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Definition

noun

Abbreviation for arteriovenous malformation, a localized or diffuse vascular lesion characterized by a tangled collection of arteries and veins connected by one or more fistulas (abnormal communications) due to the lack of a capillary network that normally connects these vessels, thus, resulting in blood from artery flowing directly to the vein.

Supplement

When localized it is often seen on the head and neck as light vascular stains at birth and when diffuse it is seen on the chest and abdomen or on a limb that only becomes apparent late in childhood. It may also occur in brain, lung, liver and colon, and cause headaches, seizures, or bleeding (subarachnoid haemorrhage).