OVERVIEW

What is renal arteriovenous fistula?

Normally, the renal artery and renal vein run alongside each other but remain completely independent. A renal arteriovenous fistula occurs when an abnormal connection forms between the renal artery and renal vein due to various reasons (similar to one or more abnormal pipelines connecting two water pipes, with fluid flow).

Is renal arteriovenous fistula common?

This condition has a low incidence rate and is relatively uncommon. However, with advancements in imaging technology, its detection rate is gradually increasing.

Is there a gender difference in the incidence of renal arteriovenous fistula?

Congenital arteriovenous fistulas occur equally in males and females. For acquired cases, the incidence varies by gender due to different causative factors, but no significant statistical difference exists.

What are the renal artery and renal vein?

The kidneys are vital paired organs in the human body, each functioning independently. They require blood supply for oxygen and nutrient delivery while eliminating metabolic waste. The renal artery is the blood vessel that carries oxygen-rich blood from the heart to the kidneys, while the renal vein transports blood containing metabolic waste from the kidneys back to the heart.

The renal artery carries 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 lies in front of the renal artery and is more superficial.

Is the renal artery important?

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

SYMPTOMS

What are the symptoms and manifestations of renal arteriovenous fistula?

The manifestations of renal arteriovenous fistula are related to the cause, size and location of the fistula, as well as the duration of the condition. Some individuals may be asymptomatic, and even those with symptoms often exhibit nonspecific signs (i.e., the disease cannot be diagnosed based solely on symptoms). However, common symptoms include:

• Hypertension: Most frequently seen in acquired cases, often presenting as persistently elevated blood pressure after trauma or surgery, with notably high readings.
• Hematuria: Most common in congenital cases, which may present as either gross or microscopic hematuria, sometimes accompanied by blood clots.
• Flank pain and renal insufficiency: Often manifests as dull discomfort or soreness in the affected flank. Severe colic may occur if rupture, bleeding, or ureteral obstruction by blood clots develops. Reduced blood supply to the affected kidney may lead to renal insufficiency in severe cases.
• Heart failure: Increased venous return to the heart may cause symptoms such as chest tightness and shortness of breath.
• Abdominal bruit: A continuous murmur may be heard over the abdomen during auscultation.

CAUSES

What are the causes of renal arteriovenous fistula?

The common causes of renal arteriovenous fistula are divided into three types.

• Acquired: Most common, accounting for about 70%–75%, meaning it is not present at birth but develops later due to various causes (trauma, inflammation, tumors, surgery), with renal biopsy being the most frequent trigger. It often manifests as a single abnormal connecting channel.
• Congenital: Accounts for about 22%–25%, with unknown etiology, often involving multiple abnormal connecting channels.
• Idiopathic: Accounts for 3%–5%, with unknown etiology, usually involving a single abnormal connecting channel.

Among these, both congenital and idiopathic types have unclear causes. However, they are classified differently due to variations in the number of abnormal channels and associated conditions—congenital cases often lack other kidney diseases, while idiopathic cases may coexist with conditions like renal hypertension.

DIAGNOSIS

What tests are needed to diagnose renal arteriovenous fistula?

Diagnosing renal arteriovenous fistula primarily requires the following tests: color Doppler ultrasound (commonly referred to as ultrasound), abdominal CT, renal arteriography, urinalysis, and renal function tests.

Each test has its advantages and limitations, so multiple tests are often needed to confirm the diagnosis:

• Color Doppler ultrasound: Simple, convenient, non-invasive, and can be performed bedside. However, it is susceptible to intestinal gas interference, operator-dependent, and cannot provide multiple imaging slices for clinicians. It is useful for initial screening, and some experts recommend it as the first-choice method.
• Non-contrast + contrast-enhanced CT of the urinary system: CT scans include non-contrast and contrast-enhanced phases. Non-contrast CT has limited diagnostic value for this condition, while contrast-enhanced CT uses contrast agents to visualize renal arteries, veins, and ureters, identify defects, and assess blood flow. However, it involves radiation exposure and is relatively expensive.
• Renal arteriography: The gold standard for diagnosis, allowing both diagnosis and treatment. Due to its invasive nature and higher cost, it is not the first choice.
• Urinalysis: A preliminary test to detect red or white blood cells in urine, but the presence or absence of red blood cells alone cannot confirm the condition—it serves only as a reference.
• Renal function tests: A blood test to assess overall kidney function. Even individuals with only one kidney may show normal results.

While the above tests are primarily used for diagnosis, additional tests such as complete blood count, coagulation profile, and electrocardiogram may be required before treatment (e.g., surgery).

TREATMENT

Which department should be consulted for renal arteriovenous fistula?

Generally, treatment is sought in urology, vascular surgery, or interventional medicine departments.

How should renal arteriovenous fistula be treated?

The primary goals of treatment are symptom relief and kidney function preservation. The choice of treatment depends mainly on the cause and symptoms. Current treatment options include observation, interventional therapy, and surgical treatment:

• Observation: Suitable for patients with no obvious symptoms.
• Interventional therapy: Suitable for small fistulas, involving selective occlusion of the fistula using embolization materials to block blood flow. Due to its minimal invasiveness, simplicity, safety, and effectiveness, interventional procedures have replaced some open surgeries as the preferred treatment.
• Surgical treatment: Suitable for large fistulas or failed interventional therapy, including fistula ligation, partial nephrectomy, or nephrectomy.

What complications may occur in patients with renal arteriovenous fistula?

The most common complication is congenital heart disease.

DIET & LIFESTYLE

What precautions should patients with renal arteriovenous fistula take in daily life?

• Pay attention to rest, exercise, and balance work with leisure.
• Regular follow-up: After diagnosis, have regular check-ups to monitor disease progression and determine follow-up frequency and further treatment based on specific conditions.
• Dietary precautions: Avoid smoking and alcohol, maintain a light diet, and refrain from spicy foods.

PREVENTION

Can Renal Arteriovenous Fistula Be Prevented?

Acquired renal arteriovenous fistula is caused by trauma, inflammation, tumors, surgery, etc. There are no specific preventive measures for these primary conditions, but reducing trauma and unnecessary surgeries or punctures, along with postoperative follow-up, can aid in prevention and early detection.