Severe Anorectal Malformations Research Articles

Challenges in the Prenatal Diagnosis of Cloaca.

Background:Cloaca is a common excretory channel for the genital, urinary, and gastrointestinal tracts. It is considered a severe anorectal malformation caused by failed partitioning of the genital, rectal, and urinary tracts.Methods:We report 5 infants with cloaca at birth who were identified prenatally by one or more of the following on prenatal ultrasound (US): ambiguous genitalia, a cystic pelvic/abdominal mass, hydronephrosis, ascites, a single umbilical artery, and oligohydramnios.Results:A cystic pelvic/abdominal mass and ambiguous genitalia were each observed in 3 cases by prenatal US. Ambiguous genitalia was observed in all 5 neonates at birth. There were 2 twin pregnancies (dichorionic/diamniotic and monochorionic/monoamniotic), with only 1 twin in a set affected with cloaca.Conclusion:Pediatricians should be alert to the prenatal US findings that may raise suspicion of a persistent cloaca to improve both prenatal counseling and family preparation.

Defining the molecular pathologies in cloaca malformation: similarities between mouse and human

Anorectal malformations are congenital anomalies that form a spectrum of disorders, from the most benign type with excellent functional prognosis, to very complex, such as cloaca malformation in females in which the rectum, vagina and urethra fail to develop separately and instead drain via a single common channel into the perineum. The severity of this phenotype suggests that the defect occurs in the early stages of embryonic development of the organs derived from the cloaca. Owing to the inability to directly investigate human embryonic cloaca development, current research has relied on the use of mouse models of anorectal malformations. However, even studies of mouse embryos lack analysis of the earliest stages of cloaca patterning and morphogenesis. Here we compared human and mouse cloaca development and retrospectively identified that early mis-patterning of the embryonic cloaca might underlie the most severe forms of anorectal malformation in humans. In mouse, we identified that defective sonic hedgehog (Shh) signaling results in early dorsal-ventral epithelial abnormalities prior to the reported defects in septation. This is manifested by the absence of Sox2 and aberrant expression of keratins in the embryonic cloaca of Shh knockout mice. Shh knockout embryos additionally develop a hypervascular stroma, which is defective in BMP signaling. These epithelial and stromal defects persist later, creating an indeterminate epithelium with molecular alterations in the common channel. We then used these animals to perform a broad comparison with patients with mild-to-severe forms of anorectal malformations including cloaca malformation. We found striking parallels with the Shh mouse model, including nearly identical defective molecular identity of the epithelium and surrounding stroma. Our work strongly suggests that early embryonic cloacal epithelial differentiation defects might be the underlying cause of severe forms of anorectal malformations in humans. Moreover, deranged Shh and BMP signaling is correlated with severe anorectal malformations in both mouse and humans.

Genotype–phenotype correlation in four 15q24 deleted patients identified by array‐CGH

Microdeletion 15q24 is an emerging syndrome recently described, mainly due to increased use of array-CGH. Clinical features associate mild to moderate developmental delay, typical facial characteristics (high forehead and frontal hairline, broad eyebrows, downslanting palpebral features, long philtrum), hands (particularly proximal implanted thumbs) and genital anomalies (micropenis, hypospadias). We report here on four de novo cases having 2.5-6.1 Mb deletions involving 15q24: one 15q23q24.2 (Patient 1) and three 15q24.1q24.2 deletions (Patients 2-4). We correlate phenotype to genotype according to molecular boundaries of these deletions. Since bilateral iris coloboma and severe ano-rectal malformation were only present in Patient 1, we could link these anomalies to haploinsufficiency of 15q23 genes. Neither hypospadias nor micropenis were present in Patient 3 bearing the smallest deletion, therefore we could define 500 kb 15q24.1 region linked to these anomalies.

