High-resolution Anorectal Manometry Measures Are More Accurate Than Conventional Measures in Detecting Anal Hypocontractility in Women With Fecal Incontinence

Background & Aims: Anorectal manometry is a common test of anal tone and contractility. However, existing measures are often criticized for their poor ability to detect functional differences between individuals with presumably normal sphincter function and individuals with fecal incontinence. We investigated whether new measures, derived from high-resolution anal manometry (HR-ARM), more accurately identify incontinent women with abnormal sphincter function than measures from conventional anal manometry (C-ARM). Methods: We performed a prospective HR-ARM study of 85 healthy female volunteers (median age 41 years; range 18–68 years) and 403 women with fecal incontinence (median age 55; range 18–91 years) from June 2013 through December 2015. We compared the diagnostic accuracy of conventional measurements of contractility (C-ARM squeeze increment) and tone (C-ARM resting pressure) (the reference standards), with HR-ARM measures (HR-ARM squeeze increment, HR-ARM contractile integral, HR-ARM resting average, HR-ARM rest integral). We also investigated associations between symptom severity and structural sphincter integrity. Results: We identified anal hypocontractility in 129 women with fecal incontinence using the C-ARM squeeze increment (32% sensitivity; likelihood ratio, 6.4), in 189 women using the HR-ARM squeeze increment (47% sensitivity; likelihood ratio, 9.4), and in 220 women using the HR-ARM contractile integral (55% sensitivity; likelihood ratio, 11.0). In contrast, HR-ARM measures of anal tone did not particularly outperform conventional measures (31% sensitivity for HR-ARM resting average vs 28% for C-ARM resting pressure). Ninety-eight of the 206 patients with fecal incontinence who were classified as having normal anal function, based on C-ARM measures, were reclassified as having abnormal function based on HR-ARM measures. Conclusion: In a prospective study of healthy women and women with fecal incontinence, we demonstrated that the newly developed HR-ARM contractile integral increased the sensitivity of detection of anal hypocontractility, from 32% to 55%, compared with conventional measurements of squeeze.