©Walter Rasmussen, R.D.C.S.
The abdominal aorta runs parallel to the inferior vena cava and in most cases is easily found by angling the face of the transducer from the inferior vena cava slightly toward the left side of the abdomen.
The abdominal aorta is located in such close proximity to the inferior vena cava that distinguishing characteristics must sometimes be carefully observed so that the two are not confused. One method for distinguishing the inferior vena cava from the rigid, pulsatile blood flow within the abdominal aorta is to observe for slow flowing blood flow with the subtle respiratory changes in vessel diameter and uneven changes in velocity and direction typically found within the inferior vena cava.
In some instances, a long segment of the abdominal aorta can be recorded, while in others, only a few centimeters will be visible. As in all of the abdominal views, having the patient take in and retain a deep breath will in most cases, greatly improve the image. Patients with obesity, tight, spherical abdomens or post-abdominal surgery can be very difficult to image and a notation should be made if the abdominal aorta is not visualized.
Color Doppler and PW Doppler of the abdominal aorta are used to detect blood flow reversal for moderate vs severe aortic regurgitation. These modalities can also help to distinguish between the abdominal aorta and the inferior vena cava when their appearance alone on 2D images is not sufficient. Abdominal aortic Doppler demonstrates pulsatile blood flow whereas venous blood flow in the inferior vena cava is continuous, uneven and connected with respiration.
Above: Color Doppler of the abdominal aorta will help to assess for flow reversal in aortic regurgitation and false lumen in abdominal aortic dissection.
PW Doppler of the abdominal aorta is used to detect blood flow reversal in patients with severe aortic regurgitation.When performing PW Doppler of this area, try to place the sample volume as parallel to flow as possible. If necessary, slide the transducer superiorly or inferiorly to achieve more parallel Doppler angle to flow as in the above illustration.