Small bowel obstruction caused by an unusual variant of paraduodenal hernia. The "middle congenital mesocolic hernia": case report.

Internal hernias account for 0.2-0.9 % of all small bowel obstructions and are associated with a mortality rate of 50 % when strangulation is present. Congenital mesocolic hernias, traditionally called paraduodenal hernias, caused by an abnormal rotation of the primitive midgut, are the most common type of internal hernia. They can be divided into three types: the right and the left congenital mesocolic hernias, accounting for the 25 and 75 % of all cases, respectively, and the extremely rare transverse congenital mesocolic hernia. A high preoperative misdiagnosis rate has been reported and a surgical exploration is recommended to identify strangulation. The present case report describes a case of small bowel obstruction due to an unusual variant of congenital mesocolic hernia never previously reported in the literature. We discuss the clinical appearance, pathogenesis, diagnosis, and treatment of the case, with a brief review of the literature focused on the pathogenesis and management of mesocolic congenital hernias.