Redundancy in the International Anorectal Physiology Working Group Manometry Protocol: A Diagnostic Accuracy Study in Fecal Incontinence.

ABSTRACT

BACKGROUND: Anorectal manometry (ARM) is essential for identifying sphincteric dysfunction. The International Anorectal Physiology Working Group (IAPWG) protocol and London Classification provide a standardized format for performing and interpreting ARM. However, there is scant evidence to support timing and number of constituent maneuvers. AIMS: To assess the impact of protocol modification on diagnostic accuracy in patients with fecal incontinence. METHODS: Retrospective analysis of high-resolution ARM recordings from consecutive patients based on the current IAPWG protocol and modifications thereof (1) baseline rest period (60 vs. 30 vs. 10 s); (2) number of abnormal short squeezes (SS) out of 3 (SS1/SS2/SS3) based on maximal incremental squeeze pressures over 5 s; (3) resting anal pressures (reflecting recovery) at 25-30 versus 15-20 s after SS1. RESULTS: One hundred patients (86 F, median age 55 [IQR 39-65]; median St. Mark's incontinence score 14 [10-17]) were studied. 26% and 8% had anal hypotonia and hypertonia, respectively. Compared with 60-s resting pressure, measurements had perfect correlation (κ = 1.0) over 30 s, and substantial correlation (κ = 0.85) over 10 s. After SS1, SS2, and SS3, 43%, 49%, and 46% had anal hypocontractility, respectively. Correlation was substantial between SS1 and SS2 (κ = 0.799) and almost perfect between SS2 and SS3 (κ = 0.9). Compared to resting pressure of 5 s before SS1, pressure recordings at 25-30 and 15-20 s after SS1 were significantly correlated. CONCLUSIONS: A 30-s resting anal pressure, analysis of 2 short-squeezes with a 20-s between-maneuver recovery optimizes study duration without compromising diagnostic accuracy. These findings indicate the IAPWG protocol has redundancy.