Transmesosigmoid small bowel herniation, an unusual cause of obstruction F. Cherbanyk , M. Dimitrief, E. Pezzetta, F. Barros, O. Martinet Service de Chirurgie Hôpital RIVIERA-CHABLAIS site Montreux Introduction : internal hernia are rare, heterogeneous but well known cause of small bowel obstruction ; different types of hernia have been recognized and clearly described, among them we should keep in mind the unusual transmesenteric variants.   Methods : in the following report we wish to illustrate the case of a healthy young patient who presented with overt small bowel obstruction related to an internal transmesosigmoidal hernia. We would like here to emphasize particularly on the role of the preoperative CT Scan and on the laparoscopical approach. Case presentation: a 48-years-old woman presented to our emergency room complaining of intense colicky lower abdominal pain and repeated vomiting. Physical examination revealed tenderness of the hypogastrium and left iliac fossa without overt peritonism. A CT Scan was performed and showed a dilated, prominent and thickened small bowel loop located in the left iliac fossa near to the sigmoid colon with a small amount of free fluid and local infiltration. The hypothesis of an internal hernia was mentioned and definitively retained and the patient was therefore submitted to an early laparoscopical exploration. During the procedure an internal hernia with protrusion of a small bowel loop through a defect in the sigmoid mesocolon was noticed. The hernia was reduced and the defect was closed without need of enteral resection.   axial and coronal CT Scan images showing 1) small bowel obstruction and 2) an abnormal cluster of small bowel loops located posteriorly and medially to the sigmoid colon suggestive of a transmesenteric herniation Conclusions : early and prompt suspicion and recognition of internal hernias with subsequent surgical management is mandatory in these unusual situations ; laparoscopic exploration and treatment is a valid, less invasive and attractive option in this respect.