A fistula is an abnormal or surgically created connection between two body parts, such as an organ and a blood vessel or two vessels. While they serve different purposes—from facilitating hemodialysis to draining infection—they share a common vulnerability: the potential for blockage. Understanding the specific type of fistula is key, as the causes, symptoms, and treatments for blockage vary significantly.
Understanding How Fistulas Get Blocked
The mechanism of blockage depends entirely on the type of fistula. Blockage can result from internal issues like scar tissue or blood clots, or from the premature closure of an external opening.
Blockage in Arteriovenous (AV) Fistulas
Arteriovenous (AV) fistulas are surgically created connections between an artery and a vein, primarily used to provide reliable access for hemodialysis in patients with kidney failure. These fistulas carry a high volume of blood flow, which can sometimes lead to complications that cause a blockage. The two main causes of AV fistula blockage are:
- Stenosis (Narrowing): Due to the high pressure and increased blood flow, the blood vessel walls can thicken, and scar tissue can form. This narrows the vessel, a condition called stenosis, which restricts blood flow. This is a very common cause of AV fistula dysfunction.
- Thrombosis (Blood Clot): If blood flow slows down significantly due to stenosis or inflammation, blood clots can form inside the fistula. This thrombosis can cause a partial or complete blockage, preventing effective dialysis.
Blockage in Anal Fistulas
An anal fistula is a small tunnel connecting an infected gland inside the anus to an opening in the skin around it. The vast majority of anal fistulas are caused by a previous anal abscess. Blockage in an anal fistula typically occurs when:
- External Opening Closes Prematurely: If the external opening of the fistula heals over and closes before the underlying infection has fully resolved, pus and bacteria can become trapped inside the tract. This leads to a build-up of pressure and the re-formation of a painful abscess.
- Debris Clogs the Tract: The constant turnover of cells and presence of inflammatory tissue can cause debris to obstruct the fistula tract, contributing to infection and preventing natural drainage.
Signs and Symptoms of a Blocked Fistula
Recognizing the signs of a blocked fistula is crucial for prompt treatment. The symptoms differ depending on the fistula's location and type.
Symptoms of a blocked AV fistula (for dialysis):
- Absence of a "thrill": A healthy AV fistula has a characteristic vibration, or "thrill," which can be felt by touching the skin over it. If the thrill is absent or significantly diminished, it's a strong indicator of blockage.
- Absence of a "bruit": A stethoscope can be used to listen for a "bruit," or a whooshing sound, caused by blood flowing through the fistula. An abnormal or absent bruit suggests poor blood flow.
- High venous pressures during dialysis: The narrowing or blockage in the fistula can cause high venous pressures, which is a key sign of a problem during dialysis treatment.
- Swelling: Swelling in the arm where the fistula is located can indicate a flow issue.
Symptoms of a blocked anal fistula:
- Recurrent Abscesses: The most common sign of a blocked anal fistula is the return of a painful, swollen, pus-filled lump near the anus.
- Constant Pain: Pain in the rectal and anal area, especially when sitting or during a bowel movement, is a significant symptom.
- Fever and Chills: An infection trapped by a blocked tract can cause systemic symptoms like fever and chills.
- Inflammation: Redness and inflammation around the external opening may indicate that the tract is blocked and infection is building up internally.
Risks and Complications of Blockage
Leaving a fistula blockage untreated can lead to serious health complications, ranging from treatment failure to life-threatening infection.
- For AV fistulas, an untreated blockage means failed dialysis access, necessitating an alternative, potentially less effective method like a catheter. A blocked fistula can also increase the risk of blood clots traveling to the lungs (pulmonary embolism) or brain (stroke). Large AV fistulas put extra strain on the heart due to increased blood flow, and a blocked fistula can exacerbate this, potentially leading to heart failure.
- For anal fistulas, the risks are centered on the trapped infection. This can cause recurrent abscesses, ongoing pain, and if the infection spreads, a potentially life-threatening condition called sepsis. Chronic inflammation from a long-standing, blocked fistula can also damage the nearby sphincter muscles, leading to fecal incontinence, or, in very rare cases, anal cancer.
