An unusual peritoneal fossa: anatomic report and clinical implications.

The peritoneal fossae are usually related to rotation and adhesion of the abdominal viscera to the posterior abdominal wall during fetal development, and/or the presence of retroperitoneal vessels running just under the peritoneum and raising serosal folds. These fossae, therefore, are regarded as congenital and have been considered clinically and surgically as sites of internal abdominal hernias. The authors describe a peritoneal fossa interposed between the fourth portion of the duodenum and the abdominal aorta. Due to a scoliosis of the lumbar column, the abdominal aorta had shifted to the left of the duodenum, stretching two semilunar avascular peritoneal folds connecting the vessel with the ascending duodenum. These two folds bounded above and below an entrance into a fossa lined by the posterior parietal peritoneum and bordered by the fourth portion of the duodenum on the right and the aorta on the left. This recess extended as far as the anterior surface of the second and third lumbar vertebrae. On the basis of the anatomic findings, the authors suggest that acquired fossae, because of their size and topography, may play a part in the etiopathogenesis of internal abdominal hernias.