Assessment of sonographic quality of anal sphincter muscles in patients with faecal incontinence

Objective The main application of endoanal ultrasonography (US) in evaluation of faecal incontinence is to identify surgically correctable sphincter defects. The aim of our study was to determine whether qualitative changes in echogenicity and in uniformity of internal (IAS) and external (EAS) anal sphincter muscles detected on endoanal US correlate with other anal laboratory tests and modified Wexner faecal incontinence functional score. Method Records on 99 patients having complete information on anorectal manometry, faecal incontinence scoring and available endoanal US imaging of the anal sphincters were included in statistical analysis. Anatomic appearance and changes in echogenicity of the anal sphincter muscles were recorded according to the proposed scoring system. Endoanal US defect and quality component scores for IAS and EAS as well as the total score were correlated with anal laboratory tests and incontinence score using Spearman's correlations test. Results There was a trend for correlation between IAS quality score and incontinence score (P = 0.06), but no correlation for IAS defect score. EAS defect score had a significant negative correlation with maximum squeeze pressure (MSP) (P = 0.031). Distal EAS quality score had a significant correlation with incontinence score (P = 0.002). EAS total score correlated with MSP (P = 0.02) and incontinence score (P = 0.006). Endoanal US total score was significantly correlated with incontinence score (P = 0.006), maximal resting (MRP) (P = 0.035) and MSP (P = 0.045) and high pressure anal canal zone length (P = 0.03). Conclusion Sonographic morphology of anal sphincter muscles correlates with anal laboratory tests and functional incontinence score. Qualitative ultrasound scoring instrument may improve evaluation of patients with faecal incontinence.