Accessory Renal Artery: Causes, Symptoms, and Treatment

An accessory renal artery is an extra blood vessel that supplies one or both kidneys alongside the main renal artery. Roughly one in five people has at least one, according to a large systematic review pooling data from studies worldwide. Most never know it exists because it causes no symptoms. But when an accessory artery does cause trouble, it can show up as hard-to-control high blood pressure or a blocked urine outflow, and knowing what you’re dealing with changes the surgical playbook for everything from kidney transplants to aortic aneurysm repairs.

How Common Are Accessory Renal Arteries

Most people have a single artery feeding each kidney. A meta-analysis in Clinical Anatomy found that about 79% of people fit this textbook pattern, while the pooled prevalence of having at least one accessory renal artery sat at roughly 21%.¹ That makes them one of the most common vascular variants in the entire body. Having a single extra artery is the usual scenario, seen in about 19% of people. Having two extras drops to under 2%, and three or more is exceedingly rare.

The vast majority of these accessory vessels branch directly off the abdominal aorta, the large artery running down the center of the torso. The same meta-analysis estimated that about 88% of accessory renal arteries originate from the aorta, while roughly 8% arise as early branches off the main renal artery itself.¹ Rarer origins include the common iliac artery or the celiac trunk, but those show up in fewer than one in ten thousand cases. Where the extra artery enters the kidney also matters: some feed the upper pole, some the lower pole, and some enter at the hilum (the indent where the main vessels normally connect).

Why They Form

Accessory renal arteries are not caused by disease. They are developmental leftovers from how the kidneys take shape during embryonic life. While a fetus is growing, the kidneys start low in the pelvis and gradually migrate upward into their final position. During that journey, they pick up blood supply from a series of temporary vessels sprouting off the aorta. The standard story, taught in anatomy textbooks for over a century, held that the kidneys simply retain whichever mesonephric arteries they encounter on the way up.

More recent experimental work has challenged that classic account. A study using dye and resin injections in rat embryos found that most of those early mesonephric arteries had already broken down before the kidney even began its ascent. Instead, the definitive renal arteries appeared as new branches sprouting from the aorta and from a structure called the para-aortic ridge.² The implication is that accessory renal arteries are not so much “leftover” vessels as “extra sprouts” that formed during this phase and were never pruned back. The result is a kidney with two or more independent arterial supplies, each feeding its own segment of tissue. Because those segments do not share much cross-circulation, the territory served by each artery is essentially its own island of blood flow.

Cadaveric dissection studies continue to confirm that the specific patterns of accessory arteries are consistent with persistence of vessels from these caudal mesonephric groups, supporting the embryological explanation.³ There is no strong evidence that accessory renal arteries run in families or follow a straightforward genetic inheritance pattern. They appear to arise from normal variation in embryonic vascular development rather than from a specific gene mutation or environmental exposure.

When Accessory Renal Arteries Cause Problems

The majority of people with an accessory renal artery live their whole lives without any symptoms at all. The vessel quietly feeds its segment of kidney tissue and nobody is the wiser. Problems arise in two main situations: when the accessory artery develops narrowing (stenosis), or when it physically compresses the ureter, the tube that drains urine from the kidney to the bladder.

Renovascular Hypertension

When an accessory renal artery becomes stenotic, the segment of kidney it feeds gets less blood than it expects. That underperfused tissue responds by ramping up production of renin, a hormone that drives blood pressure higher. This is the same mechanism behind renovascular hypertension caused by narrowing of the main renal artery, but it can be sneakier because the main renal artery looks perfectly normal on standard imaging. A case report described a 39-year-old woman who arrived at the emergency department with a hypertensive crisis and brain swelling caused by the extreme blood pressure. Her main renal arteries were normal, but a CT angiogram revealed an inferior polar accessory artery with about 50% narrowing of its diameter.⁴

A separate report documented two patients whose accessory renal artery stenosis led to renin-dependent hypertension and secondary hyperaldosteronism, a condition marked by low potassium levels and elevated aldosterone that results from the excess renin.⁵ These cases illustrate why accessory renal arteries deserve consideration in younger patients with resistant hypertension, particularly when the usual workup comes back clean. Standard screening for renal artery stenosis focuses on the main arteries, which means accessory-artery stenosis can be missed entirely if the radiologist is not looking for it.

Ureteral Obstruction and Hydronephrosis

A lower-pole accessory renal artery sometimes crosses in front of the ureter right where it meets the renal pelvis, the funnel-shaped collection point for urine. That crossing can compress the ureter enough to block urine drainage, causing the kidney to swell with backed-up urine, a condition called hydronephrosis.⁶ In one study of kidneys with ureteropelvic junction obstruction, about 29% had an identifiable artery crossing at the junction on angiography.⁷ Symptoms of this kind of obstruction include flank pain, recurrent urinary tract infections, and sometimes blood in the urine. In children, the swelling may be picked up on prenatal ultrasound before any symptoms appear.

