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Objectives: The aim of this study was to correlate clinical findings of anal sphincter defects and function with a sonographic diagnosis of significant sphincter defects.

Methods: This is an observational cross-sectional study on women seen 6 to 10 weeks after primary repair of obstetric anal sphincter injuries (OASIs). All patients underwent a standardized interview including the St Mark incontinence score, a digital rectal examination, and 3-/4-dimensional transperineal ultrasound imaging.

Results: Two hundred forty-five patients were seen after primary repair of OASIs. Mean age was 29 (17-43) years. They were assessed at a median of 58 (15-278) days postpartum. One hundred fifty-seven (64%) delivered normal vaginally, 72 (29%) delivered by vacuum, and 16 (7%) delivered by forceps. A comparison of external anal sphincter (EAS) and internal anal sphincter ultrasound volume data and palpation was possible in 220 and 212 cases, respectively. Sphincter defects at rest and on contraction were both detected clinically in 17 patients. Significant abnormalities of the EAS were diagnosed on tomographic ultrasound imaging in 99 cases (45%), and significant abnormalities of the internal anal sphincter were diagnosed in 113 cases (53%). Agreement between digital and sonographic findings of sphincter defect was poor (k = 0.03-0.08). Women with significant EAS defects on ultrasound were found to have a lower resistance to digital insertion (P = 0.018) and maximum anal squeeze (P = 0.009) on a 6-point scale. The difference was however small.

Conclusions: Digital rectal examination does not seem to be sufficiently sensitive to diagnose residual sphincter defects after primary repair of OASIs. Imaging is required for the evaluation of sphincter anatomy after repair.