Aims: To establish the accuracy of anorectal manometry (ARM) with reference to operative rectal biopsy in the investigation of children under 1 year of age with defaecation difficulties.
Materials and methods: The records of all infants who underwent ARM and operative rectal biopsy at our centre between 1994 and 2007 were reviewed. ARM was performed by a consultant paediatric surgeon in each and under ketamine anaesthesia, as operative rectal biopsy was taken.
Results: There were 81 patients (49 males, 32 females). The median age at investigation was 2 months (range 0.1-11 months). Thirty-three patients (41%) had Hirschprung's disease. No patient with a normal recto-anal inhibitory reflex (RAIR) had Hirschprung's disease (100% negative predictive value). No patient with Hirschprung's disease exhibited a reflex (100% sensitivity). The specificity and positive predictive value of ARM for Hirschprung's disease were 83% and 80%, respectively. Bowel habit normalised in 88% of patients with a reflex within 1 year.
Conclusions: In children under 1 year of age, Hirschprung's disease is very unlikely in the presence of a RAIR. The specificity and positive predictive value of ARM for the diagnosis of Hirschprung's disease are inferior to those of rectal suction biopsy, and therefore, it cannot be recommended for use as a sole diagnostic tool for this disease. ARM may be a useful investigation in patients where the histologic specimen is inadequate and/or functional constipation is the most likely diagnosis. If RAIR is present, rectal biopsy may not be required.