['Internal hernia (IH) is one of the more acute and potentially devastating complications after laparoscopic gastric bypass (LGB). Currently, there is no way to predict which patients will develop IH. We propose that patients who undergo periods of rapid excess weight loss (EWL) following LGB are more likely to develop IH.', 'A retrospective review of a prospectively collected laparoscopic gastric bypass database from our bariatric center was performed. Patient data between 2002 and 2009 was reviewed. Demographics, initial body mass index (BMI), detailed weight loss curves, and morbidity, specifically IH, were reviewed. Statistical analysis was performed. Logistic regression analysis was used to obtain an adjusted odds ratio for rapid weight loss and hernia development.', "We reviewed all 934 LGB procedures performed. The average initial BMI was 49.1 kg/m2 (range=34-91 kg/m2). EWL based on our current averages at 1, 3, 6, 9, and 12 months postoperatively were 20, 40, 60, 75, and 85%. We statistically defined rapid EWL as greater than the 90th percentile for weight loss. Rapid EWL was noted in 33.2% (310/934) of patients. Fifty-eight (6.2%) patients were identified with IH. Of these, 27(46.5%) had periods of rapid EWL (odds ratio [OR]=1.83; 95% CI=1.07, 3.02). Bivariate analysis of patient factors that led to rapid EWL identified initial BMI (49.3 vs. 46.6 kg/m2) and rapid EWL as increasing the likelihood of developing IH (p=0.026). A multivariate logistic model for IH identified only rapid EWL as a predictive factor. Locations of IH were the jejunojejunostomy (24), Pedersen's defect (23), adhesions (9), and colonic mesentery (1). There were five patients with combined JJ and Pederson's hernias."] Does rapid excess weight loss following laparoscopic gastric bypass lead to increased risk of internal hernia?