• Not determined

• The hindgut comes in contact with the cloacal membrane during the sixth week of fetal development. At this time, the hindgut is divided into a ventral urogenital and dorsal rectal component. By the eighth week, the dorsal half perforates to the exterior. In imperforate anus, the process is arrested during this critical period.
• There are many anatomic variants of imperforate anus. From the prognostic point of view, the most important is classification, distinguishing two main types: supralevator (high) and translevator (low). Separate is a group of cloacal malformations in which the urinary genital and digestive systems drain to a common channel that communicates with the perineum.
• A fistula communicating from the gut to the urogenital system or to the external opening is present in 90% of cases. In females, most commonly the fistula leads to the opening in the posterior fourchette of the vagina (in low lesions) or to the upper vagina (in high lesions). In males, the fistula leads to the raphe of the scrotum (in low lesions) or to the urethra (in high lesions).

• Imperforate anus can be an isolated defect or part of the syndrome or association.
• Syndromic disorders that contain imperforate anus are associated with defects on chromosomes 6, 7, 10, and 16.

• Other anomalies are present in one-third of patients with an imperforated anus.
• Imperforate anus can be associated with vertebral and cardiac anomalies, tracheoesophageal fistula and, renal and limb anomalies (VACTERL association).
• Other anomalies associated with imperforate anus include intestinal atresia, malrotation, omphalocele, annular pancreas, urologic anomalies, spinal anomalies, duplicate uterus, septate vagina, vaginal atresia, and absence of rectal muscles.

• A majority of children are diagnosed in the first days of life by abnormal findings on physical examination.
• Failure to pass meconium, a history of constipation, and signs of low intestinal obstruction (abdominal distention and vomiting) should mandate reexamination of perianal area.

• Lesion presents as either no opening, an inadequate caliber of anus, or an anterior malposition of the opening.
• Physician should attempt to localize the opening of the fistula and look for associated anomalies.
• Evaluation for lumbosacral neurologic function should be done. Anal wink can usually be elicited, because a vertiginous external anal sphincter is present in a majority of the cases.

• Invertogram: After sufficient time for a transit of gas (>12 hours after birth), the child is placed in an upside-down position for 3 minutes, after which a lateral view of the pelvis is obtained.
• Lumbosacral films to evaluate for vertebral anomalies: An MRI of the spine should be considered to look for a tethered cord.
• Renal ultrasound, voiding cystoureterogram, and IVP can be used to evaluate for urinary tract anomalies.

• Surgery should be performed by an experienced surgeon.
• High lesions require an emergent diverting colostomy and pull-through procedure with a Pena midsagittal anorectoplasty at 3 to 9 months of age. The colostomy is closed after the anoplasty has healed and any necessary secondary dilations have been completed.
• Complications of surgery include stricture of the anocutaneous anastomosis, rectourinary fistula, mucosal prolapse, constipation, and incontinence.

Q: Is this an isolated defect in my child?
A: Often, imperforate anus can be associated with multiple other anomalies and not necessarily isolated. Renal and vertebral anomalies must be excluded.

Q: What is the genetic basis for this defect?
A: Imperforate anus can be associated with chromosomal anomalies or can be an isolated problem.

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