Type 2 diabetes and surgery: band or bypass?

LAGB and LRYGB are very different in their invasiveness, mechanism of weight loss and risk profiles.

Obesity is becoming the most prevalent chronic disease in the United States today. Nearly two-thirds of the population is overweight (approximately 133.6 million adults) with almost half of them classified as obese (BMI ≥ 30).

The prevalence of class III obesity (BMI ≥ 40), the category for which NIH guidelines indicate surgical therapy, increased from 0.78% in 1990 to 2.2% in 2000. Since then this number has most certainly increased, along with its attendant increase in comorbidities. Type 2 diabetes is foremost amongst these associated conditions and is responsible for significant health, social and economic impacts on our society.

Are we any closer to finding the magic bullet with which to approach this disease in our population — a surgical cure?

The two most commonly performed bariatric procedures in the United States to treat morbid obesity and its comorbidities are laparoscopic roux-en-y gastric bypass (LRYGB) and laparoscopic adjustable gastric banding (LAGB). The two procedures work in different ways and carry their own distinct risk profiles.

LAGB placement is a purely restrictive weight loss procedure that involves placement of an adjustable, silicone band around the proximal stomach, creating a small pouch that limits ingestion of food. The band is adjustable, can be removed, and its placement does not involve dividing the GI tract or creating an anastomosis. Complications associated with LAGB placement include acute dysphagia, band erosion or slippage, device or port malfunction, and infection associated with foreign body implantation. Its placement carries a mortality rate of 0% to 0.7% and is associated with 30% to 60% loss of excess weight.

Saurabh Khandelwal

Brant Oelschlager

LRYGB is both a restrictive and malabsorptive procedure. Gastric bypass involves stapling and dividing the proximal stomach to create a small gastric pouch to which a desired length of small bowel is anastomosed. The biliary-pancreatic limb is anastomosed downstream. The length of small bowel bypassed before the downstream anastomosis affects nutrient absorption and the amount of weight lost. Complications associated with LRYGB include anastomotic leak, stricture, or bleeding, gastric remnant dilation, pouch dilation, nutritional and metabolic derangements, internal hernia, cholelithiasis, and marginal ulceration. The bypass procedure carries a mortality rate of 0% to 3.3% and is associated with 50% to 80% loss of excess weight.

Procedure’s effect on diabetes

We examined the literature, emphasizing these two operations, with regards to their effects on diabetes. Very few randomized prospective studies that compare the two procedures exist. Such trials are difficult to perform as the two procedures differ markedly in invasiveness and reversibility. Angrisani and colleagues performed such a trial, randomizing 51 patients to either LAGB or LRYGB. The young patient population they studied, however, did not contain enough patients with diabetes to evaluate which bariatric procedure proved more beneficial to its resolution.

Most studies comparing the two procedures have been matched-pair studies with prospectively collected data. In a well-designed study, Cottam and colleagues compared LAGB with LRYGB by following 181 matched pair patients over three years. They reported 78% resolution of type 2 diabetes in the LRYGB group vs. 50% in the LAGB group. Insulin resistance resolved in 94% of LRYGB patients vs. 56% in the LAGB group.

Researchers with several studies have retrospectively examined the outcomes of these two operations with respect to type 2 diabetes remission or improvement. Tice and colleagues recently published a systematic literature review of 14 comparative studies comparing the two procedures. Per their review, type 2 diabetes rates of remission in LAGB patients ranged between 40% and 77%; in RYLGB patients, remission rates of 72% to 100% were seen. Smith and colleague examined long-term data and found type 2 diabetes rates of remission in LAGB to be between 45% and 80% (45% at four years postoperative follow-up); in RYLGB patients, rates of remission between 74% and 89% were seen (89% at 10 year postoperative follow-up). Dixon and colleagues compared conventional weight loss therapy with LAGB in a recent randomized controlled trial. Of the 55 patients that completed their study, remission of type 2 diabetes was seen in 73% of the surgical group compared with 13% in the conventional-therapy group. This represents the first randomized trial to demonstrate these findings.

Benefits of surgery

Many studies have shown that all major bariatric procedures are effective in achieving weight loss and remission or improvement of type 2 diabetes, as well as other comorbid conditions. Rates of remission or improvement with type 2 diabetes vary significantly between studies, but a consistent trend is seen favoring LRYGB as a more efficacious procedure for diabetes management.

Whether the higher remission rate of diabetes with LRYGB is due to its overall greater weight loss or due to changes in foregut hormonal physiology remains unclear; evidence exists to support both proposed mechanisms. The true mechanism may be a combination of the short-term changes produced by caloric restriction and bypass of the foregut with its associated changes in the entero-insular hormone axis, coupled with long-term overall weight loss. Current research about GIP, GLP-1, ghrelin, and adipocytokine function in the surgical patient with diabetes may clarify this in the future.

Based upon available data, LRYGB appears to be the better procedure for treatment of diabetes in morbidly obese patients. Long-term outcome results for LAGB are not yet available. As with many surgical procedures, designing randomized, controlled trials directly comparing them is difficult to do, and at this time our opinion is mostly informed by well-designed matched cohort studies.

LAGB and LRYGB are very different in their invasiveness, mechanism of weight loss and risk profiles. Making a universal recommendation of one procedure over the other is problematic. After an informed discussion between patient and surgeon, each patient must make an individual risk-benefit consideration before making a choice. While LAGB may be more appropriate for some patients, LRGYB is clearly the better bariatric operation for treatment of type 2 diabetes if the patient has an acceptable surgical risk.

Bariatric surgery should be discussed and offered early to morbidly obese patients who suffer from type 2 diabetes. Earlier intervention offers a chance to preserve beta-cell mass and function, increasing the chance of halting progression and achieving remission or cure of type 2 diabetes with bariatric surgery. Convincing data exist to shift the paradigm from “should we operate for morbid obesity and diabetes?” to “which operation should be performed?” Our current data suggests that LRGYB should be this operation. Do we have the magic bullet yet? Not quite, but we are getting closer.

Saurabh Khandelwal, MD, is an Acting Instructor and Senior Fellow in the Center for Videoendoscopic Surgery in the Department of Surgery at the University of Washington, Seattle.

Brant Oelschlager, MD, is an Associate Professor and Director of the Center for Videoendoscopic Surgery, Director of the Swallowing Center and Director of Bariatric Surgery in the Department of Surgery at the University of Washington, Seattle.

For more information:

• Angrisani L. Surg Obes Relat Dis. 2007;3:127-132.
• Buchwald H. JAMA. 2004:292;1724-1737.
• Cottam DR. Obesity Surgery. 2006;16:534-540.
• Dixon JB. JAMA. 2008;299:316-323.
• Freedman DS. JAMA. 2002;288:1758-1761.
• Gumbs AA. Obesity Surgery. 2005;15:462-473.
• Long S. Diabetes Care. 1994;17:372-375.
• Meneghini LF. Cell Biochem Biophys. 2007;48:97-102.
• Pories WJ. Ann Surg. 1995;222:339-350.
• Smith BR. Endocrinol Metab Clin N Am. 2008;37:943-964.
• Tice JA. Am J Med. 2008;121:885-893.