nance imaging thereafter are useful radiologic modalities to establish the diagnosis. Furthermore, patients may have other spinal anomalies besides tethered cord such as syringomyelia and myelomeningocele.
Perineal fistulas in both male and female have traditionally been called "low" defects. In these cases the rectum opens in a small orifice, usually stenotic and located anterior to the center of the sphincter (Figure 3). Most of these patients have excellent sphincter mechanisms and a normal sacrum. In males, the perineum may exhibit other features that help in recognition of this defect, such as a prominent midline skin bridge (known as 'bucket handle') or a subepithelial midline raphe fistula that looks like a black ribbon because it is full of meconium. These features are externally visible and help diagnose a perineal fistula. A simple anoplasty enlarges the stenotic orifice and relocates the rectal orifice posteriorly within the limits of the sphincter complex. The operation is called a "minimal posterior sagittal anoplasty". It is performed with the patient positioned prone with the pelvis elevated; multiple fine silk sutures are places at the mucocutaneous junction of the bowel orifice for traction. A short (1–2 cm) midsagittal incision is made posterior to the fistula site, dividing the entire external sphincter complex. The fistula and lower part of the rectum are carefully dissected to permit mobilization of the rectum for backward placement within the limits of the sphincter complex. The perineal body, that area where the fistula was located, is repaired with a few long-term absorbable sutures .
Anorectal malformations (ARM) represent a spectrum of abnormalities ranging from mild anal anomalies to complex cloacal malformations. The etiology of such malformations remains unclear and is likely multifactorial. There are however reasons to believe there is a genetic componenet. As early as the 1950s, it was recognized that there was an increased risk for a sibling of a patient with ARM to be born with a malformation, as much as 1 in 100, compared with the incidence of about 1 in 5000 in the general population. Since that time there have been reports of families with 2 or more affected members and associations of ARMs with multisystem syndromes. In particular, mutations in specific genes encoding transcription factors have been described in patients having Townes-Broks syndrome, Currarino's syndrome, and Pallister-Hall syndrome, each of which have autosomal dominant modes of inheritance. In addition, it has been found that there is not only an increased incidence of ARM in patient with trisomy 21 (Down's syndrome), but that 95% of patients with trisomy 21 and ARM have imperforate anus without fistula, compared with only 5% of all patients with ARM. Based on this evidence, it is likely that the mutation of a variety of different genes can result in ARM, or that the etiology of ARM is multigenic .
The radiologic evaluation of a newborn with imperforate anus includes an abdominal ultrasound to evaluate for urologic anomalies. In the case of persistent cloaca, a distended vagina (hydrocolpos) can be identified. Plain radiographs of the spine can show spinal anomalies such as spina bifida and spinal hemivertebrae. Plain radiographs of the sacrum in the anterior-posterior and lateral projections can demonstrate sacral anomalies such as a hemisacrum and sacral hemivertebrae. Also, the degree of sacral hypodevelopment can be assessed, and a sacral ratio can be calculated measuring the distances between key bony structures. A spinal ultrasound in the newborn period and up to age 3 months (at which time the sacrum becomes ossified) can look for evidence of a tethered spinal cord and other spinal anomalies. A crosstable lateral radiograph can help show the air column in the distal rectum in the small percentage of patients for whom clinical evidence does not delineate in 16–24 hours the likely anorectal anomaly.
After the newborn period, on an outpatient basis after the colostomy (see colostomy) has been created, high press