For super-obese patients, duodenal switch beats gastric bypass

September 22, 2006

In the first large, single-institution series directly comparing weight-loss outcomes in super-obese patients, researchers from the University of Chicago found that a newer operation, the duodenal switch, produced substantially better weight-loss outcomes than the standard operation, the Roux-en-Y gastric bypass.

In the October issue of the Annals of Surgery, the researchers report that the duodenal switch (DS) produced greater weight loss than the Roux-en-Y gastric bypass (RYGB) by all measures in patients with a body mass index (BMI) of at least 50. These patients typically carry at least 150 pounds more than their ideal weight.

In this study, patients undergoing duodenal switch were significantly more likely to achieve and maintain successful weight loss--defined as losing more than half of their excess weight--at one year (DS 83.9% vs. RYGB 70.4%) and three years (DS 84.2% vs. RYGB 59.3%) after surgery.

"While there is no single ideal bariatric procedure that can be applied to all severely obese patients, we have generally recommended the duodenal switch for those with a BMI greater than 50," said study author Vivek Prachand, MD, assistant professor of surgery at the University of Chicago. "This study confirms that approach. Both procedures appear to be reasonably safe in the hands of an experienced team, but the duodenal switch appears to offer a considerable advantage in terms of the amount and possibly the duration of weight loss."

The super obese make up only a fraction of the U.S. obesity pandemic, but their ranks are increasing faster than any other group. When the term was coined in 1987, fewer than one in 2,000 adults in the United States met the criteria of a BMI greater than 50. (A normal BMI is 18.5 to 24.9. From 25 to 29.9 is considered overweight. Thirty or above is considered obese; 40 and above is morbidly obese.) The prevalence of the super-obese has quintupled since then, to one in 400 U.S. adults in 2000, which adds up to more then 50,000 people in the U.S.

At the same time, bariatric or weight-loss surgery has increased from about 16,000 cases in 1992, to 63,000 in 2002, to 171,000 in 2005. The most common surgical procedure for these patients--more than 80 percent of all bariatric operations in 2002--is the gastric bypass, which involves stapling off a large portion of the stomach to make overeating difficult, and rerouting the intestines to reduce the absorption of calories. The duodenal switch--fewer than eight percent of all bariatric procedures performed nationwide--leaves a slightly larger stomach pouch but makes even more drastic alterations to the intestines to limit absorption, particularly of fats and starches.

This study involved 350 consecutive super-obese patients who underwent weight-loss surgery at the University of Chicago Hospitals between Aug. 5, 2002, and Nov. 10, 2005. One hundred ninety-eight patients underwent duodenal switch and 152 had a gastric bypass. More than 80 percent of both groups were female. The average age was 40, but that ranged from 18 to 68. About 92 percent had the surgery performed laparoscopically, through small abdominal incisions.

The duodenal-switch patients were slightly heavier. Their average weight before surgery was 368 pounds, compared to 346 for gastric-bypass patients. Average BMIs were also higher: 58.8 for the duodenal-switch patients (up to 96.3), compared to an average BMI of 56.4 for gastric-bypass patients (up to 84.2).

On average, patients who had a duodenal switch stayed in the hospital one day longer, four days instead of three. About 24 percent of DS patients stayed more than four days and about 20 percent of RYGB patients stayed more than three days. There was one death among the 198 duodenal-switch patients within 30 days of the operation and no deaths before 30 days among 152 gastric-bypass patients.

The duodenal switch produced greater weight loss. DS patients lost more total weight and a larger percentage of excess body weight and consequently had a bigger decrease in BMI. When they were weighed one year after surgery, DS patients had lost an average of 149 pounds compared to 121 pounds for RYGB patients. After three years, DS patients had lost 173 pounds, but average weight loss for RYGB patients had decreased to 118 pounds.

"Every one of these patients had significant weight loss," Prachand said, "but the duodenal-switch patients had greater weight loss and seemed to keep the weight off longer."

"There has been a perception amongst bariatric surgeons that the duodenal switch might provide better weight loss than gastric bypass in super-obese individuals," said Prachand. Several studies have demonstrated higher rates of weight-loss failure and weight regain following gastric bypass in these patients.

But surgeons have been hesitant to adopt the duodenal switch for several reasons, he said: "greater technical complexity of the operation, particularly when performed laparoscopically; greater potential for nutritional deficiencies; and need for life-long medical follow-up."

"Given these concerns," he said, "it would be difficult to recommend duodenal switch without demonstrating a significant advantage over the gastric bypass, which is generally a very effective operation in severely obese patients. Our study demonstrates an advantage with regards to weight loss."

"We still need longer-term data on these patients," he added. "We are currently comparing nutritional outcomes and improvement in obesity-related medical problems, including type 2 diabetes, high blood pressure, elevated cholesterol levels, acid reflux, and obstructive sleep apnea in these patients. We don't know yet how much weight loss we need to get those health benefits, but losing more of the excess weight certainly seems to be better."

Additional authors of the study were John Alverdy and Roy DaVee of the University of Chicago.