The central aspect of the medial border of each kidney presents with a deep vertical slit that serves as an entry and exit point for the renal blood vessels, ureter, nerves, and lymphatic vessels. This site is known as the hilum of the kidney.

The hilum of the kidney usually projects at the level of the L2 vertebra. However, it depends on the kidney, as the left kidney lies higher than the right one. Therefore, the hilum of the left kidney might already be positioned at the level of the L1 vertebra.

There is a particular order in which structures entering and leaving the kidney are usually situated - the most anterior structure is the renal vein (Read more!), followed by the renal artery (Read more!), behind which is the ureter (Read more!). To memorize this order, keep in mind the abbreviation VAU (“V” goes for the vein, “A” refers to the artery, while “U” is for the ureter).

However, the placement of hilar structures frequently varies. Various case reports have been published on hilar structure arrangement. For instance, branches of both artery and vein might also be placed behind the ureter.

Note: The funnel-shaped flattened superior end of each ureter that leaves the kidney via the hilum is called the renal pelvis (Read more!).

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Hilum of kidneys