Urorectal septum malformation sequence: Ultrasound correlation with fetal examination
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《美国医学杂志》
Department of Medical Genetics, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India
Abstract
Objectives : To correlate prenatal and postnatal findings of urorectal septum malformation sequence and to study spectrum of malformation. Methods : Nine cases were reviewed with features suggestive of urorectal septum malformation (URSM) sequence. Associated anomalies were studied. Sex of the fetus was assigned by karyotype when available or by examination of internal genitalia. Results : Out of nine cases 5 fetuses were male and 4 were female. Gestational age ranged from 14 to 34 weeks. Six cases were complete URSM sequence and 3 were partial URSM sequence. Associated anomalies of other systems were seen in 4 cases. In one case karyotype was 47, XXY. Conclusion : Cases with severe oligohydromnios with or without distended bladder, URSM sequence should be suspected, as this condition is usually lethal. Non-visualization of bladder, presence of hydronephrosis, multicystic kidneys or distended gut loops suggests the possibility of URSM sequence. The confirmation of diagnosis is possible after autopsy. Associated malformation of other organs and deformation due to oligohydromnios are commonly present.
Keywords: Urorectal septum malformation sequence; Lower mesodermal defects; Anal atresia; Ambiguous genitalia; Urethral agenesis, Hydronephrosis
Various structures of genitourinary system and lower part of gastrointestinal tract develop from the caudal end of mesoderm. Defective caudal end of mesoderm leads to a spectrum of malformations. Urorectal septum malformation (URSM) sequence is disorder of caudal end of mesoderm. The specific pattern of developmental anomalies of urogenital tracts and lower intestinal tract associated with lack of perineal openings and presence of ambiguous genitalia was named as 'urorectal malformation sequence' by Escobar et al (1987).[1] The name is based on the hypothesis that the cause of these septum malformations is failure of urorectal septum to fuse with cloacal membrane. The incidence of URSM sequence is one in 50,000-250,000 in neonates.[1],[2] Alternative names have been used like female pseudohermophroditism with caudal dysgenesis and cloacal dysgenesis sequence.[3],[4] Partial VSRM sequence and some of anorectal malformation represents milder form of complete VSRM.[5]
The cases not fulfilling strict diagnostic criteria of URSM sequence but with varying combinations of lower genitourinary and anal anomalies are grouped under partial URSM sequence[5] or lower mesodermal defects[6]. The complete URSM sequence is a lethal defect and leads to stillbirth or perinatal death.
Here is reported nine cases of urorectal septal malformations. Six of them satisfy the criteria of complete URSM sequence, and 3 cases can be labeled as partial URSM sequence.
Materials and Methods
Records of nine cases of urorectal septum malformation sequence were reviewed. These cases presented between the period of 1993-2003. Cases in which prenatal ultrasound was done, prenatal findings were noted. Photograph and radiograph were taken and detailed autopsy was done. Karyotype was done wherever possible either by prenatal or postnatal sampling. Sex of the fetus was assigned by karyotype when available or by examination of internal genitalia.
Results
The details of cases are given in table1. Out of 9 cases studied, 5 fetuses were male and 4 were female. Antenatal history did not reveal exposure to teratogen, infection or diabetes in any of the cases. There was no family history of similar disorder. Maternal age ranged from 23 to 33 years.
Gestational age of fetuses ranged from 14 weeks to 34 weeks. Seven fetuses were terminated after prenatal diagnosis of malformations, with poor prognosis. Out of the other two cases, one was stillborn (case 5) and the other was spontaneous abortion (case 7).
Prenatal ultrasonography (USG) findings were available in 7 cases. Five cases (case 1, 2, 3, 6 and 8) Figure1a,b,e,f had severe oligohydromnios. Out of these, 3 had distended urinary bladder (case 2, 6, 8) Figure1a, b and associated unilateral hydronephrosis in one case (case 2). In two cases, urinary bladder was not visualized and there was oligohydromnios. Out of them one had bilateral multicystic kidneys (case 3). The other case with non-visualization of bladder had distended bowel loops (case 1). Due to oligohydromnios, external genitalia could not be visualized during USG. In case 4, USG showed open spina bifida and omphalocele Figure1c. Genitourinary and gut anomalies were detected on autopsy Figure1d.