Bidirectional signaling mediated by ephrin-B2 and EphB2 controls urorectal development

Incomplete urethral tubularization (hypospadias) and anorectal abnormalities are two common and poorly understood birth defects that affect the extreme caudal midline of the human embryo. We now show that cell surface molecules essential for proper axon pathfinding in the developing nervous system, namely ephrin-B2 and the ephrin receptors EphB2 and EphB3, also play major roles in cell adhesion events that tubularize the urethra and partition the urinary and alimentary tracts. Mice carrying mutations which disrupt the bidirectional signals that these molecules transduce develop with variably penetrant severe hypospadias and incomplete midline fusion of the primitive cloaca. We further show that animals completely lacking ephrin-B2 reverse signaling present a fully penetrant failure in cloacal septation. This results in severe anorectal malformations characterized by an absence of the terminal-most hindgut (rectum) and formation of a fistula that aberrantly connects the intestines to the urethra at the base of the bladder. Consistent with an apparent requisite for both forward and reverse signaling in these caudal remodeling events, EphB2 and ephrin-B2 are coexpressed at the midline in the fusing urethral/cloacal endoderm and underlying lateral mesoderm of the urorectal septum that migrates toward the caudal midline as the cloaca septates. Our data thus indicate that B-subclass Eph and ephrin molecules play an important role in these clinically significant midline cell–cell adhesion and fusion events.

The results of pelvic muscle biofeedback exercise in children with faecal incontinence after surgery for severe anorectal malformation

Purpose: Children with severe anorectal malformation, after anorectoplasty, frequently have faecal soiling, which is disruptive functionally and psychosocially. Post‐operative bowel management program involves multimodality treatment including drug manipulation, laxative enema and pelvic muscle training. The results of pelvic muscle biofeedback exercise are reviewed.Methods: Patients with anorectal malformation after anorectoplasty were followed‐up at continence clinic with symptom scoring (Rintala score). Co‐operative patients with problematic soiling were selected for biofeedback treatment program. Pelvic musculature anatomy and physiology were assessed by anorectal manometry, magnetic‐ resonance imaging and transrectal ultrasonography. They received active pelvic musculature stimulation and biofeedback training of pelvic muscle (Myoexorciser 1000 Biofeedback System – VERIMED, Florida, USA). Duration of treatment ranged from 3 to 6 months. Outcome was measured by incontinence score, manometry and electromyogram of pelvic muscle.Results: Eight boys, aged 5–11 years, completed the biofeedback program. Soiling frequency dropped significantly post treatment (P=0.0431). Electromyogram of pelvic muscle improved (P < 0.05). Overall symptom‐score confirmed functional improvement.Conclusions: Biofeedback training program benefits children with intractable soiling after surgery for severe anorectal malformation. Follow up studies are required to confirm whether the benefit is sustained in the long term.

Deletion of fibroblast growth factor receptor 2b (Fgfr2b) gene results in anorectal malformation in mouse

Introduction: Anorectal malformations occur in 1 per 4,000 live births, and represent a surgical challenge. Fgfr2b is known to serve a key role in the development of other organ systems including parts of the gastrointestinal tract (GIT). We sought to evaluate the role of Fgfr2b in the development of normal anorectal structures. Methods:Fgfr2b expression in wild type (Wt) embryos was evaluated using whole mount in-situ hybridization. Wt and Fgfr2b-/- embryos were harvested from timed pregnant mothers at E10.5 through E18.5 and were analyzed for anorectal phenotype. Results: FGFR2 is expressed throughout the structures of the hindgut (data not shown). Fgfr2b-/- mutants demonstrate a genetically reproducible severe anorectal malformation, characterized by a shortened perineal body, an absence of pelvic rectum, and no visible distal recto-urinary fistula as shown in figure. Figure: E18.5 landscape view of perineum in Wt (a) and Fgfr2b-/- (b), transected tail (T), anus (A), genital tubercle (GT); Sagittal section of pelvis in Wt (c) and Fgfr2b-/- (d) bladder (B) urethra (U), genital tubercle (GT), rectum (R) and Anus (A). Conclusions: FGFR2 is expressed early in distal hindgut indicating an active role in development of normal anorectal continuity. Furthermore, Fgfr2b invalidation (Fgfr2b-/- mutant), results in a severe anorectal malformation as demonstrated in both landscape and cross sectional views. Fgfr2b function is required for development of anorectal continuity. Further mechanistic investigation of Fgfr2b in hindgut and anus interactions may lead to a better understanding of the mechanism of development these anomalies in humans.