title: Internal Herniation After Laparoscopic Roux-en-Y Gastric Bypass Surgery: Pitfalls in Diagnosing and the Introduction of the AMSTERDAM Classification.
abstract: Internal herniation (IH) probably is the most elusive complication of laparoscopic Roux- en-Y gastric bypass (LRYGB) surgery. This study provides a definition for IH, a diagnosing algorithm, and information on several factors influencing IH formation.
  
  
  
  Baseline characteristics, laboratory findings, imaging studies, operative findings, and follow up data of 1583 patients that underwent LRYGB at our bariatric facility between 2007 and 2013 were recorded. Follow up varied between 3 and 76 months, and 85 % of the data was available for analysis at 12 months. Our surgical technique was standardized. Intermesenteric spaces were not closed until July 2012, where after they were closed. To facilitate comparison, IH cases were matched with controls.
  
  
  
  Forty patients (2.5 %) had an IH during re-laparoscopy. The modal clinical presentation is acute onset epigastric discomfort, often crampy/colicky in nature. Additional examinations included laboratory testing, abdominal X-ray, abdominal ultrasound, and abdominal CT scanning. Patients who developed an IH lost a significantly higher percentage of their total body weight than their matched controls at every time point. IH incidence was higher in the non-closure group than the closure group.
  
  
  
  The large variation in reported IH incidence is due to the large variation in IH definition. To gain more uniformity in reporting IH prevalence, we propose the use of the AMSTERDAM classification. Post-LRYGB patients with acute onset crampy/colicky epigastric pain should undergo abdominal ultrasound to rule out gallbladder pathology and offered re-laparoscopy with a low threshold. IH incidence is highest among patients with rapid weight loss and non-closure of intermesenteric defects.
authors.affiliation: Department of Metabolic and Bariatric Surgery, Slotervaart Hospital, Louwesweg 6, 1066 EC, Amsterdam, The Netherlands. ngeubbels@gmail.com.
authors.forename: Noëlle
authors.initials: N
authors.lastname: Geubbels
authors.affiliation: Department of Metabolic and Bariatric Surgery, Slotervaart Hospital, Louwesweg 6, 1066 EC, Amsterdam, The Netherlands.
authors.forename: Eveline A
authors.initials: EA
authors.lastname: Röell
authors.affiliation: Department of Metabolic and Bariatric Surgery, Slotervaart Hospital, Louwesweg 6, 1066 EC, Amsterdam, The Netherlands.
authors.forename: Yair I Z
authors.initials: YI
authors.lastname: Acherman
authors.affiliation: Department of Metabolic and Bariatric Surgery, Slotervaart Hospital, Louwesweg 6, 1066 EC, Amsterdam, The Netherlands.
authors.forename: Sjoerd C
authors.initials: SC
authors.lastname: Bruin
authors.affiliation: Department of Metabolic and Bariatric Surgery, Slotervaart Hospital, Louwesweg 6, 1066 EC, Amsterdam, The Netherlands.
authors.forename: Arnold W J M
authors.initials: AW
authors.lastname: van de Laar
authors.affiliation: Department of Metabolic and Bariatric Surgery, Slotervaart Hospital, Louwesweg 6, 1066 EC, Amsterdam, The Netherlands.
authors.forename: L Maurits
authors.initials: LM
authors.lastname: de Brauw
mesh_terms: D015746:Abdominal Pain / Q000209:etiology; D000328:Adult; D016022:Case-Control Studies; D003661:Decision Support Techniques; D005260:Female; D015390:Gastric Bypass / Q000009:adverse effects* / Q000379:methods; D046449:Hernia, Abdominal / Q000145:classification / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000209:etiology; D006801:Humans; D015994:Incidence; D010535:Laparoscopy / Q000009:adverse effects / Q000379:methods; D008297:Male; D009426:Netherlands; D009767:Obesity, Morbid / Q000601:surgery*; D011183:Postoperative Complications / Q000145:classification / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000209:etiology; D012189:Retrospective Studies; D012720:Severity of Illness Index; D014057:Tomography, X-Ray Computed
keywords: Classification; Complication; Internal herniation; Laparoscopic Roux-en-Y gastric bypass; Morbid obesity; Small bowel obstruction