In one case, stillborn child had holoprosencephaly, congenital heart disease, polydactyly, and partial URSM sequence (case 5) was identified on autopsy. In case 7, URSM sequence was detected in a spontaneously aborted fetus. In cases 7 and 8, the mothers had earlier history of spontaneous abortion once and twice respectively.
Associated anomalies of other systems were seen in 4 cases, spinal rachisis and omphalocele in one; holoprosencephaly, preaxial polydactyly and ventricular septal defect in one; preaxial polydactyly and 2 vessel cord in one, and encephalocele in one. Potter facies and congenital talipoequinovarus (CTEV) due to oligohydromnios were seen in 3 cases. Isolated Potter facies and CTEV were detected in one case each. Two cases (case 2 and 8) had unilateral hypoplastic kidney. The other kidney had hydronephrosis, hydroureter (case 2) and multicystic dysplastic changes (case 8). In case 8, huge distended bladder folded on itself gave false impression of bilateral hydronephrosis on USG. On autopsy, right kidney was found to be normal in size and left kidney was hypoplastic Figure1e. No uterine abnormalities were seen. Lungs were hypoplastic in 5 cases (case 2, 3, 5, 6, and 9).
Six of the cases had no perineal openings and had a knob-like structure on the perineum Figure1f. None of them had median raphe. Three cases had normal external genitalia. Out of these three, two were females with imperforate anus and common cloaca and one male with imperforate anus and urethral obstruction. Karyotype was possible in four. In three cases (case 2, 5, 8), karyotype was normal and according to internal genitalia. In case 1 karyotype was 47, XXY.
Discussion
Between 5th-8th weeks of gestation, urorectal septum divides cloaca into anterior primitive urogenital sinus and posterior rectum. Failure to divide cloaca by urorectal septum and persistence of cloacal membrane lead to URSM sequence. Depending upon the severity of defect, spectrum of malformations has been described.
Six of the above cases fulfill the diagnostic criteria of complete URSM sequence - absence of perineal opening and ambiguous genitalia. Three had normal external genitalia. One of them had oligohydromnios and complete obstruction to urinary bladder. This can be labeled as partial URSM sequence severe type. Two other cases had single cloacal opening, and absent anal opening can be labeled as cloacal dysgenesis or partial URSM sequence. In these two cases, one had holoprosencephaly and the other had neural tube defect. Partial URSM sequence may be non-lethal.
After the first description of complete URSM sequence by Escobar, et al in 1987, till date 73 cases of complete URSM sequence are reported [3],[4],[7],[8]. Initially, this malformation was reported only in females; but the ratio of males to females in all cases reported is 0.87. In this small series there were 3 females and 6 males. The sex assignment is difficult due to ambiguity of external genitalia. Using absence of perineal opening and anal opening as selection criteria, Wheeler, et al (1997) described 13 cases and reviewed 49 cases from the literature. These cases can be labeled as complete URSM sequence. In all females there was absence of vaginal opening. Fused labia were present in 22% female cases. Phallus like structure was present in 72% females and was completely absent in 23% of males. Six of complete URSM sequence in our series had knob-like structure on the perineum and none of them had median raphe. Four of them were males and two were females. Wheeler and Weaver (2001) reviewed 25 cases of partial URSM sequence defined by persistent cloaca and single perineal/anal opening. Ambiguous genitalia were common in both the sexes. In the present three cases of partial URSM sequence, external genitalia were normal.
Secondary to oligohydromnios, features like Potter facies, TEV and pulmonary hypoplasia are common in these patients and were also present in 4/9, 4/9, 5/9 of our cases respectively
Renal dysplasia and agenesis is reported in 82% and 50% of cases respectively.[7] Dysplastic changes were seen in 3 of the present cases: bilateral in one case associated with non-visualization of bladder prenatally and unilateral in two. None of the cases had renal agenesis. Out of 4 females, one had vaginal atresia and in other two cases it was opening in the common cloaca.
