EPISPADIAS
EXSTROPHY COMPLEX
The exstrophy-epispadias complex encompasses a
spectrum of disorders thought to represent increasingly severe defects in
infraumbilical midline development. There is invariable involvement of the
urinary tract and genitalia, and there may also be involvement of the abdominal
wall, anus, pelvis, and spine. The timing and nature of the underlying
embryologic defect are thought to determine which structures are involved, and
thus which condition in the complex will result. In order of increasing
severity and multisystem involvement, the conditions in the complex are known
as epispadias, bladder exstrophy, and cloacal exstrophy.
Classification
Epispadias, the least severe
condition, features an open defect in the dorsal wall of the urethra. As a
result, the urethra becomes a flat strip of exposed mucosa. In males, this strip
begins at the external meatus and continues proximally either to the base of
the glans (balanic epispadias), base of the penis (penile epispadias), or
bladder neck (penopubic epispadias). In penopubic epispadias, the defect
usually leads to absence of the normal sphincter mechanisms, resulting in
urinary incontinence. In females, the dorsal urethral defect may likewise be
short, resulting in a patulous urethral orifice, or more extensive, causing an
open defect that reaches the neck of the bladder.
Bladder exstrophy is a more
severe condition in which there is failed closure of the anterior abdominal
wall in the midline. In addition, there are multiple abnormalities of the bony
pelvis, including a wide pubic diastasis. The umbilicus is low set and marks
the cranial extent of the abdominal wall defect, whereas the anus is anteriorly
displaced and marks the caudal end of the defect. The anterior wall of the
bladder is absent, and the everted posterior wall of the bladder is exposed
through the abdominal wall defect. The ureteric orifices are visible and
laterally displaced, with shortened intramural segments. Epispadias is always
present. Males have a foreshortened penis, which reflects both a reduction in
anterior corpora cavernosal tissue, as well as retraction of cavernosal tissue
secondary to the pubic diastasis. Females have a bifid clitoris and
foreshortened vagina. Umbilical and indirect inguinal hernias are often
present.
Cloacal exstrophy is the most
severe condition in which bladder exstrophy is accompanied by bladder division,
exstrophy of the terminal ileum between the two halves of the bladder, a
blind-ended hindgut, imperforate anus, omphalocele, complete phallic division
(in males), complete vaginal and uterine duplication (in females), and spinal
defects.
Bladder exstrophy is the most
common of these three anomalies. The incidence is reported to be between 2.1
and 4 per 100,000 births, although it has been declining, likely due to
prenatal diagnosis and termination of affected fetuses. There is at least a 2 :
1 male-to-female ratio, with some series reporting an even higher male
predilection. Isolated epispadias occurs in approximately 1 in 117,000 males
and 1 in 484,000 females. Finally, cloacal exstrophy occurs in 1 in 200,000 to
1 in 400,000 births.
Pathogenesis
The embryologic defect
underlying the epispadiasexstrophy complex is poorly understood. The most
prominent theory argues that the main defect lies in the cloacal membrane, the
bilaminar structure consisting of ectoderm and endoderm that is situated
anterior to the cloaca (see Plate 2-3). In normal development, the cloacal
membrane occupies a large territory on the ventral surface of the embryo just
inferior to the body stalk. As development proceeds, however, mesoderm invades
the cranial aspect of the cloacal membrane, interposing itself between the
ectoderm and endoderm. This mesoderm, which now occupies the infraumbilical
space, fuses in the midline and gives rise to the infraumbilical abdominal
wall, pubic rami, and anterior surface of the detrusor muscle. In addition,
specialized regions of the mesoderm form the paired genital folds, which fuse
in the midline to form the genital tubercle (see top left illustration
in Plate 2-4). In the meantime, the cloaca undergoes septation into an anterior
urogenital sinus and posterior rectum, the orifices of which become exposed
following apoptosis of the cloacal membrane.
If the cloacal membrane does not
permit mesodermal invasion, midline fusion of the mesodermal structures is not
possible, resulting in midline defects of the abdominal wall and pelvis. In
cloacal exstrophy, this defect is hypothesized to occur in conjunction with
abnormal cloacal septation. As a result, both the bladder and hindgut become
exposed through the abdominal wall defect following apoptosis of the cloacal
membrane. In addition, the cloacal membrane prevents fusion of the genital
folds, causing the genitalia to appear bifid. Meanwhile, in both bladder
exstrophy and epispadias, impaired mesodermal invasion occurs in conjunction
with normal septation of the cloacal membrane. As a result, the abdominal wall
defect exposes either the urethra alone or both the urethra and bladder, depending
on its size. In either case, it appears that the genital folds fuse to a large
extent at the level of the urorectal septum, caudal to the urogenital sinus. In
males, this arrangement would explain the presence of the urethra on the
anterior surface of the undivided penis.
Presentation And Diagnosis
The diagnosis of bladder
exstrophy can be established using prenatal ultrasound performed after 15 weeks
of gestation. The major findings include poor visualization of the bladder, a
lower abdominal bulge, small genitalia (in males), a low-set umbilicus, and a
pubic bone diastasis. If the diagnosis is not established before birth, it is
readily apparent upon delivery.
Treatment
Immediately after birth, the
umbilical cord should be tied with a ligature rather than clamped with plastic
or metal, so as to minimize trauma to the exposed bladder mucosa. Likewise, a
sheet of plastic wrap should be used to cover the anterior abdominal defect and
protect the bladder mucosa from abrasion by towels, diapers, and clothing. A
thorough physical and radiologic assessment should be performed to assess for
the presence of other anomalies.
The relative merits of a
single or staged repair of the exstrophy, epispadias, abnormal ureterovesical
junctions, and abnormal bladder neck have yet to be determined; however, it is
clear that the sooner the exstrophied bladder is closed and the bladder neck
and sphincter are reapproximated, the better the chance for a functional
bladder and long-term urinary continence.
The timing of the initial
closure depends on a number of variables, including the size of the bladder,
the size of the penis in the male patient, the length and depth of the urethral
groove, the width of the pubic diastasis, and the presence or absence of other
associated anomalies. Most exstrophies, however, can be closed within the first
72 hours of the infant’s life, which protects the bladder mucosa from the
environment and facilitates development of the bladder musculature. At the time
of the initial closure, many patients also undergo pelvic osteotomy in which
the ilia and ischia are cut to facilitate reapproximation of the pubic
symphysis. This procedure can reduce tension on the abdominal wall closure, and
it reapproximates the pelvic floor musculature in the midline to improve later
continence. Whether osteotomy is performed or not, the infant’s pelvis is
usually immobilized for up to 1 month after the procedure to facilitate normal
bone alignment.
With current reconstructive
strategies, most patients achieve urinary continence (albeit with clean
intermittent catheterization in a significant proportion) and can lead
satisfying personal and professional lives. Long-term management, however, must
address the psychological effects of this condition, possible sexual dysfunction
(especially in women), and later complications, such as vaginal and rectal
prolapse in women.
