Early prenatal diagnosis of the OEIS complex with different appearance in early compared with late pregnancy before spontaneous rupture of the cloacal membrane

Abstract

The OEIS complex is a rare variant of the exstrophy–epispadias complex. It is most often diagnosed in second trimester screening by typical sonographic features of omphalocele together with exstrophy of the fetal bladder, imperforate anus and spinal anomalies that have created its acronym. Firsttrimester sonography is now widely accepted not only as screening for aneuploidies but also for major structural anomalies. The typical feature of each disorder must be kept in mind as several structural defects show different sonographic features in the first compared with the second trimester. For example, whereas spina bifida is indirectly diagnosed by scalloping of the frontal bones (‘lemon sign’) and caudal displacement of the cerebellum (‘banana sign’) in the second trimester, the characteristic indirect feature of spina bifida in first trimester is the absence of the intracranial translucency and the displacement of the brain stem, respectively. Furthermore, direct visualization of the spinal defect in early gestation is difficult, in particular due to the small size of the cele during the first trimester. The same is true for fetal exencephaly–anencephaly: in the first trimester, the cerebral lobes are present and floating in the amniotic fluid, resembling the face of Mickey Mouse in the coronal plane; whereas in the second trimester, lack of any tissue and cranium above the level of the orbits due to perishing of the fetal brain similar a frog head or frog eye appearance by the bulging orbits. Similar, cloacal extrophy and lower urinary tract obstruction (LUTO) show another clinical picture in the first trimester than in the second trimester, as both present as large cystic mass in the abdomen in the first trimester and change appearance upon their rupture. A 35-year-old gravida II/para I was referred for fetal assessment at 14 + 1weeks of gestation due to a large cystic mass initially diagnosed in 12 + 5weeks of gestation in the lower abdomen of the fetus (Figure 1A). Medical history and course of the pregnancy had been uneventful. Detailed ultrasound examination of the fetus revealed inappropriate fetal growth (BPD: 26.1mm; CRL: 69.8mm) and a 41 × 34mm large cystic structure in the lower abdomen with an intact lower abdominal wall. The membrane of the cyst was very thin similar to an amnion membrane and occupied the entire abdomen of the fetus pushing the adjacent organs cranially (Figure 1A). No urinary bladder could be visualized. Amniotic fluid was in normal range. Differential diagnoses included LUTO due to posterior urethral valves, a nonruptured cloacal membrane and an amniotic band syndrome affecting the infraumbilical part of the body. Vesicocentesis is a useful diagnostic procedure for evaluation of the tubular renal function and has been shown to be a sufficient treatment in some case of megacystis. Hence, puncture of the cyst with drainage of 25ml fluid was performed revealing features of fetal urine (sodium level: 118mmol/L; chloride level: 105mmol/L; β2-microglobulin level: 6.40mg/L; cystatin C: 0.96mg/L). After puncture of the cyst, repeated ultrasound examination showed a decompression of the abdominal organs and a thick-walled folded membrane floating within the amniotic fluid in front of the ventral abdominal wall of the fetus (Figure 1B). The fetus showed classical features of the OEIS complex with a large infraumbilical anterior midline defect with a protruding omphalocele, (elephant-trunk appearance), bladder exstrophy below the omphalocele in an area of 3.7mm and sacral spina bifida as well as a singular umbilical artery. Consequently, the diagnosis of an OEIS complex with intact cloacal membrane was made. Two weeks later, a missed abortion was diagnosed and labor was induced. Postnatal visual examination of the fetus was performed and confirmed the diagnosis of OEIS.