Diagnostic ultrasound ( PDFDrive )

660 PART II Abdominal and Pelvic Sonography
A
B
C
D
FIG. 18.43 Renal Artery Stenosis: Anastomosis. (A) Color Doppler ultrasound shows focal area of narrowing and aliasing at the anastomosis
(arrows). (B) Spectral Doppler at the anastomosis shows elevated angle-corrected velocity of 775.4 cm/sec. (C) Renal arterial angiogram conirms
stenosis at the anastomosis (arrow). (D) Angiogram performed after angioplasty shows resolution of the anastomotic stenosis.
hilum, where the ureteral branch originates. 46 Other causes
of ureteral obstruction include strictures from iatrogenic
injury, intraluminal lesions (e.g., stones, blood clots, sloughed
papillae), perigrat ibrosis, and ureteral kinking (Figs. 18.47
and 18.48). Extrinsic compression of the ureter from peritransplant
collections can also result in collecting system
obstruction.
Patients with renal transplants are at higher risk for stone
development compared with the general population. In approximately
15% of these patients, the stone development is related
to hypercalcemia. Because the transplant is denervated, patients
with stone-related collecting system obstruction may not have
typical symptoms of renal colic. 54
Evaluation of the collecting system with fundamental grayscale
imaging may be diicult because of side-lobe and scatter
artifact, which can potentially obscure optimal evaluation of
the calyceal system and ureter. Harmonic imaging, however,
uses a narrower ultrasound beam with smaller side lobes and
is less susceptible to scatter artifact. hese parameters make
harmonic imaging ideal for evaluating anechoic structures,