Fascial planes and compartments of the posterior abdomen: The perirenal and pararenal pathways

Our objective was to describe the boundaries and sites of communication of the posterior peritoneal compartments in order to explain extensions of pathological processes in retroperitoneal areas. To this end we examined these distinct bilateral compartments [anterior (AP) and posterior (PP) pararenal and perirenal (P) spaces] in four bodies by CT scans, dissections, crosssections, latex injections, and light microscopy. Perirenal areas bilaterally were closed spaces which extended from the inferior surface of the diaphragm to the superior pelvic aperture (pelvic inlet) tapering superiorly and inferiorly in the shape of two cones with a common base at the midrenal area where they communicated across the median plane. The AP is a potential space on the right but contains the pancreas on the left. Each has shorter superior and inferior extensions than the corresponding PP space. Tough, often multilaminar, fasciae surrounded these spaces and limited the spread of injected latex except where vascular pathways permitted inter‐compartmental spread. Computer‐assisted 3‐D reconstructions showed that these spaces extended potentially from the diaphragm into the pelvis. These compartments and their fasciae help explain the predictable yet restricted clinical extensions of pancreatitis, renal infections, and aortic aneurysms in the posterior abdomen.