Distal small bowel bypass for weight regain after gastric bypass: Safety and efficacy threshold occurs at<70% bypass

Background For patients with poor weight loss (WL) after Roux-en-Y gastric bypass (RYGB) there are few well-tolerated and effective surgical options. Revision to distal bypass by shortening of the common channel (CC) induces significant WL but often produces protein calorie malnutrition (PCM) and severe diarrhea. Objective The aim of this study was to identify a safe and effective threshold for distal small bowel bypass when done for revision of gastric bypass. Setting Academic Institution, United States. Methods We performed revision of RYGB for WL in 20 patients by shortening the CC to a new length of 120-300 cm. The Roux limb length was unchanged. WL and PCM were monitored. A threshold for percent of small bowel bypassed at which PCM was avoided was retrospectively determined. WL was then compared in patients above and below this threshold. Five patients completed a 250-kcal mixed meal challenge before and 3 months after revision to determine selected gut hormone responses. Results Bypassing≥70% small bowel resulted in PCM in 4 of 10 patients but in none of 10 patients below that threshold. PCM was observed as late as 2 years after revision and necessitated rerevision by lengthening of the CC in 3 patients. Additionally, nocturnal diarrhea was more common and more intractable when≥70% bypass was done. Both groups had significant excess body WL over 2 years, but it was greater in patients with≥70% bypass (47±19 versus 26±17; P<.05). A favorable gut hormone response was observed with 3-hour decrease in glucose-dependent insulinotropic peptide (GIP) by 25% and increase in glucagon-like peptide-1 (GLP-1) by 25%, whereas fasting peptide-YY (PYY) increased by 71% (P<.05 for all). Conclusions Revision of RYGB to distal bypass when it is<70% of a patient's small bowel length results in an acceptable balance of WL and a positive safety profile. WL may be mediated through an enhanced gut hormone effect, an aversion to ingested fat, and possibly other mechanisms.