Diagnostic ultrasound ( PDFDrive )

316 PART II Abdominal and Pelvic Sonography
HYDRONEPHROSIS
he term hydronephrosis refers to dilatation of the collecting
system. Obstruction is oten present, but this is not always the
case. here are many causes of a dilated renal collecting system,
and ultrasound is the initial imaging modality of choice for the
majority of these assessments (except as discussed in the previous
section where noncontrast-enhanced CT may be used in the
initial assessment of acute renal colic). Initial sonographic evaluation
should include an assessment of the degree of dilatation,
appearance of surrounding renal parenchyma, assessment for
level of obstruction and any obstructing lesion. Numerous grading
systems for the assessment of the degree of hydronephrosis have
been proposed following Ellenbogen and colleagues’ original
article on the topic. 12 None has been readily adopted, however,
and most radiologists continue to use descriptive terminology
such as mild, moderate, and severe. 13
FIG. 9.7 Translabial Ultrasound of Female Urethra. Sagittal
sonogram shows the tubular hypoechoic urethra extending from the
bladder to the skin surface.
A practical pearl for the ultrasound evaluation of hydronephrosis
is to assess the degree of dilatation before and ater bladder
voiding. Hydronephrosis that persists ater voiding suggests an
anatomic obstruction. If collecting system dilatation diminishes
postvoiding, then one might consider nonobstructive pelvicaliectasis
(i.e., vesicoureteral relux). Most obstructing lesions are
located within the pelvis (ibroids, prostatic hypertrophy, ovarian
tumor, bladder tumor) and thus are obvious on sonographic
evaluation. When the pelvis is normal, the length of the ureter
should be assessed for dilatation and/or obstructing lesion. In
pregnancy, it is helpful to have the patient lie in the decubitus
position with the symptomatic side up to allow for the weight
of the uterus to move of of the ureter.
Over time the obstructed kidney will initially become enlarged.
Later, renal damage may occur with parenchymal atrophy and
blunting of calices.
In pregnancy, the urinary tract frequently is dilated. Smooth
muscle relaxation occurs as a result of elevated hormone levels.
Mass efect on the ureter may be caused by the enlarged uterus.
Because of the location of the ureters, the right ureter is frequently
more dilated than the let ureter. Physiologic dilatation of the
urinary tract in pregnancy is suggested when the distal ureters
taper at the sacral promontory. Pregnant patients are also at
increased risk for urinary tract infections (UTIs), which can
complicate the assessment. In addition, stone disease can occur
and this needs to be distinguished from the physiologic dilatation
associated with pregnancy.
In acute hydronephrosis of pregnancy, patients may present
with severe lank or lower abdominal pain radiating to the groin
due to ureteric obstruction. he obstruction usually occurs at
the level of the pelvic brim. Symptoms may improve with change
in posture with the patient in the lateral decubitus position,
symptomatic side up. In extreme cases, ureteral stunting may
be required. When severe overdistention syndrome occurs, rupture
of the urinary tract may occur, which can be identiied as luid
collection around the periphery of the kidney by ultrasound.
A
B
FIG. 9.8 Transrectal Ultrasound of Male Urethra. (A) Sagittal and (B) transverse sonograms show the urethra with calciications in the urethral
glands (arrows) surrounded by the echo-poor muscle of the internal urethral sphincter. B, Bladder; arrowhead, ejaculatory duct; S, seminal vesicles.
(Courtesy of Ants Toi, MD, Toronto Hospital.)