The anomalies of other systems reported in association with URSM sequence are vertebral anomalies (56%), sacral agenesis or hypoplasia (47%), limb anomalies (25%), cardiac (16%), traecheoesophageal fistula in 18% and single umbilical artery (37%).[7] Radiograph of all of the cases was conducted and vertebrae were normal in all the cases except one who had spina bifida and myelomeningocele. Myelomeningocele is reported in one case of partial URSM sequence.[5] Single umbilical artery, preaxial-polydactyly present in each one of the present series has also been reported.
One of the present cases had holoprosencephaly, which is reported in association with caudal dysgenesis.[9] But association of holoprosencephaly with URSM sequence was not found in the literature. Omphalocele seen in one of our cases is reported only once in association with URSM sequence.[8]
Omphalocele is a part of OEIS complex. The other features of OEIS include exstrophy of cloaca, imperforate anus and spinal defects. Our case with omphalocele and the case reported by Seaver, et al 1994[4] also had spinal abnormalities, which highlight developmental commonalities between URSM sequence and OEIS complex. Various combinations of malformations of anogenital anomalies have also been reported under the name of lower mesodermal defects.[6]
Complete URSM sequence is associated with very poor prognosis, and survival is reported only in 4 cases out of 73 cases. Many of the cases are prenatally detected and terminated. Prenatal USG findings are obstruction to urinary bladder and oligohydromnios. It can be differentiated from posterior urethral valve by presence of large distended urinary bladder and absence of keyhole appearance due to distended urethra. It is rare that, urinary bladder may not be visualized due to associated agenesis of kidneys or dysplastic kidneys. Unilateral or bilateral hydronephrosis is a common finding. Though examination of external genitalia will be useful for diagnosis of URSM sequence, it is usually impossible to visualize due to severe oligohydromnios. Presence of distended gut loops and non-visualization of bladder in presence of oligohydromnios should alert one to the possibility of URSM sequence. Prenatal suspicion of this anomaly is essential as it is associated with lethality, and termination of pregnancy is likely to be an acceptable option
Though there are many theories explaining developmental origin of URSM sequence, there is no information about the etiology till date. One of our cases has karyotype of 47, XXY, but similar case has never been reported in the literature and the chromosomal anomaly may be coincidental. Seaver, et al (1994) reported absence of Y-specific DNA sequence in females with features of URSM sequence and ruled out the possibility of Y-specific sequences as pathogenic factor. One of their cases has deletion of part of q arm of chromosome 10. This region has a developmental gene, namely PAX2 gene, which was not found to be deleted or mutated in cases with female pseudohermaphroditism and caudal dysplasia.[4] PAX2 is unlikely to be a causative gene.
Animal studies done in mouse and chick embryo have shown URSM sequence defects after selective damage of lower end of mesoderm by ochratoxin A (fungal toxin) and etretinate (retinoic acid derivative).[10], [11] suggesting possibility of hidden teratogen yet to be identified.
Mild variety of URSM sequence is reported in mother and daughter indicating autosomal dominant inheritance.[12] But all other cases of severe forms of URSM sequence are sporadic; there is no risk of recurrence in the siblings.
Conclusion
URSM sequence should be suspected in prenatally- diagnosed cases of oligohydromnios with a distended bladder and renal malformations. Autopsy of such cases can provide confirmation of diagnosis. These cases also present as stillbirth and need to be distinguished from other causes of ambiguous genitalia.
References
1. Escobar LF, Weaver DD, Bixler D, Hodes ME, Mitchell M. Urorectal septum malformation sequence: report of six cases and embryological analysis. Am J Dis Child 1987; 141 : 1021-1024.
2. Blott M, Nicoladies KH, Gibb D, Greenough A, Moscoso G, Campbell S. Fetal breathing movements as predictor of favorable pregnancy outcome after oligohydromnios due to membrane rupture in second trimester. Lancet 1987; 2 :129-131.
