hilus

Hilus (plural hila) is an anatomical term for a region on an organ where structures such as blood vessels, nerves, ducts, or lymphatics enter and exit. The term is Latin in origin and is used to describe several distinct entrances across organ systems. The hilum is typically a groove, notch, or recessed area on the visceral surface.

In the lungs, the hilum is the medial root of each lung, containing the main bronchus, pulmonary arteries and veins, and accompanying nerves and lymphatics. The arrangement forms the lung's vascular and airway connections to the mediastinum.

In the kidneys, the renal hilum is the concave, medial border where the renal artery, renal vein, and ureter pass into or out of the kidney, along with accompanying lymphatics and nerves. It is the gateway for the kidney’s vascular supply and drainage and for urine flow to the ureter.

In the spleen, the splenic hilum is the indented area on the visceral surface through which the splenic artery and splenic vein enter and exit.

In lymph nodes and other organs, hiluses denote similar entrance or exit points for vessels and ducts. Clinically, the size, contour, or appearance of a hilum on imaging can aid in diagnosing pathology such as tumors, inflammation, or vascular congestion, particularly in the chest and abdomen.