Diagnostic ultrasound ( PDFDrive )

CHAPTER 9 The Kidney and Urinary Tract 321
Ureteropelvic Junction Obstruction
UPJ obstruction is a common anomaly with a 2 : 1 male predominance.
he let kidney is afected twice as frequently as the
right kidney. UPJ obstruction is bilateral in 10% to 30% of cases. 20
Most adult patients present with chronic, vague, back or lank
pain. Symptomatic patients and those with complications, including
superimposed infection, stones, or impaired renal function,
should be treated. Patients have an increased incidence of contralateral
multicystic dysplastic kidney and renal agenesis. Most
idiopathic UPJ obstructions are thought to be functional rather
than anatomic. 20 Histologic evaluation of afected specimens has
demonstrated excessive collagen between muscle bundles, deicient
or absent muscle, and excessive longitudinal muscle. 20 Occasionally,
intrinsic valves, true luminal stenosis, and aberrant arteries are
the cause of obstruction. At ultrasound, hydronephrosis is present
to the level of the UPJ (Fig. 9.15). Marked ballooning of the
renal pelvis is oten shown, and if long-standing, there will be
associated renal parenchymal atrophy. he caliber of the ureter,
on the other hand, is normal. Careful evaluation of the contralateral
kidney should be performed to exclude associated anomalies.
Congenital Megacalices
Congenital megacalices refer to typically unilateral, nonobstructive
enlargement of the calices. It is nonprogressive; overlying
parenchyma and renal function are maintained. Infection and
stone formation are increased because of caliceal enlargement.
he exact pathogenesis is speculative; the most common association
is with primary megaureter. 21 At ultrasound, numerous
enlarged clubbed calices are shown. Papillary impressions are
absent, and cortical thickness is maintained.
Congenital Megaureter
Megaureter (congenital megaureter, megaloureter) results in
functional ureteric obstruction. he most distal segment of ureter
is aperistaltic: focal ureteral lack of peristalsis results in a wide
spectrum of indings, from insigniicant distal ureterectasis to
progressive hydronephrosis/hydroureter. As with UPJ obstructions,
men are afected more oten, and the let ureter is typically
involved. 20 Bilateral involvement has been demonstrated in 8%
to 50% of patients. he classic inding at ultrasound is fusiform
dilatation of the distal third of the ureter (Fig. 9.16). Depending
on the severity, associated pyelocaliectasis may or may not be
present. Calculi may form just proximal to the adynamic segment.
FIG. 9.14 Small Bilateral Ureteroceles. Transverse transvaginal
sonogram demonstrates two small cystic structures related to the bladder
wall. With the probe in the vagina, the bladder trigone and the ureteric
oriices are shown in the near ield of the transducer.
Anomalies Related to Vascular
Development
Aberrant Vessels
As it ascends during embryologic development, the kidney derives
its blood supply from successively higher levels of the aorta.
A
B
FIG. 9.15 Ureteropelvic Junction Obstruction. (A) Sagittal and (B) transverse sonograms demonstrate marked ballooning of the renal pelvis
with associated proximal caliectasis.