Bladder exstrophy is a congenital abnormality that results in an “inside-out” bladder,
where the bladder protrudes out of the abdomen, leaving the inside of the bladder exposed
to the outside environment.
Normally, in the first trimester, endoderm in the hindgut expands to form the cloaca,
which is a temporary structure that connects the urinary, digestive, and reproductive tracts.
Separately, the ectoderm forms the anterior abdominal wall.
At around eight weeks of development three important things happen.
First, the anterior abdominal wall matures and forms the muscles and connective tissue
of the lower abdomen.
Second, the cloaca splits to form the urogenital sinus and rectum, the urogenital sinus later
goes on to become the urinary and genital ducts, as well as the urinary bladder.
And third, the cloacal membrane opens up to the outside of the body, creating openings
for the urogenital tract and anus.
All right, so bladder exstrophy occurs when the developing bladder and urethra herniate
anteriorly and this causes some problems.
First, it prevents the normal development of the lower abdominal wall which leaves it
open.
Second, it prevents fusion of the pelvis leaving a wide split at the symphysis pubis.
Also, most cases of bladder exstrophy involve epispadias, which is where the urethra exits
the top of the penis, but the opposite is not true, not all cases of epispadias involve
bladder exstrophy.
One way to kind of think about the final result is to imagine the bladder and urethra, and
making a cut through the top of the urethra and bladder, and also imagine that cut goes
up through the symphysis pubis as well as the abdominal wall.
After that, imagine pushing on the bladder from the bottom until it’s inside out, and
this is essentially is what the final defect in bladder exstrophy looks like, and that
bladder pushes through the abdominal wall into the outside world.
In addition to this, bladder exstrophy causes other changes as well.
For example, the anus is usually more anteriorly located.
Also, in boys the anterior part of the penis is shortened, and in girls, the vagina is
wider and shorter and more vertically oriented.
The exact reason that bladder exstrophy happens in some infants is unknown, but one theory
is that the mesenchymal cells fail to migrate between the endoderm of the cloaca and the
ectoderm of the anterior abdominal wall.
Without mesenchymal support, the cloacal membrane becomes unstable and opens to the outside
prematurely.
And this creates a hole in the lower abdominal wall which exposes the internal structures
to the outside.
Having a bladder and urethra exposed to the outside environment can lead to complications
like incontinence as well as an increased risk of urinary tract infections.
As far as diagnosis, goes, the defect is clinically obvious when a baby is born, but is can also
be diagnosed earlier on a prenatal ultrasound.
Generally, within the first few weeks of life, the bladder and urethral defect are surgically
closed, but sometimes staged surgeries are needed over months or years.
All right, as a quick recap, bladder exstrophy is a congenital problem where the bladder
protrudes through the front of the abdominal wall, and it’s often accompanied by epispadias.
It can cause incontinence and increase the risk of urinary tract infections, and requires
early surgical correction.