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

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. To assess the impact of protocol modification on diagnostic accuracy in patients with fecal incontinence. 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. 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. 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.