OVERVIEW

What are the renal artery and renal vein?

The kidneys are vital organs in the human body, with one on each side, functioning independently. They require blood supply for oxygen and nutrients while also excreting metabolic waste. The blood vessels that carry oxygen-rich blood from the heart to the kidneys are called the renal arteries, while the vessels that transport blood (now rich in waste products) back to the heart are called the renal veins.

The renal artery contains oxygen-rich blood, whereas the renal vein carries blood rich in carbon dioxide. The renal artery has thicker walls, a smaller diameter, and greater elasticity compared to the renal vein. Generally, the renal vein is located in front of the renal artery and is more superficial.

Is the renal artery important?

Although the kidneys are relatively small, accounting for only about 0.5% of total body weight, the blood flow supplied to them via the renal arteries represents 20–25% of the heart's total output. Thus, the renal artery is crucial, and severe traumatic rupture can be life-threatening.

What is a renal artery aneurysm?

A normal renal artery resembles a water pipe with uniform diameter, whereas a renal artery aneurysm occurs when the artery or its branches develop localized, permanent dilation—like one or more bulging "bubbles" on a pipe, which may vary in shape.

Are renal artery aneurysms common? Are they benign or malignant?

This condition is rare and not very common. However, with advancements in imaging technology, detection rates are gradually increasing. It is a benign condition.

Are there gender or side differences in the incidence of renal artery aneurysms?

The incidence of renal artery aneurysms shows no significant difference between the left and right sides, with bilateral occurrences accounting for about 20%. However, they are slightly more common in women than in men, and aneurysms are more prone to rupture in women of childbearing age.

SYMPTOMS

What are the types of renal artery aneurysms?

According to the Poutasse classification, renal artery aneurysms are mainly divided into four types:

• Saccular aneurysms: The most common, accounting for about 75%, primarily involving the main renal artery and its branches.
• Fusiform aneurysms: Often associated with stenosis of the main renal artery.
• Dissecting aneurysms.
• Intrarenal aneurysms: Accounting for about 17%, affecting intrarenal arteries with varied morphology.

What are the symptoms and manifestations of renal artery aneurysms?

Most renal artery aneurysms are small and asymptomatic. Even when symptoms occur, they are nonspecific (i.e., the disease cannot be diagnosed based on symptoms alone). Common symptoms include:

• Hypertension: The most common symptom. The relationship between the two is debated, but most patients return to normal blood pressure after surgery, suggesting hypertension may be related to renal artery compression or stenosis caused by the aneurysm.
• Hematuria: The severity depends on the amount of bleeding, ranging from gross hematuria to microscopic hematuria. It may result from aneurysm erosion or perforation into the collecting system (e.g., renal calyces or pelvis), causing blood to pass into the urine.
• Flank pain: Often presents as dull discomfort on the affected side. Severe colic may occur if rupture, hemorrhage, or ureteral obstruction by blood clots occurs.
• Abdominal bruit or pulsatile mass: Larger aneurysms may present as one or more pulsating lumps in the abdomen. Thin individuals with less abdominal fat may feel a pulsating cord-like structure, which is usually the normal pulsation of the abdominal aorta.

Is renal artery aneurysm serious? What complications may occur?

• Peripheral vascular intimal dissection: May indicate aneurysms in other blood vessels.
• Mural thrombus formation within the aneurysm or renal infarction due to arterial thrombosis.
• Obstructive uropathy: Compression of the renal pelvis or ureter.
• Arteriovenous fistula formation due to venous invasion.
• Spontaneous rupture and hemorrhage.

CAUSES

What are the causes of renal artery aneurysms?

• Structural damage to the arterial wall: Most commonly caused by atherosclerosis, but may also result from congenital fibromuscular dysplasia.
• Trauma: Abdominal or lumbar injuries, iatrogenic damage from procedures like biopsy or catheterization.
• Others: Conditions such as syphilis infection or bacterial arteritis.

What high-risk factors are often associated with ruptured renal artery aneurysms?

Although spontaneous rupture of renal artery aneurysms is rare, the mortality rate can reach up to 70% once rupture occurs. Therefore, special attention is required for diagnosed cases combined with the following conditions:

• Large aneurysm size (diameter exceeding 2 cm).
• Absent or incomplete calcification of the aneurysm wall.
• Hypertension, especially poorly controlled cases.
• Pregnancy.

