To investigate the possible diagnostic role of anal sphincter relaxation integral (ASRI) in high-resolution anorectal manometry (HRAM) for Hirschsprung disease.

We performed conventional anorectal manometry (ARM) in 24 infants (8 with Hirschsprung disease and 16 without Hirschsprung disease) and HRAM in another 21 infants (9 with Hirschsprung disease and 12 without Hirschsprung disease) before and after October 2014. All infants underwent rectal suction biopsy for confirmation of Hirschsprung disease. We quantified rectoanal inhibitory reflex (RAIR) adequacy by calculating the ASRI in HRAM study at pressure cutoffs of less than 10, 15, and 20 mm Hg (ASRI10, ASRI15, and ASRI20, respectively) and investigated the diagnostic utility.

Patients with Hirschsprung disease who underwent HRAM had significantly lower ASRI10, ASRI15, and ASRI20 values than did infants without Hirschsprung disease (P = .0002, .0002, and .0003, respectively), indicating significant difference in internal anal sphincter relaxation during RAIR test between these 2 groups. ASRI10 exhibited a greater diagnostic accuracy, area under the curve, sensitivity, and specificity than did ASRI15 and ASRI20 for Hirschsprung disease. Moreover, the diagnostic accuracy of HRAM for Hirschsprung disease based on ASRI10 <7 mm Hg.s.cm was significantly greater than that of conventional ARM (P = .02).

ASRI10 may be indicative of the adequacy of RAIR by HRAM in infants, thus assisting the diagnosis of Hirschsprung disease. The diagnostic accuracy of HRAM (based on the ASRI10 value) is greater than that of conventional ARM for Hirschsprung disease. ASRI10 may be used in an automatic HRAM analysis system for the diagnosis of anorectal motility disorders.