Does the length of bypassed bowel during distal gastric bypass affect weight loss?

Weight recurrence (WR) affects > 20% of patients following Roux-en-Y gastric bypass (RYGB). Shortening of the common channel (CC) after RYGB (distal bypass) has been proposed for additional weight loss in patients with WR, but results vary, and concerns for vitamin deficiencies/malnutrition exist. Our aim was to determine whether the percentage of bowel bypassed after distal bypass is associated with the amount of postoperative weight loss.

Patients undergoing distal bypass between 2018 and 2022 were reviewed. Small bowel limb lengths before and after distal bypass were measured, and the percentage of bypassed bowel was calculated (= bypassed biliopancreatic limb/total small bowel length). Patients were dichotomized into two groups based on the percentage bypassed bowel (≤ 50% vs. > 50%). Weight loss (measured as excess BMI loss; EBIL%), comorbidities resolution, complications, and nutritional deficiencies were reviewed.

Thirty female patients underwent distal bypass during the study period. After distal bypass, the Roux was lengthened to 150 cm (75-175 cm) from 75 cm (20-200 cm), and the CC shortened to 150 cm (100-310 cm) from 510 cm (250-1000 cm). These changes resulted in an increase in the size of the bypassed biliopancreatic limb from 40 cm (15-90 cm) to 330 cm (180-765 cm) and a total alimentary limb (TALL; Roux + CC) shortening from 590 cm (400-1075 cm) to 300 cm (250-400 cm). The group with > 50% bowel bypassed had higher EBIL%. Overall EBIL% was 36.9 ± 14.7%, 53.3 ± 25.6%, and 62.1 ± 36.9% at 0.5, 1, and 2 years, respectively. There were minimal vitamin deficiencies. Diabetes resolved in 100% (n = 3/3), HTN in 67% (n = 10/15), and GERD in 73% (n = 11/15). Complication rate was 23%. No reintervention for malnutrition or vitamin deficiencies was required.

Distal bypass effectively leads to considerable weight loss and comorbidity improvement in patients with WR after RYGB, but the amount of weight loss depends on the percentage of bypassed bowel. An exact threshold of bypassed bowel that optimizes weight loss outcomes and simultaneously minimizes the nutritional complications needs to be determined. Meanwhile, close monitoring for vitamin deficiencies is recommended.