DIAGNOSIS

What tests are needed to diagnose renal artery aneurysm?

The main tests include color Doppler ultrasound (commonly referred to as ultrasound), abdominal CT, MRI, renal arteriography, intravenous urography, urinalysis, and renal function tests.

Why are these tests performed for diagnosing renal artery aneurysm? What are their purposes?

Each test has its own advantages and limitations, so multiple examinations are often required to confirm the diagnosis:

• Color Doppler Ultrasound: Simple, convenient, and non-invasive, but results can be affected by intestinal gas and operator experience. It is useful for initial screening and observing blood flow changes but cannot definitively diagnose the condition.
• Urinary CT: CT scans include non-contrast and contrast-enhanced scans. For larger aneurysms, non-contrast CT may only show soft tissue shadows, making it difficult to distinguish from cysts or tumors. Contrast-enhanced CT uses contrast agents to visualize the renal artery, renal vein, and ureter morphology, revealing typical signs of an aneurysm.
• MRI (Non-contrast + Contrast-enhanced): This test is radiation-free but expensive, time-consuming, and unsuitable for individuals with magnetic implants or claustrophobia. Pregnant women should also avoid it. In theory, MRI can easily diagnose renal artery aneurysms.
• Renal Arteriography: The gold standard for diagnosis, but due to its invasive nature, it is not the first choice.
• Urinalysis: A preliminary test to check for red or white blood cells in urine, but the presence or absence of red blood cells alone cannot confirm a renal artery aneurysm—it serves only as a reference.
• Renal Function Tests: A blood test that assesses overall kidney function. Even individuals with only one kidney may show normal results. This test helps guide treatment decisions.

Of course, the above tests are primarily used for diagnosis. Before surgical or other treatments, additional tests such as complete blood count, coagulation tests, and electrocardiograms are often required to assess surgical feasibility.

TREATMENT

Which department should I visit for renal artery aneurysm?

Generally, you can choose urology, vascular surgery, or interventional radiology for treatment.

How should renal artery aneurysm be treated?

The main treatment options for this condition are conservative management and surgical intervention:

• Conservative treatment: Suitable for small aneurysms (less than 2 cm in diameter) with fully calcified walls, normal blood pressure, and no symptoms. However, regular monitoring of aneurysm progression is required, with follow-up intervals determined by the condition.
• Surgical treatment:
  • The primary goals of surgery are to prevent spontaneous rupture of the renal artery or control hypertension potentially caused by the aneurysm. Therefore, surgery is mainly recommended for patients with high-risk factors for spontaneous rupture (as mentioned above).
  • With advancements in medicine, the main surgical options now include interventional therapy and open surgery. Due to its minimal invasiveness, simplicity, safety, and effectiveness, interventional therapy has replaced some open surgeries and become the preferred treatment method.

How should pregnant patients with renal artery aneurysm be managed?

During pregnancy, renal artery aneurysms become a high-risk factor for spontaneous rupture due to hormonal changes and other physiological factors, leading to higher mortality rates. Additionally, certain diagnostic procedures may pose risks of fetal malformations, and there is no clearly defined optimal surgical approach. Therefore, it is recommended that patients with larger renal artery aneurysms undergo surgery before pregnancy.

DIET & LIFESTYLE

What precautions should patients with renal artery aneurysms take in daily life?

• Symptom control: Such as medication for blood pressure management;
• Regular follow-ups: Schedule periodic check-ups after diagnosis to monitor disease progression, with frequency determined by individual conditions;
• Dietary care: Avoid smoking and alcohol, maintain a light diet, and refrain from spicy foods.

PREVENTION

Can renal artery aneurysms be prevented?

To address the causes of this condition, reducing structural damage to arterial walls—such as avoiding trauma to the lumbar and abdominal areas and minimizing iatrogenic injuries like puncture biopsies and catheter insertions—can help. Additionally, maintaining healthy lifestyle habits and preventing infections like syphilis may contribute to reducing the occurrence of renal artery aneurysms.