Ultrasound should be considered as the primary procedure of choice in the evaluation of the abdominal aorta. It is noninvasive and does not require injection of contrast material. Both normal and abnormal ultrasonic aortic patterns are usually so typical that independent confirmation is not needed unless surgery is anticipated. In emergency situations involving rupture or dissection, the detection of an aneurysm by ultrasound often dramatically shortens the time interval between the emergency admission and actual surgery. The established uses for aortosonography are as follows: 1. Detection of a normal aorta. 2. Demonstration of an aneurysm (diffuse or localized). 3. Determination of its size, including both internal and external diameters. 4. Evaluation of internal echo patterns (clot or dissection). 5. Detection of lumen narrowing or occlusion. 6. Determination of aneurysm extension into the iliacs or thoracic aorta. 7. Evaluation of the major branches of the aorta. 8. Demonstration of other vessels such as the vena cava and portal vein as well as their branches. 9. Detection and differentiation of masses misdiagnosed as aneurysms. 10. Serial evaluation of aneurysms not having surgery to detect any change in size or internal pattern.