3. Sahinoglu Z, Mulayim B, Ozden S, Etker S, Celayir A, Ozkan F Biligic R. The prenatal diagnosis of cloacal dysgenesis sequence in six cases: can the termination of pregnancy always be the first choice. Prenat Diagn 2004; 24 : 10-16.
4. Erickson RP, Stone JF, McNoe LA, Eccles MR. Molecular and clinical studies of three cases of female pseudohermaphroditism with caudal dysplasia suggest multiple etiologies. Clin Genet 1997; 51 : 331-337.
5. Wheeler PG, Weaver DD. Partial urorectal septum malformation sequence: A report of 25 cases. Am J Med Genet 2001; 103 : 99-105.
6. Pauli MR. Lower mesodermal defects: A common cause of fetal and early neonatal death. Am J Med Genet 1994; 50 : 154-172.
7. Wheeler PG, Weaver DD, Obeime MO, Vance GH, Bull MJ, Escobar LF. Urorectal septum malformation sequence: report of thirteen additional cases and review of the literature. Am J Med Genet 1997; 73 : 456-462.
8. Seaver LH, Grimes J, Erickson RP. Female pseudohermaphroditism with multiple caudal anomalies: Absence of Y-specific DNA sequences as pathogenetic factors. Am J Med Genet 1994; 51 : 16-21.
9. Martinez-Frias ML, Bermejo E, Garcia A, Galan E, Prieto L. Holoprosencephaly associated with caudal dysgenesis: A clinical-epidemiological analysis. Am J Med Genet 1994; 53 : 46-51.
10. Wei X, Sulik KK. Pathogenesis of caudal dysgenesis/sirenomelia induced by Ochratoxin A in chick embryos. Teratology 1996; 53 : 378-391.
11. Alles AJ, Sulik KK. A review of caudal dysgenesis and its pathogenesis as illustrated in an animal model. Birth defects Orig Artic Ser 1993; 29(1) : 83-102.
12. Mills PL, Pergament E. Urorectal septal defects in a female and her offspring. Am J Med Genet 1997; 70 : 250-252.(Patil SJ, Phadke Shubha R)
Abstract
Objectives : To correlate prenatal and postnatal findings of urorectal septum malformation sequence and to study spectrum of malformation. Methods : Nine cases were reviewed with features suggestive of urorectal septum malformation (URSM) sequence. Associated anomalies were studied. Sex of the fetus was assigned by karyotype when available or by examination of internal genitalia. Results : Out of nine cases 5 fetuses were male and 4 were female. Gestational age ranged from 14 to 34 weeks. Six cases were complete URSM sequence and 3 were partial URSM sequence. Associated anomalies of other systems were seen in 4 cases. In one case karyotype was 47, XXY. Conclusion : Cases with severe oligohydromnios with or without distended bladder, URSM sequence should be suspected, as this condition is usually lethal. Non-visualization of bladder, presence of hydronephrosis, multicystic kidneys or distended gut loops suggests the possibility of URSM sequence. The confirmation of diagnosis is possible after autopsy. Associated malformation of other organs and deformation due to oligohydromnios are commonly present.
Keywords: Urorectal septum malformation sequence; Lower mesodermal defects; Anal atresia; Ambiguous genitalia; Urethral agenesis, Hydronephrosis
Various structures of genitourinary system and lower part of gastrointestinal tract develop from the caudal end of mesoderm. Defective caudal end of mesoderm leads to a spectrum of malformations. Urorectal septum malformation (URSM) sequence is disorder of caudal end of mesoderm. The specific pattern of developmental anomalies of urogenital tracts and lower intestinal tract associated with lack of perineal openings and presence of ambiguous genitalia was named as 'urorectal malformation sequence' by Escobar et al (1987).[1] The name is based on the hypothesis that the cause of these septum malformations is failure of urorectal septum to fuse with cloacal membrane. The incidence of URSM sequence is one in 50,000-250,000 in neonates.[1],[2] Alternative names have been used like female pseudohermophroditism with caudal dysgenesis and cloacal dysgenesis sequence.[3],[4] Partial VSRM sequence and some of anorectal malformation represents milder form of complete VSRM.[5]
The cases not fulfilling strict diagnostic criteria of URSM sequence but with varying combinations of lower genitourinary and anal anomalies are grouped under partial URSM sequence[5] or lower mesodermal defects[6]. The complete URSM sequence is a lethal defect and leads to stillbirth or perinatal death.
