Diagnostic ultrasound ( PDFDrive )

CHAPTER 52 The Pediatric Urinary Tract and Adrenal Glands 1811
A
B
C
FIG. 52.50 Postbiopsy Pseudoaneurysms. (A) Longitudinal grayscale
image of a renal allograft shows two rounded lower-pole anechoic
cystic structures (arrows). (B) Color Doppler imaging reveals a “yin-yang”
sign caused by swirling blood low within the upper pseudoaneurysm
(arrows). (C) Spectral Doppler analysis depicts disordered blood low
above and below the baseline. Arrowhead indicates lower
pseudoaneurysm.
FIG. 52.51 Lymphocele. Longitudinal gray-scale image demonstrates
two anechoic luid collections adjacent to the upper and lower poles of
a renal allograft (*). The lower collection is separate from the bladder
(not shown) and contains a small amount of echogenic, dependent
debris (arrow).
Depending on whether the allograt is located intraperitoneally
or extraperitoneally, the leak can result in a localized perinephric
urinoma or urine ascites. 130 A urinoma will usually appear as
an anechoic, well-circumscribed, perinephric luid collection. If
clinically indicated, 99m Tc-mertiatide renal scintigraphy, contrastenhanced
CT, or magnetic resonance urography can be performed
to diferentiate urinoma from seroma or lymphocele.
Urinary tract obstruction usually becomes apparent in the
irst few months ater transplantation, and in general manifests
clinically with nonspeciic grat dysfunction. About 50% of the
time, obstruction is related to an ischemic stricture at the
ureteroneocystostomy. Other causes include midureteral stenosis,
stone, blood clot, fungus ball, and extrinsic compression.
Midureteral stenosis usually occurs in the setting of chronic
rejection. Some degree of hydronephrosis is commonly identiied
ater renal transplantation in both children and adults as a result
of denervation with loss of muscle tone of the donor collecting
system. he presence or absence of mild to moderate collecting
system dilation has been shown to correlate poorly with the
presence or absence of urinary tract obstruction in the posttransplant
patient. 154 However, sonographic depiction of moderate
to severe hydronephrosis and hydroureter that increase progressively
over time warrants further evaluation for posttransplant
urinary tract obstruction. MAG3 renal scintigraphy or magnetic
resonance urography can be performed, with the more invasive
method of percutaneous antegrade urography used to localize
the site of obstruction. A nephrostomy tube can be placed for
purposes of urinary tract decompression and to permit stent
placement or balloon ureteroplasty. 130
Vesicoureteral relux (VUR) has been documented in
approximately one-third to one-half of children ater renal
transplantation. 155,156 However, the presence of VUR does not
appear to be associated with either an increased frequency of
posttransplant urinary tract infection or decreased long-term
grat function. 149,156 Patients with VUR into the transplant kidney
usually have an underlying urologic abnormality, most commonly
PUVs. 157,158
Allograt infection may manifest as pyelonephritis, perinephric
or parenchymal abscess, pyonephrosis, or fungus ball. Although