Management of Obesity


Figure 46-1. Jejunoileal bypass. The jejunum is divided 14 in distal to the ligament of Treitz, and a jejunoileostomy is created 4 in proximal to the ileocecal valve. Note that the defunctionalized jejunoileal limb is out of continuity with biliopancreatic effluent, predisposing to limb stasis.



Gastric Bypass – The Gold Standard


With the decline of jejunoileal bypass, surgeons began searching for alternatives. In the 1960s, Edward Mason at the University of Iowa experimented with operations based on observations that patients who underwent gastric resections for ulcer disease had difficulty maintaining their weight. Mason’s efforts led to the development of the gastric bypass, for which he earned the title “father of bariatric surgery.” Mason’s original gastric bypass consisted of a pouch gastroplasty with a loop gastrojejunostomy reconstruction. Gastric bypass subsequently evolved through a number of iterations, all with important clinical implications. Large horizontal fundal-based pouches were replaced with smaller vertical lesser curve-based pouches, which improve gastric emptying. Undivided gastric pouches were associated with high rates of staple-line dehiscence and gastrogastric fistula, and were replaced with divided gastric bypass, expedited by the development of cutting staplers. Roux-en-Y reconstruction, compared to loop reconstruction, reduces tension on the gastrojejunal anastomosis and prevents bile reflux gastritis, but may be associated with higher rates of anastomotic ulcer disease. Retrocolic Roux limbs may improve pouch emptying and generate less tension on the gastrojejunostomy, but at the price of higher rates of mesocolic internal hernias. Banding of the gastrojejunal anastomosis may increase weight loss, but also increases risks of stenosis, obstruction, and erosion. Variations persist, including retrocolic Roux limbs, loop reconstructions (“minigastric bypass”), and prosthetic-banded gastric pouches. The modern gastric bypass practiced by the majority of surgeons today consists of a divided, unbanded, lesser curve-based pouch gastroplasty of 15 to 30 cc with an antecolic Roux-en-Y gastrojejunal reconstruction with a 100-cm Roux/alimentary limb and a 50- to 100-cm afferent/biliopancreatic limb (Fig. 46-2). The modern gastric bypass is a robust operation because within limits, subtle variations in technique, including pouch size and morphology and intestinal limb length and position, do not greatly affect efficacy or morbidity. Gastric bypass remains, as of this writing, the dominant bariatric operation worldwide and the gold standard against which all other operations are measured.




Figure 46-2. Anatomy of modern Roux-en-Y gastric bypass. Modern gastric bypass consists of a divided pouch gastroplasty with Roux-en-Y jejunojejunal reconstruction. The Roux limb is most commonly placed in the antecolic position. Intestinal limbs are termed with either standard Roux (Roux, afferent, efferent) or bariatric (alimentary, biliopancreatic, common channel) nomenclature as shown.


Malabsorption Revisited


Despite the failure of jejunoileal bypass, interest in operations that relied on small intestine bypass persisted. Biliopancreatic diversion consists of an antrectomy with a gastrojejunostomy and distal Roux-en-Y jejunoileostomy. The duodenal switch modification of the biliopancreatic diversion involves a sleeve gastrectomy, division of the duodenum distal to the pylorus, and a duodenojejunostomy and distal Roux-en-Y jejunoileostomy, thus maintaining the pylorus in the alimentary stream (Fig. 46-3). Biliopancreatic diversion/duodenal switch differs from jejunoileal bypass in two important regards. First, maintenance of forward flow of biliopancreatic effluent in the bypassed afferent limb prevents stasis and bacterial overgrowth. Second, common channel length was increased to 100 cm, reducing malabsorptive complications. Biliopancreatic diversion/duodenal switch provides weight loss and metabolic disease remission equivalent to, and in many series, greater than gastric bypass. Morbidity and mortality for biliopancreatic diversion/duodenal switch span a wide range, with centers with significant expertise reporting low rates similar to gastric bypass. Nonetheless, when the literature as a whole is considered, biliopancreatic diversion/duodenal switch is associated with higher morbidity and mortality than gastric bypass. Perioperative mortality reported by meta-analyses is at least twofold higher than gastric bypass, possibly due to a higher risk of anastomotic dehiscence, as laparoscopic creation of the duodenojejunal anastomosis associated with the duodenal switch modification is technically challenging.22 Late malabsorptive complications which may require surgical revision, while much improved over jejunoileal bypass, range from 2% to 20%. Unlike gastric bypass, in which small changes in pouch size or limb length do not substantially alter clinical outcome, outcomes of biliopancreatic diversion/duodenal switch are relatively sensitive to differences in efferent limb length, small changes in which may make the difference between poor weight loss and malabsorptive complications. Predicting the correct efferent limb length for an individual patient is challenging. Most surgeons advocate a fixed length of 100 cm, while others advocate an ad hoc limb length proportional to total small intestine length. While advocated by select surgeons and associated with good outcomes in centers with significant experience, biliopancreatic diversion/duodenal switch is nonetheless waning in use, currently comprising less than 2% of bariatric operations.




