Anatomy of Adipose Compartments and Fascial Structures in the Posterolateral Region of the Kidney With Special Focus on the Thin Adipose Compartment.

objectivesTo anatomically and histologically define the adipose and fascial structures posterior and lateral to the kidney and propose a compartment-based anatomical model aligned with intraoperative observations.

methodsSeven cadavers were used for macroscopic and histological analyses. In the macroscopic analysis, the spatial relationships between the perirenal fat (PeRF), pararenal fat, posterior renal fascia (PRF), and extraperitoneal fascia (EPF) were examined. Histological observations focused on the distribution and continuity of adipose compartments and the organization of the surrounding dense fibrous connective tissue.

resultsMacroscopically, the EPF covered the anteromedial pararenal fat and extended posteriorly to the kidney. Upon incision, a small amount of adipose tissue was observed directly beneath it. Removing this TAC exposes the peritoneum and PRF with a clear demarcation between them. Histological analysis confirmed that the posterior renal and EPF were distinct, with dense connective tissue structures enclosing a separate TAC. This compartment extended anteriorly between the PeRF and peritoneum, and laterally between the peritoneum and EPF. These extensions converge near the peritoneal reflection in the lateral renal region, forming a characteristic triradiate configuration of adipose tissue.

conclusionsOur findings challenge the classical notion that the renal fascia is a single continuous layer, supporting a compartment-centered anatomical model. The posterior and lateral regions of the kidney contain a distinct third adipose compartment, bordered by the posterior renal and extraperitoneal fasciae. This model offers improved anatomical clarity and may aid understanding during laparoscopic, retroperitoneoscopic, and robot-assisted surgeries.