This examination is commonly used to diagnose a variety of blood vessel diseases. You may need to undergo DSA to diagnose obstructive vascular diseases that are caused by blockages or narrowing of the lumen of arteries and veins. Your doctor may also request a DSA to diagnose a brain aneurysm, bleeding vessels, arteriovenous malformations (abnormal connections between arteries and veins) and to assess the vascularity (blood supply) of cancerous tumours. Angiography also provides a visual guide for interventional procedures needed to unblock or reopen blocked arteries. These procedures include angioplasty, arterial stenting, nephrostomy (opening created between kidney and skin) and biliary (bile duct) procedures.