Diagnostic ultrasound ( PDFDrive )

662 PART II Abdominal and Pelvic Sonography
A
B
C
D
FIG. 18.45 Renal Vein Thrombosis. (A) Sagittal sonogram shows increased cortical echogenicity with a coarse echotexture. (B)-(D) Spectral
Doppler ultrasound images of (B) cortical arteries, (C) renal sinus arterial branches, and (D) main renal artery show reversal of low in diastole. No
venous low was detected in the transplant.
renal perfusion caused by the large shunt. In these patients,
treatment usually involves percutaneous embolization therapy. 44
Gray-scale ultrasound may not reveal small AVMs. Color
Doppler sonography shows a focal region of aliasing with myriad
intense colors, oten associated with a prominent feeding artery
or draining vein. Turbulent low within the AVM produces
vibration of the perivascular tissues, resulting in these tissues
being assigned a color signal outside the borders of the renal
vasculature. Spectral Doppler ultrasound is typical of that for
all AVMs, with low-resistance, high-velocity low and diiculty
diferentiating between artery and vein within the malformation.
If a dominant draining vein is detected, the waveform may be
pulsatile or arterialized 58,68-70 (Fig. 18.51, Video 18.3).
On color Doppler ultrasound, focal regions of cortical dystrophic
calciications or small stones can mimic an AVM by
producing an intense color signal known as a twinkling artifact. 71
hese artifacts can be diferentiated from a true AVM on spectral
tracing because both calciications and stones produce characteristic
linear bands on spectral interrogation. In our clinical
experience, we have also observed a linear band of color posterior
to these regions of calcium that extend to the limits of the color
box. We have not observed this phenomenon with AVMs and