Figure 46-3. Biliopancreatic diversion (BPD). BPD involves a distal antrectomy with a Roux-en-Y jejunoileal reconstruction; BPD+DS involves a sleeve gastrectomy with a Roux-en-Y duodenolieal reconstruction, with the duodenoileostomy created 2 cm distal to the pylorus, thus preserving the pyloric emptying mechanism. Note that, unlike JIBP, the afferent/biliopancreatic jejunoileal limb is in continuity with biliopancreatic effluent, reducing limb stasis.


Pure Restriction


In Mason’s era, morbidity from gastric bypass was not trivial. In an effort to design a simpler and safer operation, Mason experimented with gastroplasties that precluded the need for small intestinal reconstruction. Like gastric bypass, these operations evolved through a number of iterations, eventually leading to the modern vertical banded gastroplasty, which involves creation of a partitioned upper stomach pouch with a prosthetic band restricting pouch outlet diameter (Fig. 46-4). Vertical banded gastroplasty achieved widespread acceptance and peaked in the 1970–80s. Vertical banded gastroplasty weight loss is substantially less and late weight regain substantially greater compared to gastric bypass, however, and vertical banded gastroplasty has therefore been relegated to a minority operation that is rapidly being eliminated from use.


Study of prosthetic bands applied to the upper stomach to limit food intake began in the late 1970s using devices made from prolene, marlex, and other materials. These devices were nonadjustable and plagued with complications related to erosion, migration, stenosis, and obstruction. Efforts persisted, eventually culminating in the modern adjustable gastric band, a silicone device that was FDA approved in the United States in 2001 (Fig. 46-5). A primary advantage of gastric band is its technical simplicity and low rates of major morbidity and mortality. Unlike gastric bypass, which continues to be associated with low but finite rates of anastomotic dehiscence and mortality, gastric band is associated with 5 to 10 lower rates of life-threatening complications and mortality. Much enthusiasm accompanied the introduction of gastric band in the late 1990s, but over the past decade, enthusiasm has waned for two reasons. First, therapeutic efficacy of gastric band in the majority of patients is substantially less than gastric bypass. Second, as years passed, late complication rates have increased. These complications, including band slippage, erosion, and esophageal dilation and development of gastroesophageal reflux disease (GERD), are usually not life-threatening, but range between 10% and 50% and often lead to band removal.23 Despite these problems, gastric band efficacy, while not as high as gastric bypass, is acceptable. Gastric band remains the bariatric operation with the lowest major morbidity and mortality rates, an appealing quality for risk-averse patients. Gastric band does not require Roux-en-Y reconstruction, an advantage in patients with complex abdominal surgical histories. For these reasons, gastric band remains an important component of the bariatric surgery repertoire.




Figure 46-4. Vertical banded gastroplasty. A partitioned proximal gastric pouch is created with a linear stapler, and outflow limited with a prosthetic band. Variations included a divided staple line and different materials used for banding.




Figure 46-5. Gastric band. A silicone adjustable band is positioned around the upper stomach, creating a gastric pouch. A port attached to the band via silicone tubing is placed in the subcutaneous tissue in the abdominal wall, permitting percutaneous access and adjustment of band diameter.


