Renal Arteries

The renal arteries are paired branches of the abdominal aorta that provide the principal arterial supply to the kidneys. They usually arise from the lateral aspects of the aorta near the L1-L2 vertebral level, slightly inferior to the origin of the superior mesenteric artery.

Each renal artery travels laterally toward the hilum of its respective kidney. Because the abdominal aorta lies to the left of the midline, the right renal artery is usually longer than the left and passes posterior to the inferior vena cava before reaching the right kidney.

Near the renal hilum, each artery divides into branches that ultimately form segmental arteries. These vessels supply anatomically distinct renal vascular segments and behave largely as end arteries, making their arrangement especially important in renal surgery and interventional procedures.

Origin

The renal arteries usually arise from the lateral surfaces of the abdominal aorta.

Their origins are generally located just inferior to the superior mesenteric artery, commonly near the L1-L2 intervertebral region.

Right and Left Renal Arteries

The two renal arteries have different courses because of the asymmetrical positions of the abdominal aorta, inferior vena cava, and kidneys.

Feature	Right Renal Artery	Left Renal Artery
Length	Usually longer	Usually shorter
Course	Passes laterally toward right kidney	Passes laterally toward left kidney
IVC relationship	Passes posterior to inferior vena cava	No comparable crossing behind IVC
Destination	Right renal hilum	Left renal hilum

Right Renal Artery

The right renal artery has a longer course because the abdominal aorta is positioned left of the midline.

It travels toward the right kidney and characteristically passes posterior to the inferior vena cava.

Left Renal Artery

The left renal artery follows a shorter and more direct course from the abdominal aorta to the left renal hilum.

Its relationship to the left renal vein and surrounding retroperitoneal structures is important in renal surgery and vascular imaging.

Relationship to the Superior Mesenteric Artery

The renal arteries typically arise just inferior to the origin of the superior mesenteric artery.

This relationship provides an important landmark on angiography and cross-sectional imaging.

Relationship to the Inferior Vena Cava

The inferior vena cava lies to the right of the abdominal aorta.

Consequently, the right renal artery must pass posterior to the inferior vena cava to reach the right kidney.

Renal Hilum

The renal arteries enter the kidneys through the renal hila, which face generally medially.

The hilum also transmits the renal veins, renal pelvis, lymphatic vessels, autonomic nerves, and surrounding connective tissue.

Arrangement at the Renal Hilum

A commonly described anterior-to-posterior arrangement at the renal hilum is renal vein, renal artery, and renal pelvis.

Branching variations can make the actual arrangement more complex, particularly because arterial branches may divide before reaching the hilum.

Prehilar Branching

The renal artery often divides into major branches before or near the renal hilum.

These branches ultimately give rise to segmental arteries supplying distinct regions of renal parenchyma.

Segmental Arteries

The renal arterial tree is commonly described as supplying five renal vascular segments.

The exact branching pattern is variable, but the segmental organization is clinically important because there is limited collateral circulation between neighboring segments.

Renal Vascular Segments

Segment	General Distribution
Superior, apical	Superior portion of kidney
Anterosuperior	Upper anterior region
Anteroinferior	Lower anterior region
Inferior	Inferior portion of kidney
Posterior	Posterior region of kidney

End-Artery Pattern

The segmental renal arteries function largely as end arteries.

There is relatively little effective collateral circulation between adjacent segmental territories, so occlusion of a segmental artery can produce ischemia in the corresponding region.

Interlobar Arteries

Segmental arteries divide into interlobar arteries, which travel through the renal columns between adjacent renal pyramids.

These vessels pass toward the corticomedullary junction.

Arcuate Arteries

At the bases of the renal pyramids, the interlobar arteries give rise to arcuate arteries.

These vessels arch along the corticomedullary junction.

Interlobular Arteries

The arcuate arteries give rise to cortical radiate arteries, traditionally called interlobular arteries.

These vessels extend outward through the renal cortex and give rise to afferent arterioles.

Afferent Arterioles

The afferent arterioles carry blood into the glomerular capillary networks of renal corpuscles.

Blood then leaves each glomerulus through an efferent arteriole rather than directly through a venule.

Renal Arterial Branching Sequence

Order	Vessel
1	Renal artery
2	Segmental arteries
3	Interlobar arteries
4	Arcuate arteries
5	Cortical radiate, interlobular arteries
6	Afferent arterioles
7	Glomerular capillaries

Glomerular Circulation

Blood entering a glomerulus through an afferent arteriole passes through a specialized capillary tuft where filtration occurs.

The blood exits through an efferent arteriole, creating an unusual arterial-capillary-arterial arrangement.

Efferent Arterioles

Efferent arterioles leaving cortical glomeruli form extensive peritubular capillary networks.

Efferent vessels associated with juxtamedullary nephrons contribute to formation of the vasa recta.

Vasa Recta

The vasa recta are straight vessels that descend into and ascend from the renal medulla alongside loops of Henle.

They participate in maintaining the medullary environment required for urine concentration.

Renal Blood Flow

The kidneys receive a large proportion of cardiac output relative to their size.

This substantial blood flow supports glomerular filtration, regulation of fluid and electrolyte balance, endocrine functions, and metabolic activity.

Relationship to the Renal Veins

Renal venous drainage ultimately converges into the right and left renal veins, which empty into the inferior vena cava.

The venous anatomy differs from the arterial anatomy, particularly because the left renal vein must cross toward the right-sided inferior vena cava.

Left Renal Vein

The left renal vein typically crosses anterior to the abdominal aorta and posterior to the superior mesenteric artery.

This differs from the renal arteries, which arise directly from the aorta and pass laterally toward the kidneys.

