Introduction and hypothesis: The aim was to analyze the correlation between residual anal sphincter (AS) defects and pelvic floor muscle (PFM) strength on anal incontinence (AI) in patients with a history of obstetric AS injuries (OASIS).
Methods: From September 2012 to February 2015, an observational study was conducted on a cohort of females who underwent repair of OASIS intrapartum. The degree of OASIS was scored intrapartum according to Sultan's classification. Participants were assessed at 6 months postpartum. Incontinence symptoms were evaluated using Wexner's score and PFM strength using the Modified Oxford Scale (MOS). 3D-endoanal ultrasound was performed to classify AS defects according to Starck's system. Correlation between Sultan's and Starck's classifications was calculated using Cohen's kappa and Spearman's rho (Rs) test. The impact of residual AS defects and PFM strength on AI was analyzed using a multiple regression model.
Results: A total of 95 women were included in the study. Good correlation (κ= 0.72) was found between Sultan's and Starck's classifications. Significant positive correlation was observed between Wexner's score and both Sultan's (p = 0.023, Rs =0.212) and Starck's (p < 0.001, Rs =0.777) scores. The extent of the residual AS defect was the most relevant factor correlating with AI symptoms. In patients with severe AS injuries, higher MOS values were associated with lower Wexner's score.
Conclusions: The degree of AS tear measured intrapartum was the most important factor related to AI after primary repair of OASIS. PFM strength was associated with lower incontinence symptoms in the postpartum period.
Keywords: Anal incontinence; OASIS; Pelvic floor muscle.