ANATOMY OF THE RETROPERITONEUM - OBSERVATIONS OF THE DISTRIBUTION OF PATHOLOGICAL FLUID COLLECTIONS

PURPOSE: To correlate anatomic dissections with clinical observations regarding anatomic distribution of retroperitoneal fluid, and to docum ent the existence of planes that lie between classically described ret roperitoneal-spaces. MATERIALS AND METHODS: Latex was injected in vary ing amounts into the pancreatic tail in three fresh cadavers to simula te peripancreatic fluid collections. Spiral computed tomography (CT) w as performed of the abdomen and pelvis after each latex injection. Two cadavers were subsequently frozen and sectioned in axial planes; limi ted dissections were performed on these specimens. One was embalmed an d underwent extensive anatomic dissection. Five embalmed, unprepared c adavers were also dissected to confirm observations made in the three prepared cadavers. RESULTS: Latex injected into the tail of the pancre as entered a retromesenteric plane that was posterior to the anterior pararenal space and anterior to the anterior renal fascia. The plane c ontinued superiorly, extending to the diaphragm near the esophageal hi atus; inferiorly, extending to the pelvis along the anterolateral surf ace of the psoas muscle; and laterally, posterior to the descending co lon and its mesentery. The plane also communicated with a retrorenal p lane lying between the posterior renal fascia and the posterior parare nal space. CONCLUSION: Embryologic development of the dorsal mesenteri es suggests the existence of retromesenteric planes, and clinical obse rvations further support their existence. These findings may explain t he observed distribution of retroperitoneal fluid collections from dia phragm to pelvis.