Diagnostic ultrasound ( PDFDrive )

322 PART II Abdominal and Pelvic Sonography
A
B
FIG. 9.16 Congenital Megaureter. (A) Sagittal sonogram shows marked dilatation of the distal ureter up to the ureterovesical junction.
(B) Sagittal sonogram shows moderate midregion ureterectasis.
Aberrant renal arteries will be present if the vascular supply
from the lower levels of the aorta persists. Aberrant vessels can
compress the ureter anywhere along its course. Color Doppler
ultrasound may be useful to identify obstructing vessels crossing
at the UPJ.
Retrocaval Ureter
Retrocaval ureter is a rare but well-recognized congenital anomaly
with a 3 : 1 male predominance. Most patients present with pain
in the second to fourth decade of life. Normally, the infrarenal
inferior vena cava (IVC) develops from the supracardinal vein;
if it develops from the subcardinal vein, the ureter will pass
posterior to the IVC. he ureter then passes medially and
anteriorly between the aorta and IVC to cross the right iliac
vessels. It then enters the pelvis and bladder in a normal manner.
Sonography shows collecting system and proximal ureteral dilatation.
In easy-to-scan patients the compressed retrocaval ureter
may be identiied.
Anomalies Related to Bladder Development
Bladder Agenesis
Bladder agenesis is a rare anomaly. Most infants with bladder
agenesis are stillborn; virtually all surviving infants are female. 22
Many associated anomalies are oten present. At ultrasound, the
bladder is absent.
Bladder Duplication
Bladder duplication is divided into three types, as follows 16 :
Type 1: A complete or incomplete peritoneal fold separates the
two bladders.
Type 2: An internal septum divides the bladder. he septum
may be complete or incomplete and may be oriented in a
sagittal or coronal plane. here may be multiple septa.
Type 3: A transverse band of muscle divides the bladder into
two unequal cavities.
Bladder Exstrophy
Bladder exstrophy occurs in 1 in 30,000 live births, with a 2 : 1
male predominance. 16 Failure in development of the mesoderm
below the umbilicus leads to absence of the lower abdominal
and anterior bladder wall. here is a high incidence of associated
musculoskeletal, gastrointestinal, and genital tract anomalies.
hese patients have an increased (200-fold) incidence of bladder
carcinoma (adenocarcinoma in 90%). 16
Urachal Anomalies
Normally, the urachus closes in the last half of fetal life. 16 he
four types of congenital urachal anomalies, in order of frequency,
are as follows 16,23,24 (Fig. 9.17):
1. Patent urachus (50%)
2. Urachal cyst (30%)
3. Urachal sinus (15%)
4. Urachal diverticulum (5%)
Urachal anomalies have a 2 : 1 predominance in males. A
patent urachus is usually associated with urethral obstruction
and serves as a protective mechanism to allow normal fetal
development. A urachal cyst forms if the urachus closes at the
umbilical and bladder ends but remains patent in between. he
cyst is usually situated in the lower third of the urachus. here
is an increased incidence of adenocarcinoma. At ultrasound, a
midline cyst with or without internal echoes is seen superior to
the bladder. A urachal sinus forms when the urachus closes at
the bladder end but remains patent at the umbilicus. A urachal
diverticulum forms if the urachus closes at the umbilical end
but remains patent at the bladder. Urachal diverticula are usually
incidentally found. here is an increased incidence of carcinoma
and stone formation.