Anatomical basis of a common embryological origin for epispadias and bladder or cloacal exstrophies

Exstrophy-Epispadias Complex

Exstrophy-epispadias complex encompasses a spectrum of disorders with lower abdominal midline malformations, including epispadias, bladder exstrophy, and cloacal exstrophy, also known as Omphalocele-Exstrophy-Imperforate Anus-Spinal Anomalies Complex. In this review, the authors discuss the epidemiology, embryologic cause, prenatal findings, phenotypic characteristics, and management strategies of these 3 conditions. The primary focus is to summarize outcomes pertaining to each condition.

Role of the Pubic Symphysis in Osseous Pelvic Development: A Novel Model of Bladder Exstrophy in Rabbits

BACKGROUND

It has been posited that the osseous pelvic anomalies seen in patients with classic bladder exstrophy (CBE) result from disruption of the pubic symphysis. This hypothesis, however, has not been tested. In the present animal study, our objective was to determine whether the tension of the pubic symphysis helps maintain the shape of the pelvic ring, or whether the growing bones maintain a ring shape even without the tension of the symphysis.

METHODS

In total, 12 neonatal New Zealand White rabbits underwent pubic symphysiotomy (experimental group, n=9) or sham surgery (control group, n=3) on days 3 or 4 of life. Rabbits were scanned with cone-beam computed tomography at 1, 4, 12, and 20 weeks postoperatively to monitor changes in the following pelvic parameters, which are known to be altered in CBE: anterior segment angle, anterior segment length, intertriradiate distance, interpubic distance, and posterior segment angle. Changes within the experimental and control groups were evaluated using repeated-measures analysis of variance and post hoc Tukey honest significant difference testing. Two-tailed t tests were used to compare treatment groups at each time point.

RESULTS

Both groups showed increases in anterior segment length and intertriradiate distance during the study period; rabbits in the experimental group also showed a steady increase in interpubic distance (F=43.9; P<0.001). Experimental rabbits had significantly larger mean values for anterior segment angle, intertriradiate distance, interpubic distance, and posterior segment angle than did control rabbits at all time points. We found no difference in mean anterior segment length between control and experimental groups at any time point. The difference in interpubic distance was particularly pronounced by 20 weeks (experimental group, 13±2.7 mm; control group, 1.1±0.1 mm; P<0.001).

CONCLUSIONS

The pubic symphysis is essential for normal pelvic development. Its absence led to early pelvic angulation and progressive pubic separation in a rabbit model. However, we found no significant difference in the mean anterior segment length, and it is likely that other factors are also implicated in the growth disturbance seen in CBE.

LEVEL OF EVIDENCE

Level V.

Pathogenesis of bladder exstrophy: A new hypothesis

Classical bladder exstrophy affects 1 in 30 000 live births. Results of surgical treatment from different institutions employing various surgical techniques are not uniform, thus there is a need for a consensus on the best technique for bladder exstrophy repair. Surgical correction in bladder exstrophy would be more effective if the exact pathogenetic mechanism was deduced and the procedure was directed to correct the cause, which is responsible for the defect. The anatomy of exstrophy shows that the infraumbilical abdominal wall, the anterior wall of the bladder, and the urethra are split, with splayed out genitalia and musculature along with pubic diastasis. There is no tissue loss and hence embryological defect is unlikely to be the cause of bladder exstrophy. Thus there is a need to examine pathogenesis of bladder exstrophy.

METHODS

A literature search was made of the various hypotheses for cause of bladder exstrophy, and attempts were made to propose a new hypothesis. The present hypothesis is also the basis for a technique of mobilization of pelvic musculature, done in two stages.

RESULTS

The functional outcomes of 38 children with bladder exstrophy managed over a period of 10 years were reviewed. At a mean follow-up of 4.5 years (range 2.5-8 years), 82% of patients were functionally continent.

CONCLUSIONS

The exact embryopathogenesis of bladder exstrophy is unknown. In this study a new hypothesis is proposed, with the aim of tailoring the surgical procedure to correct this defect. Bladder exstrophy epispadias complex (BEEC) is a deformative disruption occurring after embryogenic phase and pubic diastasis, and is central to exstrophy development. A working hypothesis can be formulated in line with our observation so that future experiments based this new hypothesis can aim to elucidate the exact pathogenesis.

