Renal Artery Aneurysm
A renal artery aneurysm is an abnormal enlargement (ballooning) of a portion of the renal artery, the blood vessel that carries blood from the aorta to the kidney. Renal artery aneurysms are uncommon but well recognized and are increasingly identified as an incidental finding on imaging performed for other reasons. Most are small and cause no symptoms. Larger aneurysms, aneurysms with certain characteristics, or aneurysms in specific patient groups (such as women of childbearing age who may become pregnant) may require closer evaluation or treatment. Rupture is uncommon overall but is a serious complication when it occurs. Evaluation typically involves imaging (particularly CT or MR angiography) and, in selected cases, catheter angiography and consideration of treatment options.
What is it?
The renal arteries arise from the aorta and carry oxygen-rich blood to the kidneys. Within the kidney, the main renal artery branches into progressively smaller vessels that supply distinct segments of the kidney. A renal artery aneurysm is an abnormal enlargement or ballooning of a portion of the renal artery. The affected segment is dilated to a size significantly larger than the normal artery, typically defined as a diameter greater than about 1.5 to 2 times the normal artery diameter or exceeding a specific absolute size threshold.
Renal artery aneurysms can be classified in several ways.
By location, they can involve the main renal artery, branch arteries within the renal hilum (where the arteries enter the kidney), or intrarenal segments (within the kidney tissue itself). Aneurysms at branch points (where the artery divides) are particularly common. Intrarenal aneurysms are often small and identified with detailed imaging or catheter angiography.
By shape, aneurysms can be saccular (a focal outpouching or “sac” from the side of the artery) or fusiform (a longer, more spindle-shaped dilation of a segment of artery). Saccular aneurysms are the most common type and are what most people picture as an aneurysm.
A pseudoaneurysm (or “false aneurysm”) is a related but distinct entity in which the aneurysm wall is not composed of all the layers of a normal artery. Pseudoaneurysms typically develop as a result of vessel injury (from trauma, prior surgery or biopsy, or infection) and behave somewhat differently from true aneurysms in terms of natural history and treatment planning.
Several conditions predispose to renal artery aneurysm formation.
Fibromuscular dysplasia (FMD) is a non-atherosclerotic condition affecting the walls of medium-sized arteries and is one of the most important causes of renal artery aneurysms, particularly in younger and middle-aged women. FMD often produces characteristic “string of beads” appearance on imaging with alternating areas of narrowing and dilation.
Atherosclerosis (the buildup of plaque in artery walls) is another important cause, particularly in older adults and in patients with cardiovascular risk factors.
Connective tissue disorders—such as Ehlers-Danlos syndrome (particularly the vascular type), Marfan syndrome, and Loeys-Dietz syndrome—can predispose to aneurysms throughout the vascular system, including the renal arteries.
Certain autoimmune conditions, particularly polyarteritis nodosa (a vasculitis affecting medium-sized arteries), can cause renal artery aneurysms as part of the broader disease.
Trauma, prior arterial procedures, and infections (mycotic aneurysms, which result from infection of the vessel wall) can also cause aneurysms or pseudoaneurysms.
Pregnancy and childbirth are associated with an increased risk of renal artery aneurysm rupture, particularly during the third trimester and around delivery, likely due to hormonal effects on artery walls and increased blood flow. This is an important consideration in the management of women of childbearing age.
The majority of renal artery aneurysms are small (typically less than 2 cm) and cause no symptoms. Many are identified incidentally on imaging performed for other reasons—such as evaluation of abdominal pain, kidney stones, or unrelated conditions. When symptoms occur, they may include flank or back pain, high blood pressure (which can be caused or worsened by the aneurysm through effects on renal blood flow), blood in the urine, and, less commonly, symptoms specific to complications.
Complications of renal artery aneurysms include rupture, dissection (a tear within the wall of the aneurysm or nearby artery), thrombosis (clotting within the aneurysm), and embolism (clots or debris breaking off from the aneurysm and traveling to smaller kidney vessels, potentially causing renal infarction). Rupture is the most serious complication and typically presents with sudden severe abdominal or flank pain, low blood pressure, or, in severe cases, shock. Rupture is uncommon overall but is a serious event, and pregnancy-related rupture has particularly high mortality rates for both mother and fetus, though it remains a rare event.
Diagnosis is based on imaging. CT angiography is one of the primary imaging tests and provides detailed information about the aneurysm’s location, size, shape, wall characteristics, and relationship to nearby structures. MR angiography provides similar information without ionizing radiation and can be useful in specific circumstances (such as young patients, pregnant patients, or patients with contrast contraindications). Ultrasound (including Doppler evaluation) may identify some aneurysms but is less sensitive and less detailed than cross-sectional imaging. Catheter angiography provides the most detailed evaluation, particularly for small or intrarenal aneurysms, and is often used when treatment is being planned.
When a renal artery aneurysm is identified, evaluation typically includes assessment of the entire vascular system (particularly for fibromuscular dysplasia, which often affects multiple arterial beds), blood pressure measurement, blood tests including kidney function, and, in selected patients, evaluation for underlying connective tissue disorders or vasculitis.
