Cloacal exstrophy represents a spectrum of rare congenital anomalies that are thought to arise from maldevelopment of the cloacal membrane, which prevents migration of mesenchymal tissue and impedes normal development of the lower abdominal wall. The cloacal membrane separates the coelomic cavity from the amniotic space during the early embryogenic period. The position and the timing of the disruption of the cloacal membrane will determine the variant of the exstrophy that results. For example, inferior perforation results in epispadias; midperforation results in classic exstrophy; and the superior perforation results in superior-vesicle fissure (Jeffs, 1987). When cloacal exstrophy is present in its classic form, the constellation of severe abnormalities is among the most difficult for the pediatric surgeon to reconstruct. It consists of exstrophy of the urinary bladder, exstrophy of the small or large intestine, anal atresia, hypoplasia of the colon, omphalocele, and malformed genitalia, and associated neural tube defects in 50% of cases (Figure 64-1) (Fujiyoshi et al., 1987).

The anatomy in cloacal exstrophy is complex, with a ventral abdominal wall defect consisting of an omphalocele at the superior margin of the defect and exposed bowel and bladder at the inferior extent (Figure 64-2). The hemibladders are separated in the midline by a zone of intestinal mucosa. Each hemibladder may have a ureteral orifice and the intestinal zone separating the hemibladders may have the orifices of the proximal gut superiorly and the distal gut inferiorly, with one or two appendiceal orifices in between (Warner and Zeigler, 1993). The proximal bowel orifice often prolapses in the characteristic “elephant-trunk” deformity. The distal gut is a blind pouch, as these infants all have imperforate anus. All genetically male cases have associated genital anomalies, including undescended testicles and a bifid penis, with each half attached to widely separated pubic rami (Johnston and Penn, 1966).

Although cloacal exstrophy was recognized as early as 1909, it was not until 1960 that the first successful reconstruction was reported (Rickham, 1960; Warner and Zeigler, 1993). It is only in recent decades that repair of this complex anomaly has been routinely undertaken. For years most infants were allowed to die because of the multiple and complex congenital anomalies (Molenaar, 1996). However, in the past two decades, survival after reconstruction for cloacal exstrophy has increased to 90% to 100%, albeit with substantial and lifelong physical and emotional burdens for these patients and their families (Manzoni et al., 1987).

During early development, the cloacal membrane separates the coelomic cavity from the amniotic cavity. The cloaca is first evident in the midline as an area in which ectoderm and endoderm are in opposition, with no mesoderm in between. By the 4th week of development, the cloacal membrane forms the anterior wall of the urogenital sinus at the base of the allantois. Cephalad and lateral to the cloacal membrane are the primordia of the genital tubercle. These primordia enlarge and fuse in the midline superior to the cloacal membrane to form the genital tubercle. At the same time there is in growth of mesoderm toward the midline, increasing the distance between the body stalk and the cloacal membrane, setting up the development of normal infraumbilical body wall. The cloaca becomes divided into the urogenital sinus and the rectum by the urorectal septum, which extends in a medial and caudal direction to the cloacal membrane (Pohlman, 1911; Patten and Barry, 1952).

Patten and Barry (1952) suggested the caudal displacement theory for the genesis of cloacal exstrophy. According to this theory, abnormal caudal displacement of the paired primordia of the genital tubercle is responsible for cloacal exstrophy. Epispadias alone would occur if fusion of the primordia in the midline occurred at the level where the urorectal septum joins the cloacal membrane. Exstrophy of both bowel and bladder would be present if even further caudal displacement of the primordia occurred at a level caudal to the anal portion of the cloaca.

In contrast, Marshall and Muecke (1962) suggested that the “wedge effect” of an abnormally large cloacal membrane was responsible for cloacal exstrophy. This abnormally large cloacal membrane acts as a wedge to the developing structure of the abdominal wall. Rupture of this membrane prior to descent of the urorectal septum and fusion of the genital tubercles results in the midline infraumbilical defect, exposure of bladder and bowel mucosa, with bifid genitalia that have epispadias. In a chick embryo model, Muecke (1964) was able to demonstrate that a plastic graft placed in the region of the cloacal membrane produced a wedge defect with persistent cloacal membrane and varying degrees of infraumbilical defects. These theories do not account for involvement of bowel, prolapse of ileum, and foreshortened gut in cloacal exstrophy.

Magnus (1969) suggested that a loop of midgut or hindgut prolapses between bladder halves and becomes strangulated. Alternatively, Johnston (1913) suggested that the growth of the hindgut is restricted by its involvement in the exstrophy.

More recently Bruch et al. observed sonographic progression in a fetus with a dilated cloacal abnormality at 18 weeks of gestation associated with oligohydramnios and hydronephrosis. Repeat ultrasound examination performed at 24 weeks of gestation demonstrated rupture of the cloacal abnormality with resolution of both the hydronephrosis and oligohydramnios. This newborn had the classic features of cloacal exstrophy, challenging previous theories of its embryogenesis (Bruch et al., 1996).

Cloacal exstrophy is associated with anomalies of organ systems other than the central defect in up to 85% of cases (Hurwitz et al., 1987) (Table 64-1). Anomalies of the urinary tract are common and in several series occurred in 42% to 60% of cases (Spencer, 1965; Johnston and Penn, 1966; Tank and Lindenauer, 1970; Zeigler et al., 1986; Hurwitz et al., 1987). Vertebral anomalies occur in 48% to 78% of patients (Spencer, 1965; Tank and Lindenauer, 1970; Hurwitz et al., 1987) and myelodysplasia in 29% to 46% of patients (Zeigler et al., 1986; Hurwitz et al., 1987).

Fortunately, cloacal exstrophy is rare, with a frequently quoted incidence of 1 in 200,000 to 1 in 400,000 livebirths (Zeigler et al., 1986). However, this may be an underestimate because many fetuses with cloacal exstrophy die in utero or are stillborn (Paidas et al., 1994). Its incidence has been reported to fluctuate in some areas, suggesting possible epidemics (Evans et al., 1985). In one study, preconceptional maternal exposure to smoking was significantly more common in parents whose fetus has cloacal exstrophy than in other related anomalies (Gambhir et al., 2008).

The anatomic features of cloacal exstrophy are seen on ultrasound examination, thus enabling prenatal diagnosis of these complex congenital abnormalities (Meizner and Bar-Ziv, 1985; Mirk et al., 1986; Romero, 1988; Nyberg et al., 1990; Langer et al., 1992). Cloacal exstrophy should be suspected when there is a lower abdominal wall defect with absence of a normal bladder. Splaying of the pubic rami may also be present. The association of neural tube defects along with these findings also supports the diagnosis.