Abdomen:Visceral arteries:Renals

**Renal Arteries**

* Kidney is supplied by 1 renal artery in most individuals
	+ Renal artery usually 5-6 mm in diameter, 4-6 cm long
	+ 30-40% incidence of multiple renal arteries
		- More common on right side if present
* Renal arteries arise from abdominal aorta at L2 level
	+ Right renal artery arises anterolaterally from aorta
		- Slightly longer than left renal artery
		- Courses posterior to both inferior vena cava (IVC) and right renal vein
	+ Left renal artery arises laterally from aorta
		- Courses posterior to corresponding renal vein
	+ Main renal arteries divide at renal hilum into anterior and posterior segmental arteries

* Intrarenal Arterial Anatomy
	+ Anterior segmental artery supplies upper, middle, and lower segments of kidney
		- Usually also supplies apical segment
	+ Posterior segmental artery usually supplies only posterior segment of kidney
		- May supply apical segment in minority of patients
	+ Segmental arteries yield interlobar arteries
		- Course alongside renal pyramids toward periphery
		- Yield arcuate arteries at corticomedullary junction
			* Arcuate arteries travel across top of renal pyramids and give rise to interlobular arteries
			* Interlobular arteries are tiny parenchymal branches that course toward kidney surface and subdivide into afferent glomerular arterioles

Branches of Renal Arteries

* **Inferior adrenal artery**
	+ Arises superiorly from proximal main renal artery
		- Supplies inferior aspect of adrenal gland
		- Adrenal gland is also supplied by superior adrenal artery (abdo aorta) and middle adrenal artery (inferior phrenic artery)
* **Superior capsular artery**
	+ Arises adjacent to, or with, inferior adrenal artery
	+ Primarily supplies perirenal (capsular) fat
	+ May anastomose with retroperitoneal arterial plexus
		- Plexus is derived from several tiny aortic branches
	+ Communicates with intrarenal arteries via perforating branches
* **Middle capsular artery**
	+ Arises from main renal artery or its branches
		- Medial course toward renal sinus; gives off branches that supply ventral and dorsal perirenal fat
		- Perforating middle capsular arteries arise from renal interlobular arteries, penetrate capsule, and anastomose with perirenal branches
* **Inferior capsular artery**
	+ Commonly arises from gonadal artery
	+ When present, anastomoses with superior capsular artery; forms arcade along lateral margin of kidney
		- Arcade communicates with perforating capsular arteries and other retroperitoneal arteries
* Capsular arteries may provide collateral flow to kidney
	+ Occurs with severe renal artery stenosis/occlusion located distal to capsular artery origin
	+ Exophytic renal neoplasms may derive portion of arterial supply from these vessels
		- e.g., angiomyolipoma, renal cell carcinoma
* **Ureteric arteries**
	+ Superior ureter is supplied by branches arising from renal, inferior adrenal, or testicular artery
	+ Distal ureter is supplied by tiny branches from common, internal, and external iliac arteries
	+ May provide collateral flow to kidneys in presence of renal artery stenosis/occlusion
		- Enlarged collaterals may cause "ureteral notching"

Variant Renal Arterial Anatomy

* 30-40% incidence of variations in number, location, and branching patterns of renal arteries
	+ Accessory renal arteries usually arise from aorta
		- May arise from common iliac arteries
		- Rarely arise above superior mesenteric artery (SMA)
* Horseshoe kidneys always have multiple renal arteries
	+ Fused portion of horseshoe kidney (isthmus) may be supplied by distal aorta and iliac arteries
* Other congenital variations in renal configuration/position (e.g., pelvic kidney, crossed fused ectopia) have high incidence of variant arterial anatomy