arteriovenous fistula - definition of arteriovenous fistula in the Medical dictionary - by the Free Online Medical Dictionary, Thesaurus and Encyclopedia.

Arteriovenous Fistula

Definition

An arteriovenous fistula is an abnormal channel or passage between an artery and a vein.

Description

An arteriovenous fistula is a disruption of the normal blood flow pattern. Normally, oxygenated blood flows to the tissue through arteries and capillaries. Following the release of oxygen in the tissues, the blood returns to the heart in veins. An arteriovenous fistula is an abnormal connection of an artery and a vein. The blood bypasses the capillaries and tissues, and returns to the heart. Arterial blood has a higher blood pressure than veins and causes swelling of veins involved in a fistula. Although both the artery and the vein retain their normal connections, the new opening between the two will cause some arterial blood to shunt into the vein because of the blood pressure difference.

Causes and symptoms

There are two types of arteriovenous fistulas, congenital and acquired. A congenital arteriovenous fistula is one that formed during fetal development. It is a birth defect. In congenital fistulas, blood vessels of the lower extremity are more frequently involved than other areas of the body. Congenital fistulas are not common. An acquired arteriovenous fistula is one that develops after a person is born. It usually occurs when an artery and vein that are side-by-side are damaged and the healing process results in the two becoming linked. After catheterizations, arteriovenous fistulas may occur as a complication of the arterial puncture in the leg or arm. Fistulas also form without apparent cause. In the case of patients on hemodialysis, physicians perform surgery to create a fistula. These patients receive many needle sticks to flush their blood through dialysis machines and for routine blood analysis testing. The veins used may scar and become difficult to use. Surgery is used to connect an artery and vein so that arterial blood pressure and flow rate widens the vein and decreases the chance of blood clots forming inside the vein.

The main symptoms of arteriovenous fistulas near the surface of the skin are bulging and discolored veins. In some cases, the bulging veins can be mistaken for varicose veins. Other fistulas can cause more serious problems depending on their location and the blood vessels involved.

Diagnosis

Using a stethoscope, a physician can detect the sound of a pulse in the affected vein (bruit). The sound is a distinctive to-and-fro sound. Dye into the blood can be tracked by x ray to confirm the presence of a fistula.

Treatment

Small arteriovenous fistulas can be corrected by surgery. Fistulas in the brain or eye are very difficult to treat. If surgery is not possible or very difficult, injection therapy may be used. Injection therapy is the injection of substances that cause the blood to clot at the site of the injection. In the case of an arteriovenous fistula, the blood clot should stop the passage of blood from the artery to the vein. Surgery is usually used to correct acquired fistulas once they are diagnosed.

Resources

Books

Alexander, R. W., R. C. Schlant, and V. Fuster, eds. The Heart. 9th ed. New York: McGraw-Hill, 1998.

Berkow, Robert, ed. Merck Manual of Medical Information. Whitehouse Station, NJ: Merck Research Laboratories, 2004.

Braunwald, E. Heart Disease. Philadelphia: W. B. Saunders Co., 1997.

Key terms

Congenital — Present at the time of birth.

fistula /fis·tu·la/ (fis´tu-lah) pl. fistulas, fis´tulae [L.] an abnormal passage between two internal organs or from an internal organ to the body surface.

Various types of fistulae, designated according to site or to the organs with which they communicate. (A), Genitourinary fistulae; (B), anal fistulae.

anal fistula one from the anus to the skin, sometimes communicating with the rectum.

arteriovenous fistula

1. one between an artery and a vein.

2. a surgically created arteriovenous connection that provides a site of access for hemodialysis tubing.

blind fistula one open at one end only, opening on the skin (external blind f.) or on an internal mucous surface (internal blind f.) .

branchial fistula a persistent pharyngeal groove (branchial cleft).

cerebrospinal fluid fistula one between the subarachnoid space and a body cavity, with leakage of cerebrospinal fluid, usually as otorrhea or rhinorrhea.

colonic fistula one connecting the colon with the body surface or another organ.

craniosinus fistula one between the cerebral space and one of the sinuses, permitting escape of cerebrospinal fluid into the nose.

enterovesical fistula one connecting the urinary bladder with some part of the intestines.

fecal fistula a colonic fistula that discharges feces on the body surface.

gastric fistula one communicating with the stomach, either pathologically or surgically created through the abdominal wall.

genitourinary fistula one between two organs of the urogenital system or between one of those organs and some other system.

