Diagnostic ultrasound ( PDFDrive )

656 PART II Abdominal and Pelvic Sonography
A B C
D E F
FIG. 18.38 Renal Transplant-Related Infections. (A) Perirenal Candida abscess. Transabdominal sagittal scan shows abscess (A) abutting
the lower pole of the transplant kidney. (B) and (C) Subcapsular abscess on ultrasound and CT. Note the heterogeneous abscess (A) with gas
(arrow) compressing the kidney (K). (D) and (E) Ureteritis. Sagittal sonograms of proximal (D) and midline (E) ureter show inlamed echogenic
periureteral fat (arrows) secondary to an infected ureteral stent (arrowhead). (F) Cystitis. Transverse sonogram shows internal echoes and luid-debris
level (arrow) in urinary bladder, secondary to cystitis. Arrowheads show thickened bladder wall.
and show a very slightly higher rate of renal artery stenosis However, high velocities in the renal artery may be secondary
compared with those renal allograts with a single artery. Stenosis to changes in the external iliac artery. herefore the renal
may occur in one of three regions of the transplanted artery: artery–external iliac artery PSV ratio can be calculated to
the donor portion (Fig. 18.41), most frequently observed in determine if renal artery velocity measurements are a result of
end-to-side anastomoses and thought to arise from either rejection narrowing or high low rates from the external iliac artery. A
or diicult surgical technique; the recipient portion (Fig. 18.42), renal artery–external iliac artery PSV ratio greater than 1.8:1 is
which is more uncommon and usually the result of intraoperative suggestive of renal artery stenosis. 54,62 In addition, within the
clamp injury or intrinsic atherosclerotic disease; and the anastomosis
(Fig. 18.43), which is more frequent in end-to-end observed in the intraparenchymal arteries in patients with renal
renal parenchyma, a tardus-parvus spectral waveform can be
anastomoses and is directly related to surgical technique or may artery stenosis. 46,57 If no low abnormality is detected within the
be secondary to rejection. 54,58-60
main renal artery ater color and spectral Doppler interrogation,
Initially, color Doppler ultrasound should be used to determine signiicant stenosis can be excluded. 63
the location of the anastomosis, as well as to document focal
regions of aliasing, which would indicate the presence of highvelocity
turbulent low and serve as a guide for meticulous spectral
interrogation. A spectral tracing should then be obtained at the Doppler Criteria for Renal Artery Stenosis
anastomosis and in any area where color aliasing is detected to
determine the PSV in that region.
Color aliasing at the stenotic segment
he upper limit of normal for arterial PSV is unclear. Assigning Distal turbulent low
a PSV upper limit of 200 cm/sec for diagnosing renal artery Peak systolic velocity > 250 cm/sec
stenosis may result in a relatively high false-positive rate. hus Velocity gradient between the renal artery and external
some authors have suggested using an arterial threshold PSV of iliac artery greater than 1.8:1
250 cm/sec for the diagnosis of renal artery stenosis. 54,61