For patients with suspected FMD, evaluation for aneurysms and other vascular findings elsewhere is important (FMD commonly affects the carotid arteries, and evaluation for cerebral aneurysms is often considered). For patients with suspected connective tissue disorders, genetic counseling and testing may be appropriate.
Important to Know
Management of a renal artery aneurysm is highly individualized based on the aneurysm’s size, location, shape, associated features, patient factors (including pregnancy potential), the underlying cause, and available expertise. Care is best coordinated by multidisciplinary teams that may include vascular specialists (interventional radiologists, interventional vascular surgeons, or vascular medicine specialists), nephrologists, and, when relevant, geneticists, rheumatologists, obstetricians, and other specialists.
For small, asymptomatic saccular renal artery aneurysms with typical features and no concerning findings, observation with periodic imaging is often appropriate. Follow-up imaging (typically CT or MR angiography) is generally recommended at intervals such as annually or every few years initially, with the interval adjusted based on stability and clinical context. This approach reflects the generally low risk of rupture in small stable aneurysms.
Treatment (rather than observation) is generally recommended in several situations. Traditional size-based thresholds have suggested treatment for aneurysms greater than 2 cm in most patients, though evidence-based guidelines and thresholds continue to evolve, and decisions are increasingly individualized. Treatment is generally recommended for aneurysms with concerning features such as growth over time, dissection, associated symptoms, or rupture-related findings. Treatment is also strongly considered for aneurysms in women of childbearing age who may become pregnant, because of the increased risk of rupture during pregnancy and delivery.
Endovascular treatment has become the preferred approach for many renal artery aneurysms. Options include coil embolization (placing small coils into the aneurysm to promote clotting and exclude it from blood flow), covered stent placement (deploying a stent lined with fabric that seals off the aneurysm while preserving blood flow through the artery), and other techniques (such as flow-diverting stents in specific cases). These procedures are typically performed by interventional radiologists or interventional vascular specialists through a small puncture in the groin, with recovery times generally much shorter than open surgery.
Surgical treatment (typically involving repair, bypass, reconstruction, or, in specific cases, partial nephrectomy) is used when endovascular treatment is not suitable or has failed. Options include aneurysm resection with primary repair, patch repair, bypass grafting, or, less commonly, autotransplantation (removing the kidney, repairing the vessels outside the body, and re-implanting the kidney in a different location). Surgical approaches have become less common with the growth of endovascular options but remain important in selected cases.
For patients with fibromuscular dysplasia, comprehensive care includes evaluation of multiple arterial beds (including the carotid and vertebral arteries in the neck and brain, which are commonly affected), blood pressure management, and coordination with vascular medicine specialists. Renal artery stenosis caused by FMD may be treated with percutaneous transluminal angioplasty (typically without stenting) in appropriate patients.
For patients with connective tissue disorders, care coordination with genetics and vascular specialists is important, and management may need to consider risk of aneurysms elsewhere in the vascular system.
For patients with vasculitis (such as polyarteritis nodosa), treatment of the underlying condition (typically with immunosuppressive medications) is essential, and coordination with rheumatology is important.
For patients with pseudoaneurysms (often from trauma, prior procedures, or infection), treatment is often more urgent because pseudoaneurysms tend to have a higher risk of rupture than true aneurysms. Treatment options include endovascular procedures and, in specific cases, surgical repair or, for infected pseudoaneurysms, removal along with treatment of the infection.
Management of blood pressure is important both in aneurysm patients generally and particularly in those with associated renal artery stenosis (from FMD or other causes). ACE inhibitors or ARBs are commonly used, though care is needed in patients with certain patterns of renal artery disease. Careful monitoring is important, and coordination with nephrology or vascular medicine is often beneficial.
For women of childbearing age with known renal artery aneurysms, preconception counseling and, in many cases, treatment before pregnancy are important because of the risk of rupture during pregnancy. Coordination with obstetrics and vascular specialists is essential for women who have been treated or who have aneurysms that are not treated.
For patients with an incidentally identified renal artery aneurysm, evaluation for underlying causes may be appropriate, particularly in younger patients or those with concerning features. This may include imaging of other arterial beds, family history assessment, and, in selected cases, genetic testing.
Care is typically coordinated by vascular specialists and, when needed, nephrologists, obstetricians, geneticists, and other specialists. Imaging and laboratory findings are interpreted alongside the patient’s symptoms, examination, family history, and broader clinical context rather than in isolation.
Patient education plays an important role. Understanding the diagnosis, the meaning of the specific findings, the rationale for recommended monitoring or treatment, the importance of follow-up, the significance of any underlying conditions when identified, and warning signs of complications all contribute to appropriate care.
Red flag symptoms include sudden severe abdominal or flank pain, sudden severe back pain, low blood pressure or signs of shock (rapid heart rate, dizziness, fainting, cool clammy skin, confusion), difficulty breathing, sudden severe headache with neurological symptoms (particularly in patients with FMD, given the association with cerebral aneurysms), significant blood in the urine, sudden neurological symptoms, or rapid clinical deterioration. These warrant immediate emergency evaluation, as they may indicate rupture, dissection, or other life-threatening complications.