Renal artery embolization (RAE) is a specialized, minimally invasive treatment performed by interventional radiologists to intentionally block blood flow to a specific part of the kidney. This catheter-based procedure uses image guidance to navigate the arterial network, allowing for the highly targeted delivery of therapeutic materials. By cutting off the blood supply, the targeted tissue is starved of oxygen and nutrients, causing it to shrink or die. RAE avoids the need for a large surgical incision and is often used when traditional surgery is not the preferred choice.
Primary Medical Applications
RAE is commonly used to manage and treat kidney tumors. For patients with renal cell carcinoma (RCC), it is frequently used pre-operatively to reduce the tumor’s size and blood supply, decreasing the risk of significant blood loss during nephrectomy. RAE also serves as a palliative measure for individuals with advanced, unresectable RCC or for those too frail for major surgery, alleviating severe symptoms such as persistent flank pain or gross hematuria.
Embolization is the standard treatment for large or bleeding angiomyolipomas (AMLs), which are benign kidney tumors. AMLs over four centimeters have an increased risk of rupture and life-threatening hemorrhage.
The procedure is also an effective method for controlling acute renal hemorrhage resulting from trauma or complications following a kidney biopsy or partial nephrectomy. The goal is to stop internal bleeding caused by damaged vessels (e.g., pseudoaneurysms or arteriovenous fistulas) by selectively targeting only the abnormal vessels to preserve healthy kidney tissue.
How the Procedure is Performed
The RAE procedure begins with the patient lying on an X-ray table, typically under conscious sedation and local anesthesia applied to the access site. The radiologist gains entry into the arterial system through a small puncture in the femoral artery in the groin. A catheter is carefully guided using fluoroscopy, allowing the physician to track its movement.
Once the catheter reaches the aorta near the kidney, an iodinated contrast dye is injected. This illuminates the renal arteries, providing a precise vascular map (angiography) that identifies the specific blood vessels feeding the target area. A smaller microcatheter is then navigated into the renal artery branches until it is positioned directly within the vessel supplying the target lesion.
The next step involves delivering embolic agents, the materials used to create the blockage. These materials vary depending on the target vessel size and goal:
- Tiny particles like microspheres or polyvinyl alcohol (PVA)
- Liquid agents
- Metal coils
These agents are injected to permanently occlude the blood vessel. A final angiogram confirms that the blood flow has been successfully halted. The catheters are then removed, and pressure is applied to the access site to prevent bleeding.
Post-Procedure Care and Expectations
Following RAE, patients are moved to a recovery area for close monitoring of vital signs and the puncture site. Most patients remain for at least an overnight stay to manage anticipated side effects. The most common consequence is a temporary condition known as Post-Embolization Syndrome (PES).
PES is a cluster of symptoms resulting from the body’s inflammatory response to the sudden death of the embolized tissue. Symptoms typically include:
- Mild to moderate fever
- Nausea and vomiting
- Localized pain in the flank or abdomen
These symptoms usually begin within the first 72 hours and are self-limiting, resolving within a few days, though they can occasionally last up to ten days.
Treatment for PES is supportive, focusing on managing discomfort until the body adjusts. This involves administering pain medication, anti-nausea drugs, and fever reducers as needed, along with ensuring adequate hydration. Patients are advised to rest and avoid strenuous activity after discharge.
Potential Complications and Monitoring
RAE carries risks distinct from Post-Embolization Syndrome. One risk is non-target embolization, where embolic material inadvertently travels to an unintended artery, potentially blocking blood flow to other organs. This can lead to complications such as damage to the lower extremities or, rarely, the bowel.
Another risk is the worsening of kidney function, particularly in patients with pre-existing renal impairment. The procedure can also cause contrast-induced nephropathy, a temporary decline in kidney function due to the contrast dye. Rare adverse events include infection (renal abscess) or complications at the catheter insertion site (hematoma or pseudoaneurysm).
Long-term follow-up is necessary to ensure the success of the embolization and check for delayed complications. Monitoring includes periodic blood work to assess kidney function (creatinine and BUN levels). Imaging (CT scans or Duplex ultrasounds) is routinely performed to confirm the targeted area remains devascularized and monitor kidney health.