Anorectal manometry in the newborn

Anorectal manometry was performed in 32 newborn. There were 18 preterm and 14 fullterm infants, mean ages 6.1 and 7.1 days respectively. The rectoanal inhibitory reflex (RIR) was positive in 31 of the newborn, and the relaxation waves produced by rectal distention were recorded along the anal canal and were directly correlated to intensity of the stimulus. In the remaining patient RIR was negative, due to Hirschsprung's disease, confirmed at surgery. The length of the anal canal was 10.3 +/- 2 mm. in preterm newborn infants and 14.7 +/- 2.9 mm, in fullterm (p < 0.0001). These findings suggests that presence of RIR is independent of the weight, gestational age and birth age of the infant, and that anal canal length is correlated with the weight of the infant. We conclude that anorectal manometry, in the neonatal period, is a simple, reliable and safe method to test anorectal functionality, including the study of Hirschsprung's disease.