Here is reported nine cases of urorectal septal malformations. Six of them satisfy the criteria of complete URSM sequence, and 3 cases can be labeled as partial URSM sequence.
Materials and Methods
Records of nine cases of urorectal septum malformation sequence were reviewed. These cases presented between the period of 1993-2003. Cases in which prenatal ultrasound was done, prenatal findings were noted. Photograph and radiograph were taken and detailed autopsy was done. Karyotype was done wherever possible either by prenatal or postnatal sampling. Sex of the fetus was assigned by karyotype when available or by examination of internal genitalia.
Results
The details of cases are given in table1. Out of 9 cases studied, 5 fetuses were male and 4 were female. Antenatal history did not reveal exposure to teratogen, infection or diabetes in any of the cases. There was no family history of similar disorder. Maternal age ranged from 23 to 33 years.
Gestational age of fetuses ranged from 14 weeks to 34 weeks. Seven fetuses were terminated after prenatal diagnosis of malformations, with poor prognosis. Out of the other two cases, one was stillborn (case 5) and the other was spontaneous abortion (case 7).
Prenatal ultrasonography (USG) findings were available in 7 cases. Five cases (case 1, 2, 3, 6 and 8) Figure1a,b,e,f had severe oligohydromnios. Out of these, 3 had distended urinary bladder (case 2, 6, 8) Figure1a, b and associated unilateral hydronephrosis in one case (case 2). In two cases, urinary bladder was not visualized and there was oligohydromnios. Out of them one had bilateral multicystic kidneys (case 3). The other case with non-visualization of bladder had distended bowel loops (case 1). Due to oligohydromnios, external genitalia could not be visualized during USG. In case 4, USG showed open spina bifida and omphalocele Figure1c. Genitourinary and gut anomalies were detected on autopsy Figure1d.
In one case, stillborn child had holoprosencephaly, congenital heart disease, polydactyly, and partial URSM sequence (case 5) was identified on autopsy. In case 7, URSM sequence was detected in a spontaneously aborted fetus. In cases 7 and 8, the mothers had earlier history of spontaneous abortion once and twice respectively.
Associated anomalies of other systems were seen in 4 cases, spinal rachisis and omphalocele in one; holoprosencephaly, preaxial polydactyly and ventricular septal defect in one; preaxial polydactyly and 2 vessel cord in one, and encephalocele in one. Potter facies and congenital talipoequinovarus (CTEV) due to oligohydromnios were seen in 3 cases. Isolated Potter facies and CTEV were detected in one case each. Two cases (case 2 and 8) had unilateral hypoplastic kidney. The other kidney had hydronephrosis, hydroureter (case 2) and multicystic dysplastic changes (case 8). In case 8, huge distended bladder folded on itself gave false impression of bilateral hydronephrosis on USG. On autopsy, right kidney was found to be normal in size and left kidney was hypoplastic Figure1e. No uterine abnormalities were seen. Lungs were hypoplastic in 5 cases (case 2, 3, 5, 6, and 9).
Six of the cases had no perineal openings and had a knob-like structure on the perineum Figure1f. None of them had median raphe. Three cases had normal external genitalia. Out of these three, two were females with imperforate anus and common cloaca and one male with imperforate anus and urethral obstruction. Karyotype was possible in four. In three cases (case 2, 5, 8), karyotype was normal and according to internal genitalia. In case 1 karyotype was 47, XXY.
Discussion
Between 5th-8th weeks of gestation, urorectal septum divides cloaca into anterior primitive urogenital sinus and posterior rectum. Failure to divide cloaca by urorectal septum and persistence of cloacal membrane lead to URSM sequence. Depending upon the severity of defect, spectrum of malformations has been described.
