Roux-Y Gastric Bypass Increases Risk of Exocrine Pancreatic Insufficiency

Several prior studies have noted that Roux-Y gastric bypass surgery often leaves patients with exocrine pancreatic insufficiency, but new research from Switzerland indicates that different flavors of the procedure expose patients to greatly different risks.

Investigators followed 188 consecutive patients who underwent either distal Roux-Y surgery (common channel <120cm, biliopancreatic limb 80-100cm) or proximal Roux-Y surgery (alimentary limb = 155cm, biliopancreatic limb 40-75cm) for at least 2 years (mean follow-up, 52.2 months) and found significant differences in the eventual prevalence of exocrine pancreatic insufficiency.

Just 79 patients (42% of the total study population) underwent distal Roux-Y gastric bypass surgery, but such patients accounted for 38 of the 59 cases of pancreatic insufficiency that researchers found during the follow-up period. Only 21 of the 109 patients who underwent proximal Roux-Y surgery went on to develop the condition.

“The prevalence of exocrine pancreatic insufficiency after distal Roux-Y gastric bypass (48%) and proximal Roux-Y gastric bypass (19%) is of clinical importance (p<0.01),” the investigators wrote in Surgery for Obesity and Related Diseases. “There was no significant difference in absolute or relative limb lengths between exocrine pancreatic insufficient and non-insufficient groups after distal Roux-Y gastric bypass.”

None of the patients in the study had a history of gastrointestinal or hepatobiliary resection, except for cholecystectomy. Also excluded from the final results were patients who became pregnant after their operations and patients who underwent any revision of their Roux-Y gastric bypasses.

The investigators noted a significant difference between distal and proximal groups in initial body mass index. Patients who underwent distal surgery began at 47.1±8.1kg/m²; patients who underwent proximal surgery began at 42.7±6.1kg/m² (p<0.01). Distal patients were also more likely than proximal patients to begin with Obesity Surgery-Mortality Risk Scores that put them in group C (13% vs. 3%; p=0.02).

The investigators diagnosed exocrine pancreatic insufficiency using a combination of clinical symptoms and test results: fecal pancreatic elastase-1 (PE-1) <200μg/g stool or a fecal PE-1 measurement between 200 and 500 μg/g stool plus a positive de-challenge/re-challenge test with pancreatic enzyme replacement therapy. The mean delay between surgery and the onset of pancreatic insufficiency was 12.5 months, but timing varied greatly. The standard deviation for onset delay was 16.3 months.

The link between Roux-Y surgery and exocrine pancreatic insufficiency was observed long ago. Indeed, a primary aim of the surgery is to induce the body to digest many of its own pancreatic enzymes before those enzymes come into contact with food, so, in many ways, the effects of a successful surgery mimic a mild degree of pancreatic insufficiency.

A small amount of prior research has compared the risk of exocrine pancreatic insufficiency after Roux-Y and other methods of gastric bypass. A German study, for example, noted that Roux-Y was more likely to produce pancreatic insufficiency than Longmire-Gutgemann reconstruction — at least in Wistar rats.

“The production of enzymes is changed after both operations,” the study authors wrote in Acta chirurgica Hungarica. “The pH optimum as well as the viability of the protein enzymes is shifted. Since the changes are more pronounced after Roux-Y operation signs of pancreatic insufficiency should be expected more frequently after this operation.”

The new study, however, appears to be the first to compare the risk of pancreatic insufficiency associated with different types of Roux-Y surgery.