Dialysis is a procedure that is required in patients with kidney failure for purification of toxins from blood which was originally the function of kidneys. The longest-lasting and best type of dialysis access is by an arteriovenous fistula, or AV fistula which is created after surgery in left upper limb preferably. In this, a vein and an artery are joined together to facilitate the drawing of blood by the machine and its transfer back into the body during dialysis. The surgery is usually done under local or regional anaesthesia.

Arteriovenous fistulae also lead to few complications like-

• Failure of AV fistula-

  Success of the surgery for AV fistula largely depends on the condition of the artery and the recipient veins in the arms and forearms region. Usually, the patients who come for AV fistula surgery have had multiple pricks in the veins of the forearm because of the need for iv access for antibiotics and blood transfusion. In such cases, walls of the veins are damaged and the quality of AV Fistula formed is not viable sometimes due to which another attempt of surgery might be required in future for fistula formation at some other site.

• Infection-

  Infections like cellulitis can develop around the fistula, which manifests as localized redness and swelling and is usually easily treated with antibiotics. But serious infections are associated with aneurysmal dilation of blood vessels, blood collection or abscesses, which requires surgical incision and drainage. In few cases of active infection, however fistula needs to be ligated to prevent torrential bleed.

  Localized infections occurring after puncture of AV Fistula during dialysis are treated with appropriate antibiotics if signs of inflammation are present. AV Fistula infections are very rare and all respond well to antibiotic treatment which lasts for 4-6 weeks. Ligation of the AV Fistula is required only when it becomes a source of infective embolism to the lungs.

• Aneurysm-

  An aneurysm is a pathological enlargement of the blood vessel wall resulting from repetitive puncture. False aneurysms or pseudoaneurysm are hematomas located outside the vessel wall, formed due to a leaking hole in the artery, most often due to iatrogenic trauma - primarily repeated needle punctures.

  Colour Doppler ultrasound can differentiate false-aneurysm expansion from a hematoma, true dilated aneurysms (blood vessel), the presence of a thrombotic mass, which enables a decision to be made on possible surgical correction.

  Surgical intervention is recommended in pseudoaneurysms and aneurysms when there is a risk of perforation and ulceration, if there are episodes of bleeding or if the overlying skin is not healthy. This has to be treated surgically by excision of the mass, closure of fistula or leaking artery and making a new fistula if required usually in the same setting.

• Rupture-

  Repeated punctures of fistula for dialysis or infection leads to thinning of its walls which make it weaker and rupture of fistula may follow. If ruptured, the emergency surgical management is required to control the blood loss and either ligate the fistula or repair it and make a new AV Fistula at the same time.

  This is done by microvascular surgery done under microscope. After repair, extra care is taken to confirm patency of fistula and to maintain the blood flow. Blood thinning drugs are given for this.

• Stenosis-

  Significant stenosis of the vessel lumen is defined as a reduction by more than 50%. Clinical suspicion of stenosis is confirmed by the presence of several factors: reduced quality of dialysis, problems with puncture, such as prolonged bleeding after AVF puncture, pain in the area of the fistula or increased venous pressure.

  Thrombosis is a crucial cause of loss of function of an AVF. It usually occurs near a blockage in the area of anastomosis or vein of the fistula.

  High urea in blood increases levels of homocysteine or endogenous inhibitors of NO synthase, which could be directly toxic to the inner lining of the blood vessels. Vein wall distensibility is controlled by collagen, elastin and smooth muscle. There is accumulation of collagen fibers in place of smooth muscle cells in preaccess cephalic veins, causing a decrease in the elasticity of the vein wall. This process reduces the distensibility of the veins, and thus interferes with the proper maturation of the AVF. Stenosis may also be due to compression by an abscess or hematoma.

  Stenosis is diagnosed by measuring the peak systolic velocity in Doppler ultrasound. Values greater than 400 cm/s indicate the presence of stenosis; a monthly decline in flow by 20-25% is also considered significant for this type of complication. Angiography is a reliable technique for determining stenosis but is more expensive and technically demanding. Treatment involves balloon dilatation of the stenosis, stent implantation or surgical revision. Percutaneous transluminal angioplasty (PTA) in the treatment of AV Fistula stenosis improves fistula function and prolongs fistula survival in patients with shorter lesions ( <1 cm ), but restenosis remains the major problem.

• Congestive heart failure-

  Heart failure in patients with AVFs occurs only in individuals with previously chronic heart disease. Preliminary data show a trend towards left ventricular hypertrophy (LVH) in patients with an AVF. Heart failure is a medical emergency and is treated in intensive care setting. Medications to strengthen the pumping action of heart are given and to decrease the burden of work of blood pumping over the heart muscles is tried to reduce by giving medical treatment.