incomplete fistula blind f.

intestinal fistula one communicating with the intestine; sometimes surgically created through the abdominal wall.

perilymph fistula rupture of the round window with leakage of perilymph into the middle ear, causing sensorineural hearing loss.

pulmonary arteriovenous fistula a congenital fistula between the pulmonary arterial and venous systems, so that unoxygenated blood enters the systemic circulation.

salivary fistula one communicating with a salivary duct.

tracheoesophageal fistula one connecting the trachea and esophagus, either pathologically or created surgically to restore speech after laryngectomy.

umbilical fistula one communicating with the colon or the urachus at the umbilicus.

arteriovenous fistula

An abnormal communication between an artery and a vein, usually resulting in the formation of an arteriovenous aneurysm.

arteriovenous fistula,

an abnormal communication between an artery and vein. It may occur congenitally or result from trauma, infection, arterial aneurysm, or a malignancy. A continuous murmur and palpable thrill may be detected over the fistula and may be obliterated by compressing the feeding artery; this maneuver may slow the heartbeat (Branham's sign). Chronic arteriovenous fistulas may cause varicosities, cutaneous ulcers, and cardiac enlargement resulting from high-output heart failure. A congenital fistula may result in a cavernous hemangioma. If an arteriovenous fistula is limited in size and is accessible, it can be treated by surgical excision. An arteriovenous fistula is often created surgically to provide vascular access for hemodialysis.

fistula (fis´tyool

n an abnormal tract connecting two body surfaces or organs or leading from a pathologic or natural internal cavity to the surface. The tract may be lined with epithelium.

Fistula.

fistula, alveolar,

n See parulis.

fistula, arteriovenous,

n See shunt, arteriovenous.

fistula, branchial,

n a fistula associated with a branchial cyst; usually seen on the lateral surface of the neck.

fistula, dental,

n See parulis.

fistula, of lip,

n a congenital malformation in which there is a deep pit or fistula on the mucosa of the lip; often bilateral and usually found on the lower lip.

fistula, oroantral,

n an opening between the maxillary sinus and the oral cavity, most often through a tooth socket. See also fistula.

fistula, orofacial,

n an opening between the cutaneous surface of the face and the oral cavity.

fistula, oronasal,

n an opening between the nasal cavity and the oral cavity.

fistula, salivary,

n an opening between a salivary duct and/or gland and the cutaneous surface or into the oral cavity through other than the normal anatomic pathway.

arteriovenous

both arterial and venous; pertaining to both artery and vein.

arteriovenous anastomosis

a direct connection between an artery and a vein that acts as a shunt to bypass the capillary bed. These occur in areas where a high volume blood supply is needed only intermittently, e.g. the intestine.

arteriovenous fistula

an abnormal communication between an artery and a vein; includes cardiac defects such as ventricular septal defects and patent ductus arteriosus. Peripheral fistulae, especially in the extremities, may be localized, usually acquired and the result of trauma, while congenital defects tend to be more diffuse, involving a network of anastomosing vessels.

The effects of arteriovenous fistulae are variable, depending on their location and the amount of blood carried. Within the liver they usually connect the hepatic artery and portal vein, causing portal hypertension and ascites. Small peripheral fistulae may be noticeable only as warm, reducible swellings, often with an audible thrill, or give rise to edema distal to the site. More severe effects are also possible.

pulmonary arteriovenous fistula

a congenital anomalous communication between the pulmonary arterial and venous systems, allowing unoxygenated blood to enter the systemic circulation.

arteriovenous fistula

Surgery 1 Arteriovenous shunt, see there 2. A post-traumatic anastomosis between arteries and veins, which bypasses the capillary bed

Patient discussion about arteriovenous fistula.

Q. I developed an AV Fistula after a heart catherization procedure. I am bleeding through the tissues in left arm I am on coumadin, but currently have a lower than usual INR. Corrective surgery was scheduled for yesterday, but had to be delayed. I am concerned that I have a large amount of blood (dark red) bleeding though the tissues right under the skin in my left arm. Should I seek immediate medical attention? The bleeding is over approximately a 3 and 1/2" area on my left arm. Came about in a period of a few minutes.

A. well, you are on blood thinners. i wouldn't take the chance. i mean- i'm not sure i follow what is happening over there. it could be a severe problem or nothing. i would let a doctor check it out. the worse thing that could happen is you wasting a day at the hospital, on the other end of that scenario- you can end up dead. i would go with the first one.