Comparison of Blockage Types and Treatments
| Feature | AV Fistula Blockage | Anal Fistula Blockage |
|---|---|---|
| Primary Cause | Scar tissue (stenosis) or blood clots (thrombosis) | Premature external healing trapping infection, or clogged with debris |
| Typical Symptoms | Loss of "thrill" or "bruit," high venous pressure, swelling | Recurrent painful abscesses, fever, increased pain |
| Risks of Blockage | Dialysis failure, blood clots, heart strain | Recurrent infection, sepsis, sphincter muscle damage |
| Primary Treatment Goal | Re-establish adequate blood flow for dialysis | Drain trapped infection and allow the tract to heal properly |
| Common Treatments | Angioplasty, stenting, thrombectomy | Abscess drainage, seton placement, surgery (fistulotomy) |
Treatment Options for a Blocked Fistula
Treatment for a blocked fistula depends on its type, location, and the severity of the blockage. All treatments should be performed by a qualified medical professional.
Treatment for a blocked AV fistula
- Percutaneous Transluminal Angioplasty (PTA): A minimally invasive procedure where a balloon catheter is inserted and inflated at the blockage site to widen the vessel and restore blood flow.
- Vascular Stenting: A small mesh tube called a stent may be placed to keep the vessel open after angioplasty, preventing it from collapsing.
- Thrombectomy/Thrombolysis: For blood clots, doctors can either use a mechanical device to physically break up and remove the clot (thrombectomy) or inject clot-dissolving medication directly into the clot (thrombolysis).
- Surgical Revision: In cases where less invasive methods are unsuccessful, a surgeon may operate to remove the blockage or bypass the narrowed section of the vessel.
Treatment for a blocked anal fistula
- Incision and Drainage: A blocked anal fistula usually presents as a painful abscess that requires immediate drainage. This is often an emergency procedure to relieve pressure and infection.
- Seton Placement: A surgeon may place a seton, which is a soft surgical thread or rubber band, into the fistula tract. The seton helps to keep the tract open, allowing it to drain continuously, and promotes healing from the inside out.
- Fistulotomy: For less complex fistulas, a surgeon may cut open the entire tract and allow it to heal from the bottom up.
- Other Surgical Options: For more complex fistulas, other procedures like an advancement flap or the LIFT procedure (ligation of intersphincteric fistula tract) may be used to address the internal opening while preserving sphincter muscles.
Preventing Fistula Blockage
While not all blockages are preventable, certain measures can help reduce the risk, particularly for AV fistulas. Physical examination and clinical monitoring are key to AV access maintenance.
- For AV fistula patients:
- Perform daily checks: Regularly feel for the "thrill" and listen for the "bruit" to monitor blood flow. Contact your doctor immediately if these are absent.
- Avoid constrictive pressure: Do not wear tight clothing or jewelry on the fistula arm. Avoid sleeping on the arm or carrying heavy bags with it.
- Protect the access site: Avoid taking blood pressure measurements, getting blood draws from, or allowing IV cannulas to be inserted into the fistula arm.
- For anal fistula patients:
- Ensure proper drainage: Following an anal abscess, it is important to ensure the underlying tract is properly treated to prevent the external opening from closing prematurely.
- Maintain hygiene: Keeping the area clean can prevent clogging from debris and reduce infection risk.
Conclusion
In conclusion, the answer to the question, "Can a fistula get blocked?" is a definitive yes, but the implications vary by fistula type. An AV fistula for dialysis can be blocked by clots or scar tissue, risking dialysis failure and heart problems. An anal fistula can become blocked by premature healing, trapping infection and leading to recurrent abscesses or sepsis. Vigilance, early detection of symptoms, and prompt medical treatment are essential to manage and treat a blocked fistula effectively, preventing more serious complications and ensuring the best possible health outcomes.
