Diagnostic ultrasound ( PDFDrive )

366 PART II Abdominal and Pelvic Sonography
intraperitoneal rupture, or a combination. Sonography is usually
not helpful in the assessment of these injuries, except to identify
large luid collections or free intraperitoneal luid.
FIG. 9.79 Renal Laceration. Transverse sonogram shows capsular
disruption and mixed-echogenicity perirenal hematoma. (Courtesy of
John McGahan, MD.)
FIG. 9.80 Subcapsular Hematoma After Renal Biopsy. Note
compression of kidney (arrowheads) by large, hyperechoic subcapsular
hematoma.
Doppler sonography may be helpful in the assessment of vascular
pedicle injuries. As use of CEUS becomes more prevalent, there
may be a role for CEUS in the initial bedside assessment and
follow-up of renal injuries in critically ill patients. 266,267
Ureteral Injuries
Traumatic injury of the ureter is most oten a complication of
either gynecologic (70%) or urologic (30%) surgery. 268 Blunt and
penetrating injuries are much less common. Sonography is not
useful in the assessment of these injuries, except to detect sizable
luid collections and hydronephrosis.
Bladder Injuries
Bladder injury may be the result of blunt, penetrating, or iatrogenic
trauma. Bladder injury may result in extraperitoneal or
VASCULAR ABNORMALITIES
Renal Vascular Doppler Sonography
he number and size of arteries supplying a kidney are quite
variable. Duplex and color Doppler imaging are able to demonstrate
both normal and abnormal renal blood low. Normal low
within the renal artery and its branches has a “low resistance”
perfusion pattern, with continuous forward blood low during
diastole. Several Doppler parameters have been used to describe
changes in Doppler arterial spectra that may accompany renal
disease. he most common parameter is the RI. Keogan et al. 269
recommend averaging a number of RI measurements in a kidney
before a single representative average is reported. Most sonographers
consider an RI of 0.7 to be the upper threshold of normal
in adults, although renal RIs greater than 0.7 may be seen in
children younger than 4 years of age and in older patients, despite
normal renal function. 270-272 Mostbeck et al. 273 also showed how
the RI varies with heart rate and can range from 0.57 ± 0.06
(pulse, 120/min) to 0.70 ± 0.06 (pulse, 70/min).
Despite this variability, early literature indicated the potential
of Doppler for improving the sonographic assessment of renal
dysfunction. Changes in intrarenal spectra (quantiied using
RI) were associated with acute or chronic urinary obstruction,
several intrinsic native renal diseases, renal transplant rejection,
and renal vascular disease. Less favorable results in follow-up
studies and discouraging clinical experience prompted most
radiologists to abandon the RI. Studies show that the RI varies
as a result of driving pulse pressures, which explains Mostbeck’s
observation of rate-dependent changes in RIs, as well as changes
in vascular/interstitial compliance. 112-114
Renal Artery Occlusion and Infarction
Renal artery occlusion may be caused by either emboli or in situ
thrombosis. he degree of renal insult depends on the size and
location of the occluded vessel. If the main renal artery is occluded,
the entire kidney will be afected, whereas segmental infarction
and focal infarction occur with peripherally located vascular
occlusion. he acutely infarcted kidney is oten normal appearing
at gray-scale sonography. However, no low within the kidney
is shown at duplex and color/power Doppler examination (Fig.
9.81). Segmental or focal infarction may appear as a wedge-shaped
mass indistinguishable from acute pyelonephritis. With time,
an echogenic mass 274 or scar may form. With chronic occlusion,
a small, scarred, end-stage kidney will be seen.
Arteriovenous Fistula and Malformation
Abnormal arteriovenous communications can be acquired (75%)
or congenital (25%). Acquired lesions are usually iatrogenic,
although spontaneous abnormal arteriovenous communications
may occur with eroding tumors. Most acquired lesions consist
of a single, dominant feeding artery and a single, dominant
draining vein. Congenital malformations consist of a tangle of