AIM: To investigate distal small bowel motility and lipid absorption in patients following elective abdominal aortic aneurysm (AAA) repair surgery.METHODS: Nine patients (aged 35-78 years; body mass index (BMI) range: 23-36 kg/m2) post-surgery for AAA repair, and seven healthy control subjects (20-50 years;BMI range: 21-29 kg/m2) were studied. Continuous distal small bowel manometry was performed for up to 72 h, during periods of fasting and enteral feeding (Nutrison(R)). Recordings were analyzed for the frequency,origin, length of migration, and direction of small intestinal burst activity. Lipid absorption was assessed on the first day and the third day post surgery in a subset of patients using the 13C-triolein-breath test, and compared with healthy controls. Subjects received a 20-min intraduodenal infusion of 50 mL liquid feed mixed with 200 μL 13C-triolein. End-expiratory breath samples were collected for 6 h and analyzed for 13CO2 concentration.RESULTS: The frequency of burst activity in the proximal and distal small intestine was higher in patients than in healthy subjects, under both fasting and fed conditions (P＜0.005). In patients there was a higher proportion of abnormally propagated bursts (71% abnormal), which began to normalize by d 3 (25% abnormal) post-surgery.Lipid absorption data was available for seven patients on d 1 and four patients on d 3 post surgery. In patients,absorption on d 1 post-surgery was half that of healthy control subjects (AUC 13CO2 1323 ± 244 vs 2 646 ±365;P＜ 0.05, respectively), and was reduced to the one-fifth that of healthy controls by d 3 (AUC 13CO2 470 ± 832 vs 2646 ± 365; P＜ 0.05, respectively).CONCLUSION: Both proximal and distal small intestinal motor activity are transiently disrupted in critically ill patients immediately after major surgery,with abnormal motility patterns extending as far as the ileum. These motor disturbances may contribute to impaired absorption of enteral nutrition, especially when intraluminal processing is necessary for efficient digestion.