Suk-Bae Moon, et al. loop ligation during the loop esophago-jejunostomy to prevent this phenomenon with some success [3]. Howev- er, no clear mechanism for development of blind loop syn- drome or beneficial role of proximal loop ligation during the intestinal bypass procedure has been demonstrated. Migrating motor complex (MMC) describes organized groups of contractions periodically migrating down both the small and large intestine, and has been observed in a variety of animals, including humans [4,5]. MMC is one of the key elements in gastrointestinal motility, and has been known to act as an intestinal house-keeper; periodically cleansing the bowel in preparation for the next meal. Ever since Wood [6] first described the MMC in the isolated mouse colon and Bush et al. [7] described the MMC in the isolated mouse ileum, MMC has been most intensively studied in the mouse model ex-vivo. We hypothesized that the mechanism underlying the stagnation of the intestinal contents in the blind loop syn- drome might be related to changes in MMC, and so we measured the MMCs after creating a side-to-side ileal by- pass anastomosis in a mouse and extrapolated the mecha- nism of the stagnation through the ex-vivo experiments. METHODS Animal treatment Female Institute of Cancer Research mice, aged 8 weeks, were used for the ileal side-to-side anastomosis. The ani- mals were purchased from specific pathogen free labo- ratory animal company (Koatech, Pyeongtaek, Korea). We did not restrict diet and no bowel preparation was per- formed pre-operatively. The mice were anesthetized with a single i.p. dose of tiletamine/zolazepam (Zoletil, Virbac Laboratories, Carros, France) 40 mg/kg. Single s.c. dose of atropine (Daihan Pharm Co., Seoul, Korea) 0.04 mg/kg was administered to decrease the tracheal secretion to pre- vent asphyxia and single i.p. dose of cefmetazole (Daewoong Co., Seoul, Korea) 50 mg/kg was admini- stered. When the absence of a hindlimb pinch-withdrawal reflex was verified, a median laparotomy was performed. After identifying the appendix and ileo-cecal junction, the ileum was traced proximally to locate 4 cm and 8 cm from ileo-cecal junction. After opening the antemesenteric bor- der about 3 mm, side-to-side anastomosis was performed using 10-0 monofilament suture (Ethilon, Ethicon Inc., Sommerville, NJ, USA) under magnifying (x5) surgical loupe. The anterior and the posterior rows were sutured in an interrupted manner for five stitches, respectively (partial bypass model; Fig. 1A). For a total bypass model, the proximal portion of the bypass loop was doubly li- gated to create obstruction with the same suture material, without compromising the mesenteric vascular arcade (Fig. 1B). After completion of the anastomosis, the intes- tine was replaced within the abdomen and the abdomen was closed with 5-0 silk suture. The animals were allowed to recover post-operatively on a heated blanket. Through- out the surgery and recovery the animals were inter- mittently oxygenated with a 97% O2-3% CO2 mixture. Operated animals were sacrificed by CO2 inhalation fol- Fig. 1. Schematic drawing and operative photograph of the partial bypass model (A) and total bypass model (B). In contrast to the partial bypass model, there were no luminal contents within the bypass loop in total bypass model. As such, the diameter of the bypassed loop tended to be greater in the partial bypass model compared to the total bypass model. 252 thesurgery.or.kr