The human body supplies blood to each kidney through a single renal artery that branches off the aorta. An accessory renal artery is a common anatomical variation where an additional artery also provides blood to a kidney. This variation is not a disease but a difference present from birth. Since it often causes no issues, most individuals are unaware of its existence. The presence of one or more of these extra arteries simply means the kidney’s blood supply is segmented among multiple vessels.
Formation and Prevalence
The development of accessory renal arteries is rooted in the embryological journey of the kidneys. During fetal development, the kidneys begin their formation low in the pelvis and ascend to their final position in the upper abdomen. During this migration, they receive their blood supply from a series of temporary arteries that sprout from the aorta.
As the kidneys reach their destination, a single, main renal artery takes over, and the transient, lower vessels regress and disappear. An accessory renal artery is the result of one of these embryonic arteries persisting instead of regressing. These vessels are considered remnants of the fetal circulatory system.
This anatomical variation is quite common, with studies showing it is present in approximately 30% of the population. While most individuals have a single renal artery for each kidney, finding one or more additional arteries is a frequent variant of human anatomy.
Potential Clinical Significance
Although an accessory renal artery is harmless in most cases, its presence can sometimes have clinical implications. One noted association is with renovascular hypertension, a form of high blood pressure caused by reduced blood flow to the kidneys. If an accessory artery is narrow (stenosis), it can limit blood supply to the portion of the kidney it feeds. This reduction in flow signals the kidney to release hormones that constrict blood vessels and raise overall blood pressure.
Another potential issue involves the ureter, the tube that carries urine from the kidney to the bladder. An accessory artery may cross over and compress the ureter at the ureteropelvic junction (UPJ). This can lead to a blockage called UPJ obstruction, causing urine to back up and the kidney to swell (hydronephrosis), which can result in flank pain or infections.
The existence of these arteries is also an important consideration for surgeons. Before procedures such as kidney donation or removal, knowledge of all renal blood vessels is needed. Pre-operative imaging allows surgeons to identify any accessory arteries and plan the surgery accordingly to prevent damage that could compromise blood flow.
Diagnosis and Management
Most accessory renal arteries are asymptomatic and are discovered incidentally during imaging studies like computed tomography (CT) scans, magnetic resonance imaging (MRI), or ultrasounds performed for unrelated medical reasons. Their discovery often has no bearing on the patient’s health. A physician might note the variation in the medical report, but no further action is needed if it is not causing complications.
When an accessory renal artery is not causing symptoms, no treatment is required. Management is only considered if the artery is directly linked to a medical problem, such as hypertension or a ureteral obstruction. For renovascular hypertension, the initial approach is medication to control blood pressure, such as ACE inhibitors.
If medication is not effective or if there is significant stenosis, a procedure like angioplasty, with or without stenting, may be performed to widen the narrow artery. In cases of UPJ obstruction caused by a crossing artery, a surgical procedure called pyeloplasty is performed. This surgery involves repositioning the ureter to relieve the compression and ensure urine can flow freely from the kidney.