Page 193 - Libro 2

11 — Ultrasound Assessment of Arterial Bypass Grafts
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Figure 11-7 An ultrasound image of a distal anastomosis to a posterior tibial artery. (Image courtesy of Phillip J. Bendick, PhD RVT, Royal Oak, MI.)
absence of blood flow within an incidental finding. Multiple scanning planes should be used to fully document the additional pathology. Proximity to the bypass graft is also important to note, particularly in the event of an abscess.
A
C
PITFALLS
This examination can be slightly limited in a very obese patient. A bypass graft that is anatomically placed and tunneled deeply will necessitate the use of lower frequency transducers in order to penetrate deep enough to visualize the graft; however, this will result in poorer resolution. Dressings, skin staples, and sutures will also limit accessibility of portions of the bypass grafts to the ultrasound examination.
DIAGNOSIS
There are three components to analysis of the data obtained from ultrasound: the B-mode or grayscale image, the spectral Doppler waveform (which is the primary source of numerical data used to classify disease), and the color flow image.
GRAYSCALE FINDINGS
The B-mode or grayscale image should be closely examined for disease. The walls of a vein graft ap- pear smooth and uniform. Figure 11-9 illustrates the
B
Figure 11-8 Spectral Doppler tracing through the distal portion of a bypass and outflow artery: (A) a distal bypass, (B) a distal anastomosis, and (C) an outflow artery.