Anal dilatation

Information has been excerpted from VisualDx clinical decision support system as a public health service. Additional information, including symptoms, diagnostic pearls, differential diagnosis, best tests, and management pearls, is available in VisualDx.


Laxity of the anus and anal dilatation may be found with neurologic disorders and chronic constipation but may also be consistent with sexual abuse. Anal dilatation of any size is considered a normal reflex if stool is present in the rectal vault or if dilation occurs after the child has been in the prone knee-chest position for more than 30 seconds. However, anal dilatation of 20 mm or greater, without stool in the rectal vault, is suspicious for abuse.

Childhood sexual abuse is a problem of epidemic proportions affecting children of all ages and economic and cultural backgrounds. Although awareness of child abuse is increasing, it may be challenging to differentiate findings attributable to sexual abuse from those of other benign anogenital skin conditions.

Look For:

The anus can be examined in the supine, lateral, or knee-chest position. It is important to note that the child’s position may influence the appearance of anatomy.

A digital exam is rarely needed during a sexual abuse or routine pediatric exam. The size of the anus can be measured without digital exam, but if a digital examination is performed, the presence and consistency of stool should be noted.

All skin findings should be noted during the exam of the anus. This includes other benign findings such as acrochordons (skin tags) and hemorrhoids. The presence of associated bruises around the anus, scars, fissures, or anal tears – especially those that extend into the surrounding perianal skin – should be noted. Findings suggestive of traumas such as these increase the likelihood of sexual abuse.

In addition to the genitals, look for any skin contour changes over the sacrum and coccyx that could be overlying abnormality of the distal spinal cord. Also confirm the presence of an anal wink by noting contraction of the anus when the skin adjacent to the anus is stroked.

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