Ultrasound Scan:
Dialysis AVF

A dialysis AVF (arteriovenous fistula) is a surgically created connection between an artery and a vein in a patient's arm or leg. It is commonly used for haemodialysis, a treatment method for individuals with kidney failure or end-stage renal disease (ESRD) to filter waste products and excess fluid from the blood. This involves placing two needles into a vein in the arm; one needle removes the blood to be cleaned and the other returns the cleaned blood back to the body. If these needles were to be inserted into a normal vein, this process would take an unreasonable amount of time as venous blood flow is very slow. In order to speed up this process, a surgical procedure is done to connect a vein to an artery; this is called a fistula. This fistula causes a large volume of blood flow to move through the vein and dramatically speeds up the dialysis process.

 

During the creation of a dialysis AVF, an artery is connected to a nearby vein, typically in the forearm or upper arm. This connection causes arterial blood, which carries oxygen and nutrients, to flow directly into the vein. Over time, the increased blood flow enlarges and strengthens the vein, making it suitable for repeated needle insertions for hemodialysis. The dialysis AVF is an important access site for hemodialysis because it provides a high flow rate of blood, allowing efficient removal of waste products during dialysis sessions. It is preferred over other access methods, such as dialysis catheters or grafts, due to its lower risk of infection and longer lifespan. Regular monitoring of the dialysis AVF is necessary to ensure its functionality and detect any complications. This includes regular physical examinations, checking blood flow through the access site, and periodic ultrasound assessments.

This scan usually takes 20 minutes to complete.

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A Dialysis AVF Doppler study involves assessing the fistula created for dialysis purposes. This ultrasound requires direct contact with your skin. We will require you to remove any jackets and jumper and shirt. We will provide a disposable gown for you.

We will ask you to lie on your back on our examination bed. During the scan we will apply gel to your arm and use the ultrasound machine to look at the the arteries and veins of your fistula. You will hear noises from the ultrasound machine; this is all normal and is the sound of the blood flow moving through your fistula.

A Dialysis AVF ultrasound looks at the function of the fistula and ensures there is a good amount of blood flow moving through the circuit. This scan is predominately looking for any kind of blood flow restriction/s throughout the AVF circuit; this may be in the form of a narrowing, complete occlusion or something pressing on an artery. This scan is often requested if you have have a newly created AVF, high venous pressures during dialysis, difficulty needling or the needle pulling out clots. Other reasons may include:

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Fistula creation assessment

Before a dialysis AVF is used for haemodialysis, an ultrasound can be done to evaluate the newly created fistula. The ultrasound allows the healthcare provider to assess the anatomy, blood flow, and maturation of the AVF. It helps determine if the fistula is suitable for use and if it has developed enough to provide adequate blood flow for hemodialysis.

 

Monitoring AVF functionality

Regular ultrasound examinations are performed to monitor the ongoing functionality of the dialysis AVF. These assessments typically occur during routine follow-up visits with the healthcare provider or as needed. The ultrasound provides real-time images and measurements to evaluate the blood flow within the AVF, detect any abnormalities or blockages, and assess the overall health of the access site.

 

Diagnosis of complications

Ultrasound is a valuable tool for identifying complications related to a dialysis AVF. It can help diagnose issues such as stenosis (narrowing) or thrombosis (blood clot) within the AVF, aneurysm (abnormal dilation), pseudoaneurysm (localised swelling), or steal syndrome (improper blood flow to the hand or arm). Early detection of these complications allows for timely intervention and management.

 

Preoperative planning

In cases where intervention or surgical procedures are required to address complications or optimise the dialysis AVF, ultrasound can aid in preoperative planning. It helps the healthcare provider visualise the anatomy, pinpoint the location and severity of any stenosis or blockages, and determine the most appropriate intervention strategy.

 

Overall, ultrasound imaging of a dialysis AVF provides valuable information about its functionality, maturation, and potential complications. It helps guide clinical decision-making, optimize dialysis treatment, and ensure the long-term viability of the access site.

Dialysis AVF (arteriovenous fistula) issues can lead to various symptoms and complications. Issues may include the dialysis needle pulling out clots, difficult to needle​​, high venous pressure on the dialysis machine, unusual persistent bleeding after removing the dialysis needles. Additional issue may include:

 

Decreased or absent thrill or bruit

A thrill is a vibrating sensation and a bruit is a whooshing sound that can be felt or heard over a healthy AVF. If there is a decrease or absence of these sensations, it may indicate a problem such as a clot, stenosis (narrowing), or blockage in the AVF.

 

Swelling or bulging

Swelling or bulging along the path of the AVF can occur due to an aneurysm (abnormal dilation) or pseudoaneurysm (localised swelling) formation. These can be tender to touch and may cause discomfort.

 

Pain or discomfort

Patients may experience pain or discomfort at the AVF site or along the path of the AVF. This can be due to complications such as stenosis, thrombosis (blood clot), infection, or aneurysm.

 

Poor blood flow during dialysis

If there are issues with the AVF, the blood flow during dialysis may be compromised. Signs of poor blood flow include decreased dialysis efficiency, prolonged bleeding after needle removal, or inadequate clearance of waste products during dialysis.

 

Hand or arm numbness or weakness

In some cases, AVF-related issues can lead to decreased blood flow to the hand or arm, resulting in symptoms such as numbness, tingling, or weakness.

 

Skin changes

Skin discolouration, ulcers, or open wounds in the hand or arm may indicate compromised blood flow and poor healing at the AVF site.

The treatment of dialysis AVF (arteriovenous fistula) issues depends on the specific problem identified. Here are some common treatments for different AVF issues:

 

Stenosis or blockage: If there is a narrowing or blockage in the AVF, treatments may include:

• Angioplasty: A minimally invasive procedure where a small balloon is inflated to widen the narrowed or blocked area, restoring blood flow.

• Stent placement: In some cases, a stent (a small mesh tube) may be inserted to help keep the AVF open and maintain adequate blood flow.

 

Thrombosis (blood clot): If a blood clot is causing the issue, treatments may involve:

• Thrombectomy: A procedure to remove the blood clot from the AVF.

• Thrombolysis: The use of medications to dissolve the blood clot and restore blood flow.

 

Aneurysm or pseudoaneurysm: If an aneurysm or pseudoaneurysm is present, treatment options may include:

• Surgical repair: The aneurysm or pseudoaneurysm may be surgically repaired to prevent rupture and restore normal blood flow.

• Endovascular techniques: Minimally invasive procedures, such as coil embolization or stent graft placement, may be used to treat the aneurysm or pseudoaneurysm.

 

Infection: If an infection is present at the AVF site, treatment may include:

• Antibiotics: Depending on the severity and type of infection, antibiotics may be prescribed to eliminate the infection.

• Surgical intervention: In some cases, surgical drainage or debridement may be necessary to treat the infection.

 

Poor blood flow or inadequate dialysis: If the AVF is not providing adequate blood flow or dialysis efficiency, treatment options may include:

• Revision surgery: Surgical correction or adjustment of the AVF to improve blood flow and dialysis outcomes.

• Creation of a new access site: In some cases, if the issues with the AVF are persistent and cannot be effectively addressed, a new AVF may need to be created.