ANORECTAL MALFORMATIONS

Anal atresia (imperforate anus)

Clinical Features

  • The child is born without an anal opening. This should be detected during the routine examination of a newborn.
  • The mother may also report failure of the baby to pass stool.
  • Congenital abnormalities are frequently multiple; a careful general examination of the baby is an important prerequisite.

Investigations

  • It is urgent and important to determine whether the abnormality is high or low. Do an x-ray (Invertogram) 6 hours after birth (air has collected in the large intestine). This x-ray may have to wait for 24 hours for rectal gas to collect.
  • Procedure for doing the Invertogram:
    • Strap a coin on the site of anus.
    • Hold the infant upside down for 3–5 minutes.
    • Put the thighs together and parallel to one another.
    • Take a radiograph and measure the distance between the metal coin and the shadow in the rectum. If the distance is over 2.5cm the abnormality is high; or draw a line on the radiograph from the tip of coccyx to the pubic
      crest (pubo-coccygeal line). If the gas shadow is above the line, the abnormality is high.

Management

For high abnormalities, do the following:

  • Nasogastric suction
  • Intravenous fluids
  • Keep baby warm
  • Refer to a specialized centre for surgery.

Low abnormalities are easy to diagnose, simple to treat, and the outlook is good.

There are 4 types of low imperforate anus:

  • The stenosed anus: The opening is in the normal position but very minute. The first treatment is careful dilatation with well lubricated hegar dilators and thereafter digital dilatation. The mother is taught how to dilate the anus.
  • The ectopic anus: The anus is situated interiorly and opens into the perineum in boys or vagina in girls.
  • A careful search will reveal the low subcutaneous opening. This should be distinguished from the high vaginal opening or fistulae. The treatment is a pull through operation.
  • The covered anus: The treatment is as for stenosed anus
  • The membranous anus: Treatment is a cruciate incision.