Cloacal exstrophy: an epidemiologic study from the International Clearinghouse for Birth Defects Surveillance and Research

Cloacal exstrophy presents as a complex abdominal wall defect thought to result from a mesodermal abnormality. Anatomically, its main components are Omphalocele, bladder Exstrophy and Imperforate anus. Other associated malformations include renal malformations and Spine defects (OEIS complex). Historically, the prevalence ranges from 1 in 200,000 to 400,000 births, with higher rates in females. Cloacal exstrophy is likely etiologically heterogeneous as suggested by its recurrence in families and occurrence in monozygotic twins. The defect has been described in infants with limb-body wall, with trisomy 18, and in one pregnancy exposed to Dilantin and diazepam. Due to its rarity, the use of a nonspecific diagnostic code for case identification, and lack of validation of the clinical findings, cloacal exstrophy remains an epidemiologic challenge. The purpose of this study was to describe the prevalence, associated anomalies and maternal characteristics among infants born with cloacal exstrophy. We used data from the International Clearinghouse for Birth Defects Surveillance and Research submitted from 18 birth defect surveillance programs representing 24 countries. Cases were clinically evaluated locally and reviewed centrally by two authors. Cases of persistent cloaca were excluded. A total of 186 cases of cloacal exstrophy were identified. Overall prevalence was 1 in 131,579 births: ranging from 1 in 44,444 births in Wales to 1 in 269,464 births in South America. Live birth prevalence was 1 in 184,195 births. Prevalence ratios did not vary by maternal age. Forty-two (22.6%) cases met the criteria for the OEIS complex, whereas 60 (32.3%) were classified as OEI and 18 (9.7%) as EIS (one with suspected VATER (0.5%)). Other findings included two cases with trisomy 13 (one without a karyotype confirmation), one with mosaic trisomy 12 (0.5%), one with mosaic 45,X (0.5%) and one classified as having amnion band sequence (0.5%). Twenty-seven (14.5%) infants had other anomalies unrelated to cloacal exstrophy. Cloacal exstrophy is a rare anomaly with variability in prevalence by geographic location. The proportion of cases classified as OEIS complex was lower in this study than previously reported. Among all cases, 54.8% were reported to have an omphalocele.

Common ("classical") and covered cloacal exstrophy: a histopathological study and a reconstruction of the pathogenesis

Current opinion about structure and pathogenesis of cloacal exstrophy was challenged by histopathological findings and new insights into the normal development. Autopsy specimens of common (n = 3) and covered cloacal exstrophy (n = 4) with single intraexstrophic and -perineal phallic structures and perineo-exstrophic canals have been analyzed histopathologically. The findings were correlated to normal development to reconstruct the pathogenesis. By identifying a specific cloaca-derived urethra field as distinct from allantois-derived bladder fields, the exstrophic area is found to reflect the original hindgut configuration in embryos of approximately 26-29 postovulatory days gestational age (2-4 mm). Correlation to normal development suggests malfunctioning of the primitive streak/caudal eminence as a primary fault that leads to a defective cloacal region in the hindgut disturbing cloacal-intestinal-allantoic dissociation and also causes lengthening of the intestinal region into a blind-ending colon, teratoma-like lesions, and vertebral and muscular anomalies. The current idea that membranes in "covered cloacal exstrophy" represent persisting cloacal membranes is dismissed by finding an amnion-like structure, which suggests dysfunction of an umbilical ring placode as a simultaneous 2nd fault. This malfunctioning may cause omphalocele by defective demarcation of the umbilical cord and may replace midline stroma of the infraumbilical abdominal wall by extraembryonic tissue that stretches into a weak temporary membrane, may leave a perineo-extrophic canal, and may allow the formation of a single perineal or intraexstrophic phallus. Malfunctioning without replacement may result in a purely epithelial "allantoic" membrane, which by disintegrating in combination with the cloacal membrane will expose common cloacal exstrophy.

Embryogenesis of bladder exstrophy: A new hypothesis

AIMS AND OBJECTIVE

To postulate a hypothesis to explain the embryogenesis of exstrophy bladder based on our clinical observations.

MATERIALS AND METHODS

In 27 cases of exstrophy, we measured the distance between the lowermost inguinal skin crease to the root of the penis (clitoris) (B) and the distance between the penis (clitoris) and the scrotum (labia majora) (C). These were compared with age, height and XP distance (distance between xiphisternum and symphysis pubis) matched control group of normal children. The distance between the lowermost inguinal skin crease and the penis (clitoris) (A) was measured in control group.

RESULTS

The observation was A = B + C. This implies that in exstrophy bladder, the position of the penis (clitoris) has moved cephalad from the lower border of A to the junction of B and C.

CONCLUSION

Based on the observations, we postulate that abnormal origin of genital tubercle may be the cause of exstrophy bladder. The abnormal origin of primordia of the genital tubercle in more cephalad direction than normal causes wedge effect, which will interfere with the medial migration of the mesoderm as well as the midline approximation of mesodermal structures in the lower abdominal wall, thereby resulting in the exstrophy of bladder.

Seven new cases of familial isolated bladder exstrophy and epispadias complex (BEEC) and review of the literature

Clustering of the bladder exstrophy and epispadias complex (BEEC) has been described in 29 families. To explore the genetic contribution we located new families through the German and Austrian Bladder Exstrophy Support Group and the Association for the Bladder Exstrophy Community (predominantly US and Canada). We report six new families with two occurrences of BEEC, one family where the proband is the product of a consanguineous union, and four discordant twin pairs. In conjunction with the published clinical and epidemiological reports this collection suggests that there is a significant genetic predisposition for susceptibility to the BEEC. It also highlights the importance of self-referral groups for recruiting families for multicenter collaborative research efforts to identify susceptibility loci.