A fistulogram is a diagnostic imaging test that allows physicians to visualize the inside of an abnormal connection or surgically created passageway, known as a fistula or graft. This procedure uses X-ray technology, specifically fluoroscopy, in conjunction with a contrast agent, often referred to as a dye. The contrast agent is opaque to X-rays, making the internal structure visible on a monitor as it flows through the vessel. By capturing these real-time images, doctors can accurately map the entire passageway and identify any internal structural issues.
Why the Study Is Necessary
Fistulograms are performed to monitor and maintain the function of vascular access sites in patients undergoing hemodialysis. These access sites, which include arteriovenous (AV) fistulas or AV grafts, are surgically created connections between an artery and a vein. These connections allow for the high blood flow rates required for effective dialysis treatment, but the constant, high-pressure flow can cause damage or changes to the vessel walls over time.
The purpose of the fistulogram is to diagnose specific problems that compromise the effectiveness of dialysis and lead to access failure. Narrowing of the blood vessel, known as stenosis, is a common issue that reduces blood flow and triggers machine alarms. The test also detects complete blockages caused by blood clots (thrombosis), as well as abnormal ballooning of the vessel wall (aneurysm formation). Addressing these issues promptly helps to extend the functional lifespan of the patient’s vascular access.
What to Expect Before the Study
Preparation for a fistulogram begins with a review of the patient’s medical history and current medications. Patients are instructed to fast, meaning they should not eat any solid food for at least six to eight hours prior to the procedure. Clear liquids, such as water or juice, are often permitted up to two hours before the test time.
Patients must disclose all medications, especially blood thinners like warfarin, and certain diabetes medications such as metformin. Physicians may need to adjust or temporarily stop the dosage of these drugs to mitigate the risk of bleeding or potential interactions with the contrast agent. Disclosure of any allergies, particularly to iodine or contrast dye, is mandatory so that the medical team can take necessary precautions. Finally, the patient must sign an informed consent form after the procedure has been fully explained.
How the Imaging Procedure Is Performed
The fistulogram procedure is performed by an interventional radiologist and usually takes between 30 and 60 minutes. The patient is positioned on an X-ray table, and the vascular access site, usually in the arm, is thoroughly cleaned with an antiseptic solution. A local anesthetic is injected into the skin around the access site to numb the area and ensure comfort during the procedure.
Once the area is numb, the physician inserts a specialized needle or a thin, flexible tube called a catheter directly into the fistula or graft. Fluoroscopy is used to precisely position the catheter within the blood vessel. The contrast dye is then injected through the catheter, and X-ray images immediately capture the flow through the vessel.
The radiologist watches the dye flow on a video monitor, which reveals the internal structure of the fistula or graft and highlights any areas where the flow is restricted. If significant narrowing (stenosis) is identified, the physician can perform an immediate therapeutic intervention. This may involve angioplasty, where a small balloon-tipped catheter is advanced to the narrowed site and inflated to stretch the vessel open, restoring proper blood flow. In some cases, a small metal mesh tube, known as a stent, may be placed to keep the newly opened segment from collapsing.
After the Study: Recovery and Safety
Following the imaging and any necessary intervention, the access needle or catheter is removed, and pressure is immediately applied to the puncture site to control bleeding. Patients are then moved to a recovery area where they are monitored for a period, typically ranging from 30 minutes to two hours, to ensure the access site is stable.
During the injection of the contrast dye, some patients experience a temporary feeling of warmth or flushing throughout the body. A brief metallic taste in the mouth is also a common side effect of the contrast agent. Patients are advised to drink plenty of fluids after the procedure to help their body flush the contrast material out of their system.
Patients should monitor the access site at home for any signs of complications. Bruising and mild soreness at the puncture site are normal, but excessive swelling, severe pain, or any drainage should be reported to the care team. Patients are instructed to avoid strenuous activities and heavy lifting with the access arm for at least 24 hours to allow the puncture site to heal fully.