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| Bladder Exstrophy |
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IntroductionBladder exstrophy is part of a spectrum of anomalies that may involve the bladder, pelvis, intestinal tract, and external genitalia. The most common form of bladder exstrophy is classic exstrophy, which involves a widened pelvis with an anterior diastasis, an open bladder, and a complete epispadias. The mildest form is epispadias, in which a patient may have a closed bladder but widened pelvic symphysis. The most pronounced expression is cloacal exstrophy, which usually involves all of the above findings, as well as omphalocele and, sometimes, a lumbosacral neural tube defect. Cloacal exstrophy often includes anomalies of the spine and extremities. An orthopedic surgeon may be consulted about prognosis of the pelvic defect, assistance during closure of the bladder (especially in an old child), and treatment of associated anomalies.EtiologyThe etiology of exstrophy is unknown. The critical step in development is a failure of ingrowth of mesoderm between the layers of the cloacal membrane.1 The cloacal membrane is the caudal end of the embryonic abdominal wall. It initially forms the anterior boundary of the bladder and hindgut. Mesenchymal ingrowth allows formation of the anterior part of the pelvis and the abdominal wall muscles. A defect in this membrane leads to the development of a large open bladder and urethra. In patients with cloacal exstrophy, the intestines are also exposed.EpidemiologyThe incidence of bladder exstrophy is between 1:10,000 and 1:50,000 live births. Males are more commonly affected, with a ratio of at least 2.5:1. Classic exstrophy is the most common type seen, with cloacal exstrophy being about one-fifth as common. The risk of recurrence for a family having a child with exstrophy is approximately 1:100. Many patients are currently diagnosed prenatally.Clinical FeaturesAffected patients have a midline defect in the anterior abdominal wall at the level of the pubic symphysis, exposing an open bladder and urethra. This defect measures at least 3 cm to 4 cm at birth in classic exstrophy. The bladder is a flat plate instead of a closed sac. In cloacal exstrophy, the abdominal wall defect is much larger, and the lower intestinal tract is variably exposed. A spinal examination and neurological examination of the lower extremities should be performed. Often, in patients with cloacal exstrophy, a lower lumbar neurological deficit is present due to lipomeningocele or myelomeningocele. Hip dislocation, foot deformity, or partial sacral agenesis may occur.Radiographic FeaturesOn radiographs, separation of two paired pubic bones, which usually are symmetrically formed in patients with classic exstrophy, can be seen. This separation is typically 4 cm to 5 cm at birth and increases steadily with age (Slide 1A, Slide 1B, Slide 2A, and Slide 2B). The separation is normally a constant value of approximately 1 cm throughout life. The iliac wings are externally rotated approximately 15° each and assume a flattened shape. The anterior (ischiopubic) portions of the pelvis are slightly underdeveloped and have a decreased transverse diameter. The hips, apart from being in a retroverted position, rarely show dysplasia. In patients with cloacal exstrophy, the diastasis is large (Slide 3A, Slide 3B, and Slide 3C) and many other spinopelvic anomalies exist: posterior laminar defects, vertebral body anomalies, sacroiliac asymmetry, and hip dysplasia.
Other Imaging StudiesOther imaging studies are rarely necessary for patients with classic exstrophy. In patients with cloacal exstrophy, computed tomography (CT) may show the sacroiliac and pelvic malformations more completely than radiograph. Magnetic resonance imaging (MRI) of the spine may be valuable for patients with cloacal exstrophy if there is evidence of an anomaly.PathoanatomyStudies of the pelvis by CT, MRI, and dissection of anatomic specimens of classic exstrophy have established the following characteristics2-5 (Slide 4):
Natural History (Long-Term Without Treatment)The function of the pelvis and hips in an untreated patient with classic bladder exstrophy is generally good. Children walk at a normal age, although they have an increased external foot-progression angle. This angle becomes less pronounced over time.3,4,6 Athletic ability is not impaired. Adults with exstrophy have an increased incidence of pain in the region of the sacroiliac joints. One natural history study suggested an increased incidence of degenerative disease of the hip in patients with uncorrected exstrophy.2 However, the number of patients in the study was small and the affected patients appeared to have a degree of acetabular dysplasia, which is not commonly seen in most patients with classic exstrophy. It is not proven that osteotomy of the pelvis for exstrophy is necessary to protect against premature osteoarthritis of the hip in the absence of associated acetabular dysplasia. Reports of uterine prolapse in adult females with exstrophy can be found in the literature, but the frequency of this is unknown. Patients with exstrophy are usually fertile.Treatment RecommendationsA pediatric urologist performs the reconstruction in several stages, including closure of the bladder and lower abdominal wall soon after birth, followed by epispadias closure at the same time or a later date. Surgery to achieve continence is commonly performed after the age at which children are normally continent and may consist of bladder neck suspension and/or collagen injections. Patients who remain incontinent are offered a bladder augmentation and an umbilical stoma for catheterization. Finally, in older children, occasionally plastic surgery is an option to optimize the appearance of the perineum. Generally, orthopedic surgery of the pelvic deformity is indicated as part of one of these procedures only if it is needed to achieve urological goals. These