The renal arteries are paired arteries that supply the kidneys with blood. Each is directed across the crus of the diaphragm, so as to form nearly a right angle. The renal arteries carry a large portion of total blood flow to the kidneys. Up to a third of total cardiac output can pass through the renal arteries to be filtered by the kidneys. Structure The renal arteries normally arise at a 90° angle off of the left interior side of the abdominal aorta, immediately below the superior mesenteric artery. They have a radius of approximately 0.25 cm, 0.26 cm at the root. The measured mean diameter can differ depending on the imaging method used. For example, the diameter was found to be 5.04 ± 0.74 mm using ultrasound but 5.68 ± 1.19 mm using angiography. Due to the anatomical position of the aorta, the inferior vena cava, and the kidneys, the right renal artery is normally longer than the left renal artery. The right passes behind the inferior vena cava, the right renal vein, the head of the pancreas, and the descending part of the duodenum. It’s somewhat lower than the left one. Left artery lies behind the left renal vein, the body of the pancreas and the splenic vein, and is crossed by the inferior mesenteric vein. Branches Before reaching the hilus of the kidney, each artery divides into four or five branches. The anterior branches (the upper, middle, lower and apical segmental arteries) lie between the renal vein and ureter, the vein being in front, the ureter behind. The posterior branches, which are fewer in number and include the posterior segmental artery, are usually situated behind the ureter. Each vessel gives off some small inferior suprarenal branches to the suprarenal gland, the ureter, and the surrounding cellular tissue and muscles. One or two accessory renal arteries are frequently found, especially on the left side since they usually arise from the aorta, and may come off above (more common) or below the main artery. Instead of entering the kidney at the hilus, they usually pierce the upper or lower part of the organ. Variation The arterial supply of the kidneys is variable and there may be one or more renal arteries supplying each kidney. It is located above the renal vein. Supernumerary renal arteries (two or more arteries to a single kidney) are the most common renovascular anomaly, occurrence