What is the medical term meaning distended blood vessel?

A distended blood vessel often causes a sac to form which is filled with blood. It is called an aneurysm if it occurs in an artery. Caused by distension or weakening of the vessel wall, it is a sign of disease of the vessels and may rupture. Veins also become distended such as in varicose veins where the vein is commonly swollen, twisted and lengthened as a result of poor circulation. It results in a lowered efficiency in returning blood to the heart.