Six of the above cases fulfill the diagnostic criteria of complete URSM sequence - absence of perineal opening and ambiguous genitalia. Three had normal external genitalia. One of them had oligohydromnios and complete obstruction to urinary bladder. This can be labeled as partial URSM sequence severe type. Two other cases had single cloacal opening, and absent anal opening can be labeled as cloacal dysgenesis or partial URSM sequence. In these two cases, one had holoprosencephaly and the other had neural tube defect. Partial URSM sequence may be non-lethal.
After the first description of complete URSM sequence by Escobar, et al in 1987, till date 73 cases of complete URSM sequence are reported [3],[4],[7],[8]. Initially, this malformation was reported only in females; but the ratio of males to females in all cases reported is 0.87. In this small series there were 3 females and 6 males. The sex assignment is difficult due to ambiguity of external genitalia. Using absence of perineal opening and anal opening as selection criteria, Wheeler, et al (1997) described 13 cases and reviewed 49 cases from the literature. These cases can be labeled as complete URSM sequence. In all females there was absence of vaginal opening. Fused labia were present in 22% female cases. Phallus like structure was present in 72% females and was completely absent in 23% of males. Six of complete URSM sequence in our series had knob-like structure on the perineum and none of them had median raphe. Four of them were males and two were females. Wheeler and Weaver (2001) reviewed 25 cases of partial URSM sequence defined by persistent cloaca and single perineal/anal opening. Ambiguous genitalia were common in both the sexes. In the present three cases of partial URSM sequence, external genitalia were normal.
Secondary to oligohydromnios, features like Potter facies, TEV and pulmonary hypoplasia are common in these patients and were also present in 4/9, 4/9, 5/9 of our cases respectively
Renal dysplasia and agenesis is reported in 82% and 50% of cases respectively.[7] Dysplastic changes were seen in 3 of the present cases: bilateral in one case associated with non-visualization of bladder prenatally and unilateral in two. None of the cases had renal agenesis. Out of 4 females, one had vaginal atresia and in other two cases it was opening in the common cloaca.
The anomalies of other systems reported in association with URSM sequence are vertebral anomalies (56%), sacral agenesis or hypoplasia (47%), limb anomalies (25%), cardiac (16%), traecheoesophageal fistula in 18% and single umbilical artery (37%).[7] Radiograph of all of the cases was conducted and vertebrae were normal in all the cases except one who had spina bifida and myelomeningocele. Myelomeningocele is reported in one case of partial URSM sequence.[5] Single umbilical artery, preaxial-polydactyly present in each one of the present series has also been reported.
One of the present cases had holoprosencephaly, which is reported in association with caudal dysgenesis.[9] But association of holoprosencephaly with URSM sequence was not found in the literature. Omphalocele seen in one of our cases is reported only once in association with URSM sequence.[8]
Omphalocele is a part of OEIS complex. The other features of OEIS include exstrophy of cloaca, imperforate anus and spinal defects. Our case with omphalocele and the case reported by Seaver, et al 1994[4] also had spinal abnormalities, which highlight developmental commonalities between URSM sequence and OEIS complex. Various combinations of malformations of anogenital anomalies have also been reported under the name of lower mesodermal defects.[6]
Complete URSM sequence is associated with very poor prognosis, and survival is reported only in 4 cases out of 73 cases. Many of the cases are prenatally detected and terminated. Prenatal USG findings are obstruction to urinary bladder and oligohydromnios. It can be differentiated from posterior urethral valve by presence of large distended urinary bladder and absence of keyhole appearance due to distended urethra. It is rare that, urinary bladder may not be visualized due to associated agenesis of kidneys or dysplastic kidneys. Unilateral or bilateral hydronephrosis is a common finding. Though examination of external genitalia will be useful for diagnosis of URSM sequence, it is usually impossible to visualize due to severe oligohydromnios. Presence of distended gut loops and non-visualization of bladder in presence of oligohydromnios should alert one to the possibility of URSM sequence. Prenatal suspicion of this anomaly is essential as it is associated with lethality, and termination of pregnancy is likely to be an acceptable option
Though there are many theories explaining developmental origin of URSM sequence, there is no information about the etiology till date. One of our cases has karyotype of 47, XXY, but similar case has never been reported in the literature and the chromosomal anomaly may be coincidental. Seaver, et al (1994) reported absence of Y-specific DNA sequence in females with features of URSM sequence and ruled out the possibility of Y-specific sequences as pathogenic factor. One of their cases has deletion of part of q arm of chromosome 10. This region has a developmental gene, namely PAX2 gene, which was not found to be deleted or mutated in cases with female pseudohermaphroditism and caudal dysplasia.[4] PAX2 is unlikely to be a causative gene.
