Fetal Megacystis

Abstract

The purpose of our retrospective observational series was to determine whether the sonographic characteristics of fetal megacystic bladders can be used to reliably establish the most likely diagnosis in fetuses with this condition. The sonographic records of pregnant patients referred to our institutions over a 10-year period who were found on initial 2-dimensional sonography to be carrying fetuses with megacystis were examined for evidence of a keyhole sign, bladder thickness, amniotic fluid index, and fetal sex. When available, 3-/4-dimensional sonography, Doppler angiography, tomographic ultrasound imaging, virtual organ computer-aided analysis, and automatic volume calculation were used as part of the detailed fetal anatomic survey. Twenty fetuses with megacystis were identified. Seventeen were male; 2 were female; and 1 had ambiguous genitalia. All male fetuses with megacystis originally had a diagnosis of prune belly syndrome. The diagnosis for 10 male fetuses with a keyhole sign was changed to megacystis secondary to posterior urethral valves. The fetus with ambiguous genitalia had prune belly syndrome. One of the female fetuses had a diagnosis of urethral atresia, and the diagnosis for the other female fetus was megacystis-microcolon-intestinal hypoperistalsis syndrome. In conclusion, in fetuses with megacystic bladders, it is possible to distinguish between cases with prune belly syndrome, posterior urethral valves, urethral atresia, and megacystis-microcolon-intestinal hypoperistalsis syndrome by a detailed anatomic survey using 2- and 3-/4-dimensioinal sonographic techniques.

Microtomographic Analysis of Lower Urinary Tract Obstruction

“…Newer forms of ultrasonography may provide higher resolution [21] while pathologists continue to exercise great care in postmortem workups. The anatomic delineation of bladder outlet obstruction should further the understanding of pathogenesis and etiology.…”

A case of ultrasound-guided prenatal diagnosis of prune belly syndrome in Papua New Guinea – implications for management

“…During the same ultrasound examination the distended bladder measured 4.6 × 3.6 × 4.8 cms. The keyhole sign [9] was not observed, fetal sex could not be determined but there was evidence of concomitant ureteric dilatation (not shown). Umbilical artery flow indices were abnormal for gestational age on Doppler performed at second scan: the systolic:diastolic ratio (2.37), resistance index (0.55) and pulsatility index (0.77) were all below the 5 th percentile using standard reference charts [23-25].…”

“…Other fetal malformations which may be associated with PBS include gastrointestinal, cardiac, pulmonary and limb abnormalities [8]. Prenatal ultrasound features can include oligo- or anhydramnios, megacystis, hydronephrosis, and hyperechogenic kidneys [9]. To date, a clear genetic basis for PBS has not been established and the aetiology of the syndrome is unknown [10].…”

“…To date, a clear genetic basis for PBS has not been established and the aetiology of the syndrome is unknown [10]. It is thought that PBS arises from a defect in the intermediate and lateral plate mesoderm development during the 6 th to 10 th week of gestation, resulting in clinical abnormalities [9,11,12]. …”

“…In high-income countries, most cases of PBS are diagnosed antenatally through ultrasound, and confirmed at birth [9,13]. By contrast, in resource-limited settings such as Papua New Guinea (PNG) prenatal diagnosis of congenital abnormalities remains unreported, and documentation of congenital abnormalities observed after delivery is rare [14-17].…”