INTRODUCTION
Obstetric anal sphincter injuries (OASIS) occur in approximately 3-6% of vaginal deliveries and are considered a significant risk factor for late onset faecal incontinence. [1] Continence is a complex multi-factorial mechanism which relies crucially on intact anal sphincters, as well as rectal compliance, rectal sensation, stool consistency and neural coordination. Primiparity, large birth weight, instrumental deliveries, parietal or vertex presentation, and a prolonged second stage of labour (which may lead to denervation of the pelvic floor) are obstetric factors which increase the risk of a sphincter injury, graded as third or fourth degree perineal tears in the widely accepted standardised classification. [2-4]
Late post-partum faecal incontinence is an underdiagnosed pathology which affects almost one in three women following OASIS and dramatically reduces quality of life. [5] Impaired sphincter and neurological function after OASIS repair is a likely contributor, in combination with a diminishing trophic effect of oestrogen on pelvic floor function as patients age and menopause approaches. In recent years, irritable bowel syndrome (IBS) which affects 10-15% of the population has been shown to double the risk of faecal incontinence after OASIS in the early post-partum period. [6, 7] In this population however, it is not known how repair of OASIS, remaining sphincter defects and IBS interact.
The aim of this study therefore is to investigate the effect of IBS on severity of faecal incontinence symptoms after primary repair of OASIS.