posterior lip of hilum of kidney

The posterior lip of the hilum of the kidney is the margin of renal parenchyma that forms the posterior border of the renal hilum. The renal hilum (or hilus) is the concave, slit-like opening located on the medial surface of the kidney through which the renal artery, renal vein, renal pelvis (ureter), lymphatics, and nerves enter or exit the kidney. This opening is bounded by two raised edges of renal parenchyma the anterior lip and the posterior lip which together frame the hilar aperture.

Anatomical details:

• The hilum leads into the renal sinus, a fat-filled cavity within the kidney that houses the renal vasculature, collecting system, and associated connective tissue. The renal capsule does not cover the sinus, leaving the hilum as the sole opening for these structures to enter and exit.

• The posterior lip specifically refers to the posterior parenchymal ridge that overhangs the hilar opening. It is formed by the posterior portion of the renal cortex and medullary tissue. Because the kidney is oriented with its hilum directed anteromedially, the posterior lip lies slightly more lateral and dorsal relative to the anterior lip.

Clinical relevance:

The distinction between the anterior and posterior lips is important in surgical planning. Tumors or pathology located posteriorly may be more amenable to segmental vascular control via a posterior approach, given the accessibility of the posterior segmental artery behind the posterior lip. Additionally, in cases of renal malrotation, the normal orientation of the lips may be altered for example, the renal pelvis may be found anterior to the renal vessels rather than in its usual posterior position, changing the expected hilar anatomy.