Urorectal septum malformation sequence: Prenatal progression, clinical report, and embryology review

Abstract

The urorectal septum malformation sequence (URSMS) is characterized by severe abnormalities of the urorectal septum (URS) and urogenital organs. The primary defect in this condition appears to be a deficiency in caudal mesoderm leading to the malformation of the URS and other structures in the pelvic region. Recent clinical reports discuss prental findings of URSMS [Lubusky et al. (2006); Prenatal Diagnosis 26: 345-349]. However, here we present a case of URSMS with prenatal findings not previously described, review the literature on URSMS, and summarize current embryological understanding of the pathology seen in hindgut development. The unique prenatal finding in the patient was an abdominally located cystic mass that was first seen at 18 weeks of gestation. Over the next 6 weeks, the mass decreased in size until it disappeared. Concurrent with reduction of the cyst, ascites developed. The patient displayed several traditional URSMS indicators including abnormal bladder and dysplastic kidneys. Our findings give additional insight into the embryology of urorectogenital development. Specifically, they suggest that the cystic mass may have been a persistent urachus prior to septation of the cloaca. Postnatal evaluation confirmed a URSMS diagnosis; the newborn had ambiguous genitalia, hypoplastic kidneys, absent uterus, imperforate anus, smooth perineum, and overall underdeveloped urogenital structures.

Urorectal septum malformation sequence—Fetal series with the description of a new “intermediate” variant. Time to refine the terminology?

“…The authentic findings of these reported cases generally include a huge pelvic cyst without a normally shaped urinary bladder in situ. Other secondary findings may consist of ascites, enterolithiasis, oligohydramnios, and renal anomalies [Escobar et al, ]. In our series, all cases manifested with a huge and bizarre pelvic cyst which represented the persistent cloaca or urogenital sinus.…”

“…Previously, it was postulated that the URS first invades the primitive cloaca and fuses with the cloaca membrane, which thereafter breaks down into the openings of the urogenital membrane anteriorly and the anal membrane posteriorly [Wheeler et al, ]. Incomplete partition of the persistent cloaca by URS mesoderm (by 6th weeks) and failure to break down by the cloaca membrane (by 7th weeks) result in the full form of URSM [Escobar et al, ; Jain et al, ]. In contrast to the full form of URSM, the cloaca membrane in the partial form of URSM has ruptured, while partition of the cloaca was otherwise not completed [Wheeler and Weaver, ].…”

Umbilical cyst due to patent urachus in a fetus with complete urorectal septum malformation sequence

“…Escobar et al [1,13] have discussed the progression of URSM diagnosed prenatally and suggested the probability of deficiency of caudal mesoderm leading to malformation of urorectal septum and other pelvic organs. Though usually lethal, survival in a case with complete URSM who had moderate pulmonary hypoplasia and preserved left renal function was reported by Kanamori et al [14] after fetal vesico-amniotic shunting for a prominently dilated cloaca.…”

Survival in a Neonate with Complete Urorectal Septum Malformation Sequence after Fetal Vesico-Amniotic Shunting for a Prominently Dilated Cloaca

“…Also, reports of some URSMS patients born from diabetic mothers supported teratogenic or blastogenic factors as the etiology of URSMS [9] . Recently, Escobar et al [10] reported a URSMS case and discussed its etiology. Still, we should be careful in concluding whether the etiology of URSMS is exactly related to gene expression abnormalities caused by some teratogens or a gene mutation itself [11] .…”