Sleeve gastrectomy was introduced initially as a component of the duodenal switch modification of biliopancreatic diversion, but did not gain significant attention as a stand-alone bariatric operation until the early 2000s. Sleeve gastrectomy involves a lateral gastrectomy, leaving a narrow “sleeve” of stomach 32 to 40 Fr in diameter (Fig. 46-6). Originally proposed as the first step in a staged approach for high BMI patients prior to definitive gastric bypass, early follow-up data demonstrated excellent results, and long-term efficacy appears similar to gastric bypass. Sleeve gastrectomy is associated with perioperative complication rates similar to gastric bypass, but late complications are rare, in part due to elimination of morbidity associated with alterations in small intestinal anatomy. For these reasons, sleeve gastrectomy has engendered significant enthusiasm and is rapidly increasing in utilization.




Figure 46-6. Sleeve gastrectomy. A lateral gastrectomy is performed with a linear cutting stapler, creating narrow gastric reservoir 32 to 40 Fr in diameter.


Modern Bariatric Surgery


6 Bariatric operations in addition to those described above exist, including variants of gastric bypass, biliopancreatic diversion/duodenal switch, and vertical banded gastroplasty as well as distinct alternative operations. Currently gastric bypass, sleeve gastrectomy, and gastric band are the mainstays, while biliopancreatic diversion/duodenal switch comprises a waning minority. Worldwide utilization rates in 2011 were gastric bypass 47%, sleeve gastrectomy 28%, gastric band 18%, and biliopancreatic diversion/duodenal switch 2% of all bariatric operations, with a marked increase in sleeve gastrectomy and decrease in gastric band in recent years.24 The introduction of laparoscopy in the early 1990s provided significant advantages for many surgical patients but perhaps none more so than the obese. Wound infections and ventral hernias afflicted 30% to 90% of patients undergoing bariatric surgery via laparotomy, complications that were virtually eliminated with laparoscopy. Surgeons began exploring laparoscopic gastric bypass in the mid-1990s, but laparoscopy came with a price, introducing technical challenges dissimilar from open bariatric surgery, with a long, arduous learning curve that may exceed 100 cases for laparoscopic gastric bypass. These challenges engendered a response that included fellowship training programs and programmatic efforts to codify technique and care, including certification of bariatric surgery centers by surgical societies. These efforts, along with increasing surgeon experience, have reduced current morbidity and mortality to levels substantially lower than in the prelaparoscopic era. Currently, a laparoscopic approach is considered standard of care for bariatric surgery patients in the absence of a prohibitive prior surgical history.


Efficacy


Bariatric surgery achieves dramatic results. Weight loss is commonly reported as a percent age of excess weight lost (EWL), defined as the difference between presurgical weight and ideal weight, with ideal weight calculated for BMI = 25 for height. Weight loss typically peaks 1 to 2 years after surgery and may approach 80% to 90% EWL, followed by partial weight regain 3 to 10 years after surgery, leading to a plateau at 50% to 70% EWL at long-term follow-up.25 The mechanisms underlying this weight loss pattern are unknown but may involve development of adaptive eating patterns that increase caloric intake over time. For gastric band, weight loss is typically slower and more gradual, with a plateau after 2 to 3 years. These varying patterns of weight loss complicate comparison of results of different operations and analysis of published data due to variable length of follow-up among studies. Analysis is further complicated by significant attrition of patients over long-term follow-up in most studies. Despite these challenges, meta-analyses, controlled trials, and uncontrolled case series provide estimates of the efficacy of bariatric operations (Table 46-1). Weight loss is highest for biliopancreatic diversion/duodenal switch, ranging from 55% to 75% EWL, followed by gastric bypass and sleeve gastrectomy (50% to 70% EWL) and gastric band (40% to 60% EWL).



Table 46-1 Bariatric Surgery Long-Term Weight Loss Responses



Rates of improvement and remission of metabolic diseases parallel weight loss, with gastric bypass, sleeve gastrectomy, and biliopancreatic diversion/duodenal switch associated with higher remission rates than gastric band. Diabetes, steatosis, sleep apnea, hypertension, and hyperlipidemia improvement/remission rates range from 60% to over 90% (Table 46-2). Weight loss is durable, lasting decades in most patients, and accompanied by marked reductions in long-term incident diabetes, cardiovascular disease, and cancer, increased quality of life, reduced long-term healthcare costs, and a 25% to 40% reduction in long-term mortality. Randomized controlled trials demonstrate that bariatric surgery is substantially more efficacious than medical therapy for weight loss and diabetes, and multiple medical societies, including the American Diabetes Association, the International Diabetes Federation, and the American Heart Association, endorse bariatric surgery as treatment for metabolic disease.


