Background: This study investigates the inter- and intraindividual variability of normal values and, thus, the reproducibility of anorectal manometry.
Materials and methods: Following a standardized protocol, three anorectal manometries were performed 4 h apart on 2 days of investigation, with an interval of 4 weeks, in ten healthy volunteers. Measured parameters in all 60 manometries were: sphincter length (SL), resting pressure (RP), maximum squeeze pressure (MSP), relaxation of the internal anal sphincter (RIAS), and rectal compliance (RC). Interindividual variability was expressed as standard deviation from calculated mean values and intraindividual variability was tested with Wilcoxon's test for tied samples and Spearman's rank correlation test.
Results: A large interindividual variability was found for all measured parameters, except for SL, reflecting the extensive absolute range of measured values. Median intraindividual variability among the six individual measurements and between both measurement days revealed that MSP, RIAS and RC are parameters which were not reproducible in this volunteer study. A significant correlation between the results of the repetitive measurements and, thus, a good reproducibility was only found for the parameters SL and RP.
Conclusions: Anorectal manometry has only limited diagnostic value; although rather exact quantifications of individual parameters can be achieved, the impact of these measurements should be regarded rather critically, since only SL and RP appeared to be reproducible parameters.