after gastric bypass because fever and abdominal tenderness are frequently absent. The leukocyte count is often elevated but may be within normal limits. Left shoulder pain and anxiety are early symptoms. Persistent tachycardia and progressive tachypnea are the most common early signs. Hence, it is common to initially suspect pulmonary embolism in a patient with a gastric leak.

Most surgeons attempt to identify leaks using radiographic GI contrast studies. However, a normal contrast study by no means excludes a leak, since extravasation from the gastric staple line is usually not identified by GI contrast studies. An isolated left-sided pleural effusion is a common finding on the plain chest radiograph. Because failure to recognize a leak can result in the patient's death, exploratory laparotomy should be empirically performed in patients with progressive tachypnea and tachycardia in whom pulmonary embolism has been ruled out. In patients who are rapidly deteriorating, exploratory surgery should be undertaken without GI radiographs. The incidence of leaks following revision procedures is 5 to 10 times higher than after primary operations, presumably because of problems with ischemic damage to the stomach.

The incidence of major wound infection after gastric bypass is reported in the range of 1% to 3%. Conversely, seromas in the subcutaneous fatty layer are common, with an incidence approaching 40%. The potential for wound dehiscence after gastric bypass is greatly increased because of the tension placed on the closure by massive overweight. Hence, the abdominal fascia should be closed with heavy absorbable or nonabsorbable suture. The incidence of fascial dehiscence is in the range of 1.0% in large published series.
Gastrointestinal bleeding within the 30-day perioperative interval may have a variety of causes, including marginal ulceration, ulcers in the bypassed stomach or duodenum, gastritis, and bleeding from fresh staple lines.
Small bowel obstruction (SBO) within the first several weeks postoperatively may occur in 1% to 2% of patients. Most cases of early obstruction can be treated successfully by tube decompression, which is best accomplished using fluoroscopy.
Cardiorespiratory complications are surprisingly uncommon after gastric bypass. Sudden cardiac arrest is quite rare in the postoperative period, and death after cardiac arrest is often the result of inability to intubate patients who develop acute respiratory distress. Intubation under these difficult circumstances should be deferred to experienced health professionals skilled in awake intubation.

LATE COMPLICATIONS

Incisional hernia is the most common late complication after open gastric bypass, with an incidence ranging from 10% to 20% in most large series.
The reported incidence of symptomatic gallbladder disease after bariatric operations ranges from 3% to 30%. The practice of removing the gallbladder prophylactically at the time of surgery has been a controversial issue among bariatric surgeons. Several surgeons who have recommended prophylactic cholecystectomy report histologic evidence of gallbladder pathology in 90% of cases.
Although vomiting is a common side effect of gastric bypass in the early postoperative period, severe intractable vomiting is rare. Most cases of severe vomiting are caused by stenosis of the outlet stoma. Patients with vomiting who cannot tolerate liquids should be hospitalized and placed on intravenous fluids. In many cases the edema of the outlet stoma, which results from protracted vomiting, will resolve without further intervention. Patients who cannot tolerate liquids after several days of nothing by mouth and intravenous fluids should undergo upper endoscopy and stomal dilatation using balloon-tipped catheters. Stomal dilatation is usually successful, except in patients with prosthetic stomal reinforcement. Many patients with prosthetic stomal reinforcement require reoperation for intractable stomal stenosis.

Late disruption (breakdown) of the stapled gastric partition is responsible for patients regaining lost weight after gastric bypass. However, the incidence of staple-line breakdown varies widely in clinical reports from 2% to 23%. This finding led to a prospective trial of stapling versus transsection of the upper stomach. The East Carolina group abandoned transsection after 100 cases when they observed that dividing the stomach neither eliminated subsequent gastro-gastric fistulae nor reduced the incidence of leaks. Despite conflicting data, most surgeons now routinely divide the stomach during gastric bypass. The incidence of staple-line leaks and gastro-gastric fistulae after transsection are reported in the range of 1% to 2%.

The reported incidence of marginal ulcer after RYGB ranges from 3% to 10%. These ulcers typically develop on the jejunal side of the gastroenterostomy and are caused by excessive production of gastric acid. Many cases of marginal ulcers are associated with breakdown of the gastric staple line. Marginal ulcers that are not associated with disruption of the stapled partition almost always respond to H2 blockers or proton pump inhibitors. Conversely, ulcers that occur in patients with staple-line breakdown are often intractable to medications and require operative treatment.

Although intestinal obstruction is relatively uncommon after gastric bypass, it may be life threatening. The incidence of SBO after RYGB and other malabsorptive procedures is in the range of 2% to 3%. Because gastric capacity is greatly reduced after RYGB, vomiting is often not a prominent symptom. Although most cases of late SBO are caused by adhesions, volvulus related to internal hernia is a recognized, occasionally fatal type of obstruction. Because obstruction of the bypassed bowel may not be obvious on plain abdominal radiographs, CT scanning should be promptly performed when abdominal films are nondiagnostic. Aggressive operative treatment is warranted in patients whose symptoms are not quickly improved with tube decompression.

METABOLIC SEQUELAE

Patients who have gastric bypass are at risk of developing several metabolic sequelae. . Since iron absorption occurs primarily in the duodenum, malabsorption of ingested iron is the primary cause of post-gastric bypass iron deficiency. Vitamin B12 deficiency after gastric bypass is the result of failure to cleave food-bound B12 from its protein moiety in the upper gastric pouch. Conversely, crystalline B12 is absorbed normally in the distal ileum. Although the etiology of folate deficiency after gastric bypass is unknown, inadequate dietary intake is probably the most common cause. Deficiencies in each of these micronutrients can result in anemia. Because these deficiencies are common, daily prophylactic multivitamin/mineral supplements are recommended for all patients who have gastric bypass.
Because fat malabsorption is a goal of the distal "malabsorptive" gastric bypass, patients who have these procedures are prone to develop diarrhea, malodorous flatus, and deficiencies in fat-soluble vitamins. Calcium deficiency and hypoproteinemia may also occur after distal RYGB. Fortunately, the majority of post-gastric bypass vitamin and mineral deficiencies are mild and are easily corrected by taking oral supplements of the deficient micronutrient.

REVISION OPERATIONS

Patients who have gastric bypass occasionally require revision, either for inadequate weight loss or for complications. The incidence of major postoperative complications following revisional bariatric procedures is substantially higher compared to primary operations. Early morbidity rates range from 15% to 50%. The mortality rate reported after revision operations ranges as high as 10%, Undoing any bariatric operation without conversion to another weight-reduction procedure is invariably associated with the patient's promptly regaining the lost weight. The most common complication resulting in reoperation is intractable marginal ulcer.
Gastric bypass patients with anatomically intact operations and unsatisfactory weight loss have probably "outeaten" the operation. Gastric bypass patients with unsatisfactory weight loss are best converted to a more malabsorptive modification of RYGB, or in some cases biliopancreatic diversion. Unfortunately, some patients who are converted to a malabsorptive procedure suffer severe metabolic complications. Patients with staple-line breakdown after RYGB should have transection of the stomach between staple lines because of the high incidence of subsequent disruption observed in patients who have had restapling in continuity. RYGB patients with stomal stenosis and an intact staple line who fail endoscopic dilatation should have revision of the gastroenterostomy. Large-volume gastric pouches should be reduced when technically feasible.

A small number of morbidly obese patients will outeat any bariatric operation. Whenever a patient has failed a second technically sound and intact operation, surgeons should approach the prospect of a further revision with considerable caution and skepticism. Rejection of such patients for another operation is frequently a prudent decision.

 

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