Endoanal ultrasound assessment of sphincter defects and thinning – Correlation with anal manometry

Background and study aimsThis study aims to determine if anal sphincter defects/thinning observed at endoanal ultrasound correlates with anal pressures recorded at anal manometry.Patients and methodsA total of 30 consecutive patients with history suggestive of anal sphincter pathology underwent anal endosonography with documentation of internal and external sphincter defects/thinning. The same patients underwent anal manometry with documentation of maximum resting and maximum squeeze pressures. Patients with a sphincter defect (SD) were compared to patients without a sphincter defect (NSD) and both groups were compared with respect to findings in manometry. The Mann–Whitney U test was used for statistical analysis. This study was approved by the Institutional Ethics Committee.ResultsA statistically significant correlation was found between decreased maximal resting pressure and decreased internal anal sphincter (IAS) thickness or an IAS defect. The correlation between MSP and external sphincter pathology was significantly less consistent in our study.ConclusionOur study showed a statistically significant correlation between maximum resting pressure and observation of internal sphincter defects at endoanal ultrasound. The patients with documented internal sphincter defects have significantly reduced maximum resting pressures. There was however, no correlation between external sphincter defects and decrease in maximum squeeze pressure as has been observed in other studies. Until a manometry cut-off can be set to discriminate between the absence and presence of defects, both manometry and ultrasound should be offered to patients with history suggesting anal sphincter pathology.