How They Are Detected

Accessory renal arteries are usually found incidentally during imaging done for another reason, such as evaluating a potential kidney donor or planning an abdominal surgery. Several imaging tools can detect them, each with different strengths.

CT angiography is the workhorse for preoperative vascular mapping. A study evaluating its accuracy in potential kidney donors found that multidetector CT angiography had about 88% sensitivity and 98% specificity for detecting accessory arteries, with overall agreement between CT findings and what surgeons actually saw at about 94%.⁸ CT is fast, widely available, and gives a detailed three-dimensional picture of the anatomy. Its main drawback is radiation exposure and the need for iodine-based contrast dye, which is a concern for patients with impaired kidney function.

MR angiography offers a radiation-free alternative. One study found it identified all main renal arteries and 13 of 17 accessory renal arteries detected by conventional angiography, though a few small accessory vessels were missed and some were too small to fully evaluate for stenosis.⁹ Another study confirmed comparable results, with MR angiography identifying the large majority of accessory arteries found on conventional digital subtraction angiography.¹⁰ MRI tends to miss the smallest accessory vessels, which is usually acceptable because the clinically significant ones are large enough to visualize.

Ultrasound is the least invasive option and the one most likely to be tried first in a screening setting. Multi-modal ultrasound combining standard gray-scale imaging with color Doppler and contrast enhancement achieved about 82% sensitivity with no false positives when compared against CT angiography in a study of 73 patients.¹¹ Ultrasound’s miss rate for small accessory arteries is higher than that of CT or MRI, but when it does identify one, the finding is highly reliable. For detecting stenosis within an accessory artery specifically, intrarenal Doppler ultrasound with sampling from the upper and lower poles of the kidney can pick up flow patterns suggestive of a narrowed supply artery, even when the artery itself is not directly visible.¹²

Treatment When Intervention Is Needed

Because most accessory renal arteries are harmless, most need no treatment. The deciding factor is whether the accessory artery is actually causing a clinical problem. When it is, the strategy depends on what kind of trouble it creates.

For hypertension driven by accessory renal artery stenosis, blood pressure medications are the first line. A literature review noted that medical therapy is standard initial management, and the same drugs used for any form of renovascular hypertension (ACE inhibitors, calcium channel blockers, and diuretics among them) are typically effective.¹³ When medications fail to bring blood pressure under control, interventional procedures become an option. These can include balloon angioplasty of the narrowed accessory artery or, in some cases, stenting. The case of the 39-year-old woman mentioned earlier was ultimately managed with a combination of amlodipine, indapamide, and perindopril, which brought her blood pressure under control within a month without the need for a procedure.⁴

For ureteral obstruction caused by a crossing vessel at the ureteropelvic junction, the traditional fix is pyeloplasty, a surgical procedure that reconstructs the junction to improve urine drainage. In recent years, a less invasive alternative called vascular hitch has gained traction, particularly in children. Instead of cutting and re-sewing the ureter, the surgeon moves the crossing vessel away from the ureter and tacks it to the kidney so it no longer compresses the outflow. One series found this laparoscopic vascular hitch procedure to be a safe alternative with a low rate of relapse, shorter hospital stays, and fewer complications compared with standard pyeloplasty.¹⁴ Another study of 35 consecutive pediatric patients confirmed low recurrence rates and emphasized that intraoperative testing after the vessel is moved can verify that the obstruction has been relieved, avoiding unnecessary reconstruction.¹⁵

Accessory Renal Arteries in Kidney Transplant Surgery

Donor kidneys with accessory renal arteries were once considered less desirable because each extra artery must be dealt with surgically. The surgeon either reconstructs the arteries (joining them into one or creating separate connections to the recipient’s blood supply) or, for very small accessory vessels, sometimes ligates (ties off) the extra artery. Both approaches add time and complexity to the operation.

The good news is that outcomes have proven reassuring. A study comparing transplants using kidneys with multiple arteries to those with a single artery found that while warm ischemia time and total surgery time were longer for multi-artery grafts, kidney function at one week and one year was comparable between groups. Graft loss and revision rates were slightly higher when the accessory artery was simply ligated rather than reconstructed, but delayed graft function and rejection rates were not increased.¹⁶ Doppler ultrasound follow-up in these patients showed that the small areas of reduced blood flow caused by ligating a minor accessory artery tended to improve over time as blood supply rerouted through surrounding tissue.

