What is the identity of Gerota fascia? Histological study with cadavers

Objectives: The advancement of laparoscopic surgery has allowed surgeons to see finer anatomical structures during surgery. As a result, several issues have arisen regarding Gerota fascia that cannot be explained by previous interpretations, such as its various forms observed during surgery. To address these issues, we histologically examined the structure of Gerota fascia.
Methods: Specimens for study were prepared from kidneys with Gerota fascia from four cadavers, and the structure was studied histologically. Its thickness and collagen fiber area ratios were measured using ImageJ and compared to those of the epimysium of the rectus abdominis muscle.
Results: Connective tissue that appeared to be Gerota fascia was observed in 26 specimens. Histologically, the basic structure of Gerota fascia was a sandwich-like structure with a thin layer of thick, long collagen fibers in the central layer, and small granular collagen fibers scattered at the edges. However, not all areas observed had a similar structure; eight specimens were composed only of small granular collagen fibers. The average thickness of the Gerota fascia was 466 μm, and the area ratio of collagen was 27.1%. In contrast, the epimysium was much thicker than Gerota fascia, and its collagen fibers were much thicker and denser.
Conclusions: Gerota fascia, unlike the epimysium, was a very thin and fragile layer of collagen fibers, and its structure was diverse. This explains why Gerota fascia was observed in various states during surgery. It is important for surgeons to understand the properties of Gerota fascia and to treat it appropriately.