Despite its efficacy, results of bariatric surgery are variable, with a substantial minority of patients achieving significantly better than average weight loss and disease response rates, while a similar minority experience suboptimal results. Anywhere from 10% to 30% of patients achieve <50% EWL, which may be due to failure to lose weight initially, or weight regain after a period of adequate weight loss. Mechanisms underlying such failures are poorly defined, and identification of accurate predictors of response to surgery is an important area of research. While suboptimal results are often attributed to lack of patient compliance with postoperative diet and exercise, these arguments ring false, echoing similar arguments that attribute obesity itself to a lack of “willpower.” Instead, compelling evidence implicates genetic and epigenetic mechanisms. Like obesity itself, responses to bariatric surgery are highly hereditable. Ethnicity is a predictor of outcome, with Caucasians and Hispanics experiencing greater weight loss than Blacks and Asians. Multiple single-nucleotide polymorphisms have been linked to surgical outcome. Future research will identify clinical and genetic predictors of response and permit optimization of allocation of surgical resources.


Perioperative Mortality and Morbidity


Morbidity and mortality associated with bariatric surgery have decreased over the past two decades as surgeon experience increased and techniques evolved. Currently, gastric bypass and gastric band are associated with mortality risks similar to hip replacement and laparoscopic cholecystectomy, respectively. Perioperative mortality is highest for biliopancreatic diversion/duodenal switch, followed by gastric bypass and sleeve gastrectomy, then gastric band (Table 46-3). Life-threatening perioperative morbidity associated with gastric bypass and sleeve gastrectomy consists primarily of anastomotic dehiscence, staple-line leaks, hemorrhage, thromboembolic events, and cardiac events. Life-threatening perioperative morbidity associated with gastric band is rare and consists primarily of gastric perforation, thromboembolic events, and cardiac events.


The most dire perioperative complication of gastric bypass is anastomotic dehiscence of the gastrojejunostomy which usually occurs within 2 weeks of surgery. Incidences in most series range from 0.1% to 4%, although recent data suggest that anastomotic dehiscence rates are decreasing and high-volume centers report rates in the range of 0.1% to 0.2%. Signs and symptoms are similar to those of anastomotic dehiscence after any intestinal operation, but may be less apparent in the obese. Persistent tachycardia and abdominal pain are important but nonspecific sentinel signs. Upper GI radiographs may be of diagnostic utility but lack sensitivity. Abdominal CT scan, even within a few days of surgery, may be useful, as the lack of a fluid collection near the gastrojejunostomy has a high negative predictive value for leak, while contrast extravasation has a high positive predictive value. Nonetheless, data are conflicting regarding the sensitivity and specificity of radiologic studies for diagnosing anastomotic dehiscence, and laparoscopic reexploration should be employed aggressively in suspected cases. Operative management consists of washout, wide drainage, judicious attempt at repair, and distal enteral access, usually with a gastrostomy tube in the remnant stomach, although a jejunostomy tube in the distal Roux limb or biliary limb is an option if access to the remnant stomach is difficult. Anastomotic dehiscence can be managed laparoscopically in some cases, reducing the high risk of ventral hernia associated with laparotomy. Most will heal if sepsis is controlled.


Staple-line leaks are an equally dire event after sleeve gastrectomy, occurring anywhere from 1–2 weeks to many months after surgery. Leaks may occur at any point along the staple line, but when involving the thicker tissue of the antrum may be less prone to heal, and interval conversion to gastric bypass with resection of the involved portion of gastric sleeve may be necessary. Proper stapler selection and use during primary operation with avoidance of overly narrow sleeves (current consensus recommends 32- to 40-Fr diameter) reduce the risk of sleeve gastrectomy staple-line leaks, which currently occur with an incidence of approximately 1% to 3%. Gastric band is only rarely associated with perioperative septic complications, most often in the form of gastric perforation, which occurs in 0% to 0.5% of cases. Perforation, if not recognized, may be life-threatening and is a primary cause of rare perioperative mortality and major morbidity after gastric band.



Table 46-2 Bariatric Surgery Long-Term Comorbidity Responses


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May 5, 2017 | Posted by in GENERAL SURGERY | Comments Off on Management of Obesity
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