Incidence and risk factors for secondary failure after acute obstetric sphincter injury repair - an audit of 239 women.

Aim: The rate of secondary failure after obstetric sphincter injury repair is unknown, with the literature reporting rates ranging from 0.1% to 53%. We aimed to perform an audit to identify the rate and risk factors for failure of sphincter repair in a cohort of postpartum women using endoanal ultrasound (EAUS) and manometry, assessing the risk factors and impact of these events.

Method: Prospective data were collected within a 2 year period from patients who attended the perineal clinic at Eastern Health. Variables of primary repair and presence of postpartum complications were recorded and subsequently analysed.

Results: Of 239 patients with obstetric anal sphincter injury (OASI) included, 100 (41.8%) had EUAS evidence of sphincter defects. Only 20% with secondary repair failure were symptomatic with faecal or flatal incontinence at a mean follow-up of 23.4 months postpartum. Patients with secondary repair failure had lower anal resting (p = 0.006) and maximum squeeze pressures compared with patients with intact repairs (p < 0.001). In terms of variables that were investigated, namely location, operator hierarchy, type of repair and material used, none had a statistically significant correlation with secondary repair failure of OASI. Postpartum complications had an overall incidence of 12.7%, and those with any complication were found to have an increased rate of secondary failure of repair (p = 0.157).

Conclusion: Using EAUS to confirm secondary failure of repair, incidence was 41.4% in this cohort. There were no identifiable modifiable variables that reduced the risk of secondary failure of repair. Further prospective research with increased sample size and longer follow-up periods is required to assess the validity of the findings.