Imperforate anus

Alternative names
Anorectal malformation; Anal atresia


Imperforate anus is a congenital absence or obstruction of the anal opening.

Causes, incidence, and risk factors

Imperforate anus is a malformation of the anorectal region that may occur in several forms. The rectum may end in a blind pouch that does not connect with the colon. Or, it may have openings to the urethra, bladder, base of penis or scrotum in boys, or vagina in girls. A condition of stenosis (narrowing) of the anus or absence of the anus may be present.

The malformations are caused by abnormal development of the fetus, and many are associated with other birth defects. Imperforate anus is a relatively common congenital malformation that occurs in about 1 out of 5,000 infants.


  • absence of anal opening  
  • misplaced anal opening  
  • anal opening very near the vaginal opening in the female  
  • no passage of first stool within 24 to 48 hours after birth  
  • stool passed by way of vagina, base of penis or scrotum, or urethra  
  • abdominal distention

Signs and tests

A physical examination with check for anal patency in the newborn will show the malformation.

A lower abdominal X-ray or contrast enema may be recommended.


The infant should undergo evaluation for other anomalies, especially genital, urinary and spinal. Surgical reconstruction of the anus is required. If the rectum connects with other organs, repair of these organs will also be necessary. A temporary colostomy is often required.

Expectations (prognosis)
The outcome is usually good with treatment, depending on the exact anatomy of the birth defect. Some affected infants may never develop adequate bowel control, depending on the location of the defect.


  • intestinal obstruction  
  • bowel incontinence or constipation

Calling your health care provider
This disorder is usually discovered when the newborn infant is first examined. Call your health care provider if a child that was treated for imperforate anus develops abdominal pain, or fails to develop any bowel control by the age of 3.

As with most birth defects, there is no known prevention.

Johns Hopkins patient information

Last revised: December 5, 2012
by Potos A. Aagen, M.D.

Medical Encyclopedia

  A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | 0-9

All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.