[Imaging of transmesocolic internal hernias following retrocolic Roux-Y reconstruction: tips and tricks for radiologists].

Among all entities causing intestinal obstruction, internal hernias are rare. However, after retrocolic laparoscopic Roux-Y reconstruction, transmesocolic internal hernias may occur. The loss of mesenteric fat favors the formation of transmesocolic internal hernias, which are the most common type of acquired internal hernias. CT findings of segmental intestinal obstruction are similar in all underlying diseases including peritoneal adhesions, which are the most important differential diagnosis to postoperative internal hernias. Since internal hernias typically alter spatial relationships within the peritoneal cavity, precise analysis of intraperitoneal topography is the most important clue to differentiate internal hernias from peritoneal adhesions. Based on readily identifiable anatomic reference points and structures, so-called landmarks, specific features of internal hernias in CT imaging are outlined. Particular attention is paid to mesenteries, because they define compartments within the peritoneal cavity. Focusing on transmesocolic internal hernias, the anatomy of the mesocolon transversum is described in detail. Finally, we present a checklist facilitating the diagnosis of internal hernias in everyday practice. © Georg Thieme Verlag KG Stuttgart · New York.