A 2-day-old male newborn has not passed any meconium since birth. Examination of the newborn reveals no anal orifice. The newborn is scheduled for a colostomy.
An imperforate anus may occur with several presentations.
Type 1: Anal stenosis occurs at the anus or 1-4 cm above the anal level and is due to the incomplete rupture of the anal membrane. There may be an associated fistula with the genitourinary system or the perineum.
Type 2: Imperforate anus occurs when the obstruction is due to a persistent membrane.
Type 3 (the most common presentation): Imperforate anus is associated with the rectum ending blindly at a considerable distance above the imperforate anus. The rectum may have a fistulous connection to the urethra, bladder, base of the penis or scrotum, or vagina.
Type 4: There is a normal anus and anal pouch, but the rectum ends blindly.
The newborn may present because no stool has been passed in the first 24 hours, because the newborn has a distended abdomen, or because the newborn passes stool near the vaginal opening, the base of the scrotum, the bladder, or the penis.
Imperforate anus may also occur with other congenital abnormalities, such as VACTERL (vertebral, anal, cardiac, tracheal, esophageal, renal, and limb) and REAR (renal, ear, anal, and radial) syndromes. In general, the higher the anorectal anomaly is located, the greater the incidence of associated anomalies. The incidence of anorectal malformations is about 1 in 5000 newborns.
The newborn should be screened for associated abnormalities preoperatively, especially for cardiac and tracheoesophageal anomalies.
Anesthesia should be adapted to the extent of the abdominal distention, the operation (simple perineal anoplasty, temporary colostomy, or extensive abdominoperineal repair), and whether there are any associated cardiovascular and renal problems.
Consider rapid-sequence induction or awake intubation if the abdomen is distended.
Maintain anesthesia with an inhalational agent in an air-oxygen mixture. Use muscle relaxants to allow better operating conditions. If there is no need to identify the anal sphincter. Use narcotics judiciously.
Nitrous oxide should be avoided to prevent further bowel distention.
Ensure adequate hydration, as there may be large insensible fluid losses, large third space losses with bowel manipulation, and additional considerations if there is a bowel perforation. Balanced salt solutions or colloid at a rate of 10 mL/kg/h of surgery or more may be needed.
Consider the risk of sepsis if there was bowel perforation.
Monitoring includes urine output, blood pressure, and quality of heart tones. Invasive monitoring is not required for the healthy patient.
If there are other associated life-threatening anomalies or if a large volume of fluids was required to keep the patient hemodynamically stable, you should ...