goals include achieving a closed bladder, urinary continence, and acceptable appearance of the perineum. In the past, male patients with cloacal exstrophy were reconstructed as females with appropriate endocrine supplementation due to extreme abnormalities of the external genitalia. However, long-term studies have shown that psychological distress at maturity may occur after this practice, so families are given both gender options.Nonsurgical treatment Patients with exstrophy who have been successfully managed without osteotomy may not need any procedures for the pelvic bones. They may have been closed with soft tissue rotational procedures to manage a mild-to-moderate sized exstrophy defect. Neonates whose bladders are operated upon at birth can usually be closed by manually approximating the two halves of the pelvis and strong suture between the pubic bones placed by the urologist. The lower extremities are immobilized in traction, a cast, or splint. The mobility to allow the approximation of the pubis likely occurs through plastic deformation of the sacral ala and laxity of the sacroiliac joints. Although the pelvis gradually assumes its original diastasis over time, the tissue relaxation achieved by the above sequence lasts long enough for the midline soft tissue closure to become mature in most patients. Surgical treatment Indications. The most common indication for orthopedic surgery on the pelvis is a bladder and lower urinary tract that cannot be closed without approximation of the pubic bones. This is usually the case in a patient who presents for closure after the first month of age or who has failed a previous closure without osteotomy. Another indication is an older patient with a closed bladder who requires osteotomy and pubic re-approximation for continence. A final indication is an older child in whom perineal reconstruction is aided by bringing the pelvis closer together. This decreases the width of the perineum and restores a near normal appearance to the external genital structures. Patients who have acetabular dysplasia with classic exstrophy should have osteotomy. Options. The benefit of approximating the divergent urogenital structures with aid of pelvic osteotomy was first described by O'Phelan.7 The investigators used bilateral vertical iliac osteotomies through a posterior approach, with a midline wire to hold the pubic bones together.8 This necessitated turning the patient from prone to supine in the middle of the procedure. Since then, other approaches have been developed. Transverse supra-acetabular iliac osteotomies from an anterior approach were described in the 1980s by several surgeons3,4 (Slide 2A, Slide 2B). An oblique osteotomy of the ilium has also been described, which is midway between the two prior approaches and can help to bring the wings of the ilium together.9 Anterior pubic ramotomy is a simple procedure that can aid in the approximation of the two pubic bones, although the effect is not as pronounced as iliac osteotomy. The pelvis may be immobilized using bed rest and a cast, traction, external fixation, or internal fixation. A combination of external and internal fixation provides the most consistent results. Author's practice. The author's preference is to assist the urologist in closing all classic exstrophy within a few days after birth, when circulating relaxin is maximal and the pelvic bones are soft. Most babies can be successfully closed without osteotomy. The author prefers to immobilize patients in modified Bryant's traction with the legs suspended vertically so that the pelvis is slightly off the bed. This maintains an anterior closing force to the anterior pelvis while the closure heals. Other surgeons use casts or splints to adduct or internally rotate the hips. For patients whose bladders reopen, who present late, or who fail procedures for continence, the author prefers anterior supra-acetabular iliac osteotomies. In children older than 1 year of age, an additional closing-wedge greenstick osteotomy is added lateral to the sacroiliac joints to rotate the iliac wings together. Pins are inserted for external fixation, and the urologist closes the bladder, perineum, and abdomen. The external fixator is then assembled. In patients with cloacal exstrophy, the diastasis is large and the bone is soft. An anterior plate is helpful in maintaining the closure. For this reason, the author prefers to defer cloacal closure until the child is at least 6 to 12 months of age and plating is feasible (Slide 3A, Slide 3B, Slide 3C). All children have some recurrence of the diastasis as they grow after an osteotomy, although it is less than it would have been without closure. Patients who have an osteotomy at the youngest ages have the greatest rate of recurrence. The goal of maintaining pelvic approximation while the urological reconstruction heals appears to be successful in the majority of patients. ComplicationsIn one large series, the complication rate of orthopedic treatment of exstrophy was 4%.10 Complications were classified as either bony or neurologic at the osteotomy site, complications of traction, or infection. Bony complications included vertical migration or nonunion after posterior iliac osteotomies, as well as inadvertent osteotomy through the sacroiliac joints (Slide 5A and Slide 5B), since the procedure does allow visualization of these joints. The most frequent neurologic complication was femoral nerve palsy after anterior osteotomy. Femoral nerve palsy appears to be due to medial pressure and tension on the nerve and resolves spontaneously within 3 months. Two sciatic palsies, by mechanisms unknown, were reported. Complications of immobilization include skin breakdown from wrapping the two legs tightly adducted together. Deep infection at the osteotomy site does not occur with increased frequency compared to other elective surgeries, despite the proximity to the incontinent bladder.
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