Right Renal Vein

The right renal vein is generally shorter because the inferior vena cava lies close to the right kidney.

This contrasts with the right renal artery, which is longer because it originates from the more leftward abdominal aorta.

Renal Arteries and Veins Compared

Feature	Renal Arteries	Renal Veins
Major vessel	Abdominal aorta	Inferior vena cava
Longer vessel	Right renal artery	Left renal vein
Right-sided crossing	Right artery passes posterior to IVC	Right vein has short direct course
Left-sided crossing	Left artery has relatively direct course	Left vein crosses anterior to aorta

Accessory Renal Arteries

Accessory renal arteries are common anatomical variations in which a kidney receives more than one artery directly from the aorta or another nearby vessel.

These additional arteries reflect persistence of embryonic vessels that normally regress during renal development.

Polar Arteries

An accessory renal artery may enter the kidney outside the hilum, particularly at the superior or inferior pole.

Such vessels are often referred to as polar arteries.

Inferior Polar Arteries

An inferior polar artery can cross anterior to the ureter or ureteropelvic junction.

This relationship can be clinically relevant if the vessel contributes to external compression of the urinary outflow tract.

Embryological Basis of Variation

During development, the kidneys ascend from the pelvis toward their adult retroperitoneal position.

They receive successive arterial branches from the aorta during this ascent, and persistence of more than one of these vessels produces accessory renal arteries.

Clinical Significance

Renal Artery Stenosis

Renal artery stenosis is narrowing of one or both renal arteries.

Reduced renal perfusion can activate mechanisms involved in blood pressure regulation and may contribute to renovascular hypertension in appropriate clinical settings.

Atherosclerotic Disease

Atherosclerosis can narrow the renal artery, particularly near its origin from the abdominal aorta.

The anatomical relationship of the renal ostia to the aorta is therefore important during vascular imaging and intervention.

Fibromuscular Dysplasia

Fibromuscular dysplasia can affect the renal arteries and produce characteristic areas of arterial narrowing and dilation.

It is an important non-atherosclerotic cause of renal arterial disease.

Renal Artery Aneurysm

Aneurysmal dilation can occur in the renal arterial system.

Its significance depends on factors such as size, location, morphology, associated symptoms, and patient-specific circumstances.

Renal Infarction

Occlusion of a renal artery or segmental branch can interrupt blood flow to renal tissue.

The limited collateral circulation between segmental territories helps explain the possibility of sharply localized renal infarction.

Renal Transplantation

Renal arterial anatomy is critical in kidney transplantation.

Accessory arteries and early branching patterns must be identified because multiple vessels may require preservation and vascular reconstruction.

Partial Nephrectomy

The segmental organization of renal blood supply is important during nephron-sparing surgery.

Knowledge of the arterial territory supplying a renal region can assist surgical planning and selective vascular control.

Renal Angiography

CT angiography, MR angiography, catheter angiography, and Doppler ultrasound can be used to evaluate renal arterial anatomy.

These methods can demonstrate stenosis, aneurysms, accessory arteries, branching patterns, and other vascular abnormalities.

Endovascular Procedures

Renal arterial anatomy is important during selected angioplasty, stenting, embolization, and other endovascular procedures.

Precise identification of the main and accessory arteries reduces the risk of unintentionally compromising renal tissue.

Relationship to the Ureter

The renal pelvis continues inferiorly as the ureter at the ureteropelvic junction.

Variant lower-pole renal arteries may cross near this region and can alter the local anatomical relationships.

Relationship to the Adrenal Glands

The adrenal glands lie superior and somewhat medial to the kidneys.

Although small branches associated with the renal arteries can contribute to adrenal blood supply through the inferior suprarenal arteries, the adrenal glands receive arterial blood from multiple sources.

Inferior Suprarenal Arteries

The inferior suprarenal arteries commonly arise from the renal arteries.

They contribute to the rich arterial supply of the adrenal glands alongside superior and middle suprarenal arteries.

Relationship to the Abdominal Aorta

The renal arteries are major paired lateral visceral branches of the abdominal aorta.

Their origin lies between the more superior celiac and superior mesenteric arterial origins and the more inferior aortic bifurcation.

Major Relationships

Structure	Relationship
Abdominal aorta	Parent vessel
Superior mesenteric artery	Usually arises slightly superior to renal arteries
Inferior vena cava	Right renal artery passes posterior to it
Kidneys	Principal organs supplied
Renal hila	Entry region for main renal vessels
Adrenal glands	May receive inferior suprarenal branches

Key Anatomical Features

Feature	Key Point
Parent vessel	Abdominal aorta
Type	Paired lateral visceral arteries
Approximate origin	L1-L2 region
Main supply	Kidneys
Longer artery	Right renal artery
Right artery relationship	Passes posterior to inferior vena cava
Major intrarenal branches	Segmental arteries
Collateral circulation	Limited between segmental territories
Common variation	Accessory renal arteries
Clinical importance	Renal perfusion, hypertension, transplantation and renal surgery

Anatomical Importance

The renal arteries are major paired branches of the abdominal aorta and provide the principal arterial supply to the kidneys. They usually arise near the L1-L2 level, just inferior to the superior mesenteric artery, and travel laterally toward the renal hila.

The right renal artery is generally longer and passes posterior to the inferior vena cava, while the left follows a shorter course to the left kidney. Within the kidney, arterial branches form segmental vascular territories before continuing through interlobar, arcuate, cortical radiate, and afferent arteriolar vessels to the glomeruli.

Renal arterial anatomy is highly important clinically because segmental branches have limited collateral connections and because accessory renal arteries are common. Understanding these patterns is essential in renal transplantation, partial nephrectomy, vascular imaging, evaluation of renal artery stenosis, and endovascular procedures.