The renal artery is a short paired artery that arises from the lateral aspect of the aorta. Its location is in the retroperitoneum, where it courses laterally towards the hilum of the kidney posterior to the renal veins, nerves and the pancreas. The renal artery gives off several small branches before dividing into its terminal anterior and posterior branches in the hilum of the kidney.
The function of the renal artery is twofold; it supplies the kidney parenchyma with oxygenated blood, and simultaneously delivers the blood to be filtered by eliminating metabolic wastes and excess water and reabsorbing minerals and nutrients.
This article will discuss the anatomy and function of the renal artery.
|Branches||Inferior suprarenal artery; anterior and posterior branches|
|Supply||Kidney, adrenal gland|
The renal artery arises perpendicularly from the abdominal aorta just below the branching of the superior mesenteric artery, roughly at the level of the level intervertebral disc between the L1 and L2 vertebrae.
The right renal artery, which is slightly longer and higher up than the left one, courses posterior to the inferior vena cava, renal vein, head of the pancreas and second part of the duodenum. The left renal artery courses more horizontally and posterior to the renal vein, the body of the pancreas and the splenic vein.
Branches and supply
During its extrarenal course, the renal artery most notably gives off one or more inferior suprarenal arteries. Additionally, the renal artery gives off several unnamed branches for the ureter, perinephric tissue, renal capsule and renal pelvis. It ends near the hilum of the kidney by dividing into an anterior and posterior branch:
- Inferior suprarenal artery: supplies the adrenal gland together with the superior suprarenal artery (arising from the inferior phrenic artery) and middle suprarenal artery (arising from the abdominal aorta).
- Posterior branch: passes behind the renal pelvis and goes on to supply the posterior region of the kidney.
- Anterior branch: further subdivides into segmental arteries that supply the renal vascular segments. It gives off apical, anterior superior, anterior inferior and inferior segmental arteries that each supply their respective segments. Next, the segmental arteries give off lobar branches, usually one for each renal pyramid. Upon reaching the minor calyces, these further subdivide into interlobar arteries, which become arcuate arteries at the base of the pyramids. The arcuate arteries then enter the nephrons as the interlobular arteries, and finally end in the glomerulus as the afferent and efferent arterioles.
Variations in the number, origin and course of renal arteries are quite common. The normal, singular renal artery occurs in about 70% of cases, while an accessory renal artery is present in about 30% of cases. The accessory renal artery most commonly arises just below, or in some cases, above the main renal artery. Rarely, it arises from the coeliac trunk or superior mesenteric artery. The origin of the renal artery can vary, in which one or both may arise from the bifurcation of the aorta or from the common iliac, internal iliac or inferior mesenteric artery. A relatively common variation is also the early branching of the renal artery before it reaches the renal hilum, occuring in about 10% of individuals.
Renal artery stenosis
- Renal artery stenosis is a narrowing of one or both renal arteries. It most commonly occurs bilaterally due to atherosclerosis or fibromuscular dysplasia. The narrowing causes a decrease in renal perfusion, which is wrongly sensed by the kidneys as low blood pressure, causing them to react by increasing the production of renin. Renin triggers the renin-angiotensin-aldosterone response, which in turn increases blood pressure. This reduces the renal artery blood flow even further, creating a vicious cycle of hypertension.