A larger analysis confirmed these findings at a center level. Although cold ischemia time was modestly longer for multi-artery grafts (about 35 minutes versus 29 minutes), there was no significant difference in delayed graft function, early graft loss, or long-term graft survival between single-artery and multi-artery kidney transplants.¹⁷ The takeaway for patients waiting for a kidney: a donor organ with an extra artery is still a perfectly viable organ. Rejecting it would shrink the donor pool for no meaningful benefit.

Covering Accessory Arteries During Aortic Aneurysm Repair

Endovascular aortic aneurysm repair uses a stent graft placed inside the aorta to seal off the ballooning section. Sometimes an accessory renal artery originates from the segment of aorta that the graft needs to cover. Blocking that artery is an unavoidable consequence of achieving a good seal for the stent. For years, surgeons debated whether this was safe.

A systematic review in Interactive CardioVascular and Thoracic Surgery pooled the available data and found that while segmental kidney infarction occurred in varying proportions of patients (ranging widely across studies), there was no associated decline in measurable kidney function. Neither creatinine levels, glomerular filtration rate, nor the need for dialysis worsened when an accessory artery was covered, even in a subgroup of patients who already had impaired kidneys before the repair.¹⁸ A separate long-term study found renal infarctions in 84% of kidneys whose accessory artery was covered, but no significant long-term decline in filtration rate compared with patients whose accessory arteries were preserved, and no difference in the need for blood pressure medications.¹⁹

Another study reached the same conclusion: the loss of kidney tissue from blocking an accessory artery usually does not produce detectable problems. Importantly, no cases of endoleak (blood leaking around the graft into the aneurysm sac) related to a covered accessory artery were reported, meaning that preemptively plugging the artery before surgery to prevent leakage was unnecessary.²⁰ The practical message: surgeons do not need to avoid covering an accessory renal artery when a good stent seal requires it, and they do not need to embolize the artery beforehand.

Accessory Arteries and Kidney Tumor Surgery

Partial nephrectomy, the surgery that removes a tumor while preserving the rest of the kidney, relies on temporarily clamping blood flow to create a dry surgical field. If a surgeon clamps only the main renal artery but does not realize an accessory artery also feeds the operative area, unexpected bleeding can result. Safety protocols for robotic partial nephrectomy stress reviewing preoperative imaging specifically for accessory vessels and for how close the tumor sits to the renal hilum.²¹

Bleeding that originates from an accessory renal artery after the operation can also be difficult to manage. During standard renal angiography (where contrast is injected into the main renal artery to look for a bleeding source), the accessory artery is not opacified because it arises separately from the aorta. If the interventional radiologist is not aware it exists, the bleeding source can be missed entirely. Three-dimensional CT or MRI reconstruction done before surgery helps flag these variants in advance so they can be tracked down if post-operative bleeding occurs.²²

Horseshoe Kidneys and Other Congenital Associations

Horseshoe kidney is a congenital condition in which the two kidneys are fused at their lower poles, forming a U shape. Because the fused kidney takes an unusual path during development and ends up sitting lower than normal, its blood supply is often atypical. Vascular anomalies are the most common congenital companions of horseshoe kidneys, and accessory renal arteries show up with striking frequency.²³ A CT-based study of 145 horseshoe-kidney patients found 44 distinct combinations of accessory arteries classified by their number and origin, illustrating just how variable the blood supply can be in these patients.²⁴ Many of those accessory arteries bypass the hilum and enter the kidney directly through the parenchyma (the functional tissue), which makes any planned surgery on a horseshoe kidney substantially more complex.

Ectopic kidneys, those that never fully migrated to their expected position, similarly tend to have unusual arterial supply drawn from wherever was convenient during development. For anyone with a known congenital kidney anomaly, detailed vascular imaging before any surgical procedure is especially important because the standard anatomical assumptions do not apply.

Terminology That Shows Up in Imaging Reports

If you receive an imaging report mentioning your renal arteries, you may encounter several overlapping terms. “Accessory renal artery” is the broadest label and generally means any extra artery to the kidney. Some older classification systems make a finer distinction: “accessory” for an extra artery arising from the aorta, and “aberrant” for one arising from somewhere else, such as the iliac artery. You may also see “hilar artery” (entering at the normal kidney entry point), “superior polar artery” (feeding the top of the kidney), or “inferior polar artery” (feeding the bottom). A “crossing vessel” in the context of ureteropelvic junction obstruction is usually a lower-pole accessory artery that runs in front of the ureter. These are all describing the same basic phenomenon from different angles: an extra arterial supply to the kidney that developed before birth and stuck around.