Diagnostic ultrasound ( PDFDrive )

1362 PART IV Obstetric and Fetal Sonography
“prune belly” syndrome. Typically, the bladder is very large and
thin walled. he posterior urethra is usually not dilated, and
there is no keyhole sign. 200 It is very diicult to diferentiate this
condition from posterior urethral valves, although the appearance
of the bladder and urethra may be helpful. he ureters are tortuous
and dilated, with bilateral hydronephrosis. If oligohydramnios
is present, it is diicult to demonstrate undescended testes. Other
abnormalities may be present, including congenital heart disease,
intestinal malrotation, and musculoskeletal deformities.
Megalourethra is characterized by a congenital deiciency of
the mesodermal tissues of the phallus, with dilation of the penile
urethra and enlargement of the penis. his condition has been
classiied into two types, fusiform and scaphoid urethra, but it
is preferable to consider it as a spectrum. Urinary stasis in the
dilated penile urethra results in functional obstruction of the
UT. he prenatal sonographic indings include those of LUTO,
with dilation and elongation of the penile urethra 201,202 (Fig. 39.36,
Video 39.9). Associated malformations of the UT include urethral
atresia, posterior urethral valves, prune belly syndrome, and
horseshoe kidney. Abnormalities involving the GI tract and spine
and VACTERL association have been reported. he prognosis
depends on the degree of renal dysfunction and the severity of
associated anomalies. Survivors are at risk of renal insuiciency,
impotence, and infertility.
Megacystis-microcolon–intestinal hypoperistalsis syndrome
(MMIHS) is a rare, nonobstructive cause of megacystis with a
4 : 1 female predominance. he syndrome is characterized by the
presence of nonobstructive bladder distention, intestinal
B
A
B
C
FIG. 39.36 Megacystis and Megalourethra. (A) Oblique
scan of the fetal pelvis at 21 weeks’ gestation shows a dilated
urinary bladder (B) with thick walls (calipers). (B) Transverse view
of the perineum shows a severely dilated penile urethra (arrow).
(C) Postmortem photograph of the fetus at 23 weeks’ gestation
shows enlarged penis. The penile urethra was patent (not shown).
(C courtesy of Sarah Keating, MD, Department of Pathology and
Laboratory Medicine, Mount Sinai Hospital, Toronto.) See also
Video 39.9.