Activity of the internal anal sphincter during the first days of life.

Manometric recordings of the internal anal sphincter activity are frequently used in the diagnosis of Hirschprung's disease. Normally, there is a relaxation of the internal sphincter in response to a rectal distension, but this is absent in Hirschprung's disease. In order to study the normal physiology during the first days of life, 17 healthy full-term infants were examined daily with ano-rectal manometry during the first four days of life. Resting anal pressure was lower than in older children. Internal sphincter relaxation was recorded in all infants but one on the first day, in all on the second and finally in all but one on the third and fourth days. The results indicate that anorectal manometry may be used in the diagnosis of Hirschprung's disease also in the newborn period. However, repeated examinations may be necessary and the diagnostic reliability may be somewhat lower than in older children.