Qualitative and quantitative evaluation of internal anal sphincter function in the newborn.

One-hundred-and-one normal neonates were examined manometrically in the first day of life to assess anorectal function. In order to overcome some of the difficulties in subjective interpretation of results, the stimuli used and the response pattern seen in the anal canal were measured. In the unstimulated state, all subjects demonstrated rhythmical changes in anal canal tone. Mean maximal intraluminal pressure in the anal canal decreased significantly after 10 hours of age and after the first meconium stool. Only five out of the 101 examined on the first day of life had an abnormal manometric response. It is significant that none of these had passed meconium at the time of examination, and that all had a normal response pattern at the age of 28 hours. In 20 of these babies the sensitivity of the rectoanal reflex was measured and found to be significantly increased on the third day of life compared with the first. The quantitative changes in anorectal reflex function in the newborn, are thought to be related to the state of physiological ;constipation' which exists in utero and in the early neonatal period. The results indicate that a normal response pattern can be obtained in healthy babies after the first day of life. Consequently, anorectal manometry will be meaningful as a diagnostic method thereafter in the neonatal period. Further, it is suggested that measurement of the stimulus and the response will add useful information and reduce subjective error in interpretation of results.