IMPERFORATE ANUS

Imperforate Anus : Embryology- Between 4-6 weeks, the cloaca becomes the common depository for the developing urinary, genital and rectal systems. The cloaca is quite promptly divided into an anterior urogenital sinus and a posterior intestinal canal by the urorectal septum. Two lateral folds of cloacal tissue join the urorectal septum to complete the separation of the urinary and rectal tracts.
Diagnostic evaluation include physical exam for clues such as: meconium "pearls", bucket handle
anus, a fistula or meconium at meatus (urethra). Radiography could be of help initially by using the
Wangensteen-Rice "upside-down" film with opaque marker, sacral films, urogram (IVP and cystourethrogram). Through the distal stoma of the initial colostomy a contrast study (colostogram) can be done to further delineate the recto-urethral fistula associated.

Associated Anomalies: (1) Gastrointestinal- 10-20% of patients with imperforate anus have another GI
lesion such as esophageal atresia, intestinal atresia or malrotation. (2) Cardiovascular- approximately 7% have associated CV lesions. (3) Skeletal- approximately 6% have skeletal lesions such as spina bifida or agenesis of the sacrum. (4) Genitourinary- 25-40% of patients will have associated genitourinary anomalies. The incidence is higher with supralevator lesions than with infralevator lesions.

The repair has been revolutionize by Peña approach (Posterior sagittal anorectoplasty procedure). The
most important decision in the initial management of Imperforate Anus (IA) male patient during the neonatal period is whether the baby needs a colostomy and/or another kind of urinary diversion procedure to prevent sepsis or metabolic derangements. Male patients will benefit from perineal inspection to check for the presence of a fistula (wait 16-24 hours of life before deciding). During this time start antibiotherapy, decompress the GI tract, do a urinalysis to check for meconium cells, and an ultrasound of abdomen to identify urological associated anomalies. Perineal signs in low malformations that will NOT need a colostomy are: meconium in perineum, bucket-handle defect, anal membrane and anal stenosis. These infants can be managed with a perineal anoplasty during the neonatal period with an excellent prognosis. Meconium in urine shows the pt has a fistula between the rectum and the urinary tract. Flat "bottom" or perineum (lack of intergluteal fold), and absence of anal dimple indicates poor muscles and a rather high malformation needing a colostomy. Patients with no clinical signs at 24 hours of birth will need a invertogram or cross-table lateral film in prone position to decide rectal pouch position. Bowel > 1 cm from skin level will need a colostomy, and bowel < 1 cm from skin can be approach perineally. Those cases with high defect are initially managed with a totally diverting
colostomy. Diverting the fecal stream reduces the chances of genito-urinary tract contamination and future damage.

The most frequent defect in females patient with imperforate anus (IA) is vestibular fistula, followed by
vaginal fistulas. In more than 90% of females cases perineal inspection will confirmed the diagnosis. These infants require a colostomy before final corrective surgery. The colostomy can be done electively before discharge from the nursery while the GI tract is decompressed by dilatation of the fistulous tract. A single orifice is diagnostic of a persistent cloacal defect usually accompany with a small-looking genitalia. Cloacas are associated to distended vaginas (hydrocolpos) and urologic malformations. This makes a sonogram of abdomen very important in the initial management of these babies for screening of obstructive uropathy (hydronephrosis and hydroureter). Hydrocolpos can cause compressive obstruction of the bladder trigone and interfere with ureteral drainage. Failure to gain weight and frequents episodes of urinary tract infections shows a poorly drained urologic system. A colostomy in cloacas is indicated. 10% of babies will not pass meconium and will develop progressive abdominal distension. Radiological evaluation will be of help along with a diverting colostomy in this cases. Perineal fistulas can be managed with cutback without colostomy during the neonatal period.