Maternal history

A 31-year-old G4P3003 was referred for evaluation due to the finding of an omphalocele by routine second trimester screening ultrasound. The pregnancy course had been uncomplicated up to this point, including normal prenatal labs. Serum screening had been declined by the patient. Her obstetric history is significant for three full-term vaginal deliveries without complication. The remainder of her history and the family history is unremarkable. No environmental exposures were elicited.

Evaluation

Comprehensive evaluation performed at 25-weeks gestation included detailed ultrasound, echocardiography and ultra rapid fetal MRI. Biometrics were appropriate for gestational age. A large omphalocele containing liver, gallbladder and bowel was seen. Gender could not be determined as the finding in the ultrasound image distorted the visualization between the fetal legs. The pubic bones were splayed and no bladder could be identified. Further imaging of the fetal spine was seen in the MRI demonstrating a neural tube defect. The left kidney could not be visualized and amniotic fluid was normal. A two-vessel umbilical cord was noted. Fetal echocardiogram was normal.

Pregnancy and delivery course

The patient had routine prenatal course. The baby was delivered by cesarean at 36-weeks gestation after presenting with spontaneous labor. The neonate was vigorous at delivery with normal cord gases and weighed 2.6 kg. Neonatology was present for the delivery to stabilize the patient. Gender could not be determined at delivery and the neonate was admitted to the newborn intensive care nursery for ongoing care.

Questions

1. Based on the constellation of findings, what is the likely diagnosis?
2. What is the significance of the ultrasound finding?
3. What are associated anomalies seen with this disorder?
4. Is a karyotype indicated in this situation?
5. How do you counsel the parents regarding recurrence risk?
6. What is the long-term prognosis for these children? 

Read on below for the answers.

Answers

1. OEIS sequence: Omphalocele, exstrophy of the cloaca, imperforate anus and spinal defects.
2. The finding is the classic appearance of the “elephant’s trunk” in which the terminal ileum prolapses through the cecum and is often seen between the fetal legs. This can also further obscure gender determination.
3. Single umbilical artery, limb defects (arthrogryposis, club feet, syndactyly), cardiac, gastrointestinal (atresia, malrotation, bowel duplication), neurologic (hydrocephalus) and urogenital (renal agenesis, ectopic kidney, duplicated collecting system, ambiguous genitalia, abnormal scrotum, uterine abnormalities) anomalies have been described.
4. Yes. It is often difficult to determine phenotypic gender based on physical exam and imaging studies due to the wide range of urogenital anomalies. Peripheral blood karyotype to determine genotypic sex is indicated. In addition, although the overwhelming majority of cases of OEIS sequence are associated with a normal karyotype, abnormal karyotypes have been reported.
5. OEIS sequence is thought to be sporadic. However, it has been reported in association with chromosome abnormalities. Discordance for OEIS has been reported in monochorionic and dichorionic twins. It has been postulated that there is an increased incidence in pregnancies conceived by IVF. Familial cases of similar anomalies have also been reported, suggesting a possible genetic component. There has been no definitive gene found to be associated with OEIS sequence. The abnormality is thought to be due to a failure of migration of caudal mesenchyme that creates the infraumbilical abdominal wall and urorectal septum resulting in a persistent cloaca with an imperforate anus. This then leads to the exstrophy of the cloaca and the incomplete mesenchymal development also involves malformations of the somites of the spine resulting in spinal defects. Homeobox genes and the retinoic acid pathway have been thought to be candidate genes for investigation.
6. Most individuals with OEIS sequence have a normal karyotype and normal neurodevelopmental outcomes. Care for these children is optimized in a multidisciplinary team setting. These children are at risk for significant morbidity and require multiple corrective surgeries, including the genitourinary and gastrointestinal systems. Attempts are largely made to keep phenotypic gender consistent with genotypic gender. These children will frequently require lifelong colostomy or ileostomy, as well as intermittent catheterization. Renal malformations and recurrent urinary tract infections can lead to renal dysfunction. Sexual function and fertility are likely to be reduced or absent. Ambulation is typically dependent upon the level of the spinal lesion and stability of the pelvis. Psychosocial support for the patient and the family is necessary particularly during the teen and early adult years.

References

• Tiblad E, Wilson RD, Carr M, Flake AW, Hedrick H, Johnson MP, Bebbington MW, Mann S, Adzick NS. OEIS sequence – a rare congenital anomaly with prenatal evaluation and postnatal outcome in six cases. Prenat Diagn 2008;28:141-147.
• Keppler-Noreuil KM. OEIS Complex (Omphalocele-Exstrophy-Imperforate Anus-Spinal Defects): A review of 14 cases. Am J Med Genet 2001;99:271-279.