480 High Resolution Transrectal Ultrasound Findings Predict Manometric Responders to Biofeedback Therapy for Anal Incontinence

Abstract

INTRODUCTION: In the United States, over 8% of adults are affected by anal incontinence (AI), and a large percentage of these patients have a history of damage to their pelvic floor. High resolution three-dimensional transrectal ultrasound (TRUS) can be used to assess for microstructural damage to the pelvic floor muscles. Biofeedback (BFB) therapy is a key intervention for AI in addition to anti-diarrheal medications or fiber supplements but it relies on strengthening and improving coordination of existing pelvic floor structures. TRUS is a promising tool to predict meaningful improvement with BFB. METHODS: This is a retrospective analysis of patients enrolled in BFB for AI between 2015 and 2018 at a tertiary referral motility program. Survey and high resolution anorectal manometry (HR-ARM) data were collected at baseline and during each AI BFB visit. Of the 36 patients who met criteria, 9 had TRUS as part of their care. TRUS images were obtained using a high frequency (7-15MHz) ultrasound probe. Fisher's exact test and t-test were used for statistical analysis. Improvement in maximum squeeze pressure on HR-ARM was defined as increase by greater than 30% or ≥29 mmHg from baseline to final session. RESULTS: Patients were on average 62 years old (SD 10 years), one was male, and the mean BMI was 28.0 (SD 6.7). Five of the 8 women had a suspected obstetric etiology to their AI, while two patients attributed symptoms to surgery, one to radiation therapy, and one to neurologic injury. TRUS revealed microstructural defects in the external anal sphincter (66.7%), internal anal sphincter (77.8%), puborectalis muscle (55.6%), and perineal body (66.7%) as shown in Table 1 Three patients had damage to all 4 structures and this was significantly associated with lack of improvement in squeeze on ARM (P = 0.047). Absence of an external anal sphincter defect trended towards correlation with improvement in squeeze (P = 0.07). Baseline levator hiatus abnormalities did not predict lack of improvement in manometric characteristics (P = 0.17). CONCLUSION: TRUS is an emerging tool to identify microdamage to structures of the pelvic floor including internal and external anal sphincter complexes and other key support structures. As BFB for patient with AI aims to retrain muscle coordination, absence of multiple deficits identified on TRUS may predict positive responders to BFB therapy.