Animal studies done in mouse and chick embryo have shown URSM sequence defects after selective damage of lower end of mesoderm by ochratoxin A (fungal toxin) and etretinate (retinoic acid derivative).[10], [11] suggesting possibility of hidden teratogen yet to be identified.
Mild variety of URSM sequence is reported in mother and daughter indicating autosomal dominant inheritance.[12] But all other cases of severe forms of URSM sequence are sporadic; there is no risk of recurrence in the siblings.
Conclusion
URSM sequence should be suspected in prenatally- diagnosed cases of oligohydromnios with a distended bladder and renal malformations. Autopsy of such cases can provide confirmation of diagnosis. These cases also present as stillbirth and need to be distinguished from other causes of ambiguous genitalia.
References
1. Escobar LF, Weaver DD, Bixler D, Hodes ME, Mitchell M. Urorectal septum malformation sequence: report of six cases and embryological analysis. Am J Dis Child 1987; 141 : 1021-1024.
2. Blott M, Nicoladies KH, Gibb D, Greenough A, Moscoso G, Campbell S. Fetal breathing movements as predictor of favorable pregnancy outcome after oligohydromnios due to membrane rupture in second trimester. Lancet 1987; 2 :129-131.
3. Sahinoglu Z, Mulayim B, Ozden S, Etker S, Celayir A, Ozkan F Biligic R. The prenatal diagnosis of cloacal dysgenesis sequence in six cases: can the termination of pregnancy always be the first choice. Prenat Diagn 2004; 24 : 10-16.
4. Erickson RP, Stone JF, McNoe LA, Eccles MR. Molecular and clinical studies of three cases of female pseudohermaphroditism with caudal dysplasia suggest multiple etiologies. Clin Genet 1997; 51 : 331-337.
5. Wheeler PG, Weaver DD. Partial urorectal septum malformation sequence: A report of 25 cases. Am J Med Genet 2001; 103 : 99-105.
6. Pauli MR. Lower mesodermal defects: A common cause of fetal and early neonatal death. Am J Med Genet 1994; 50 : 154-172.
7. Wheeler PG, Weaver DD, Obeime MO, Vance GH, Bull MJ, Escobar LF. Urorectal septum malformation sequence: report of thirteen additional cases and review of the literature. Am J Med Genet 1997; 73 : 456-462.
8. Seaver LH, Grimes J, Erickson RP. Female pseudohermaphroditism with multiple caudal anomalies: Absence of Y-specific DNA sequences as pathogenetic factors. Am J Med Genet 1994; 51 : 16-21.
9. Martinez-Frias ML, Bermejo E, Garcia A, Galan E, Prieto L. Holoprosencephaly associated with caudal dysgenesis: A clinical-epidemiological analysis. Am J Med Genet 1994; 53 : 46-51.
10. Wei X, Sulik KK. Pathogenesis of caudal dysgenesis/sirenomelia induced by Ochratoxin A in chick embryos. Teratology 1996; 53 : 378-391.
11. Alles AJ, Sulik KK. A review of caudal dysgenesis and its pathogenesis as illustrated in an animal model. Birth defects Orig Artic Ser 1993; 29(1) : 83-102.
12. Mills PL, Pergament E. Urorectal septal defects in a female and her offspring. Am J Med Genet 1997; 70 : 250-252.(Patil SJ, Phadke Shubha R)