Obstetric anal sphincter injuries: are defunctioning colostomies required?

The incidence of obstetric anal sphincter injury in the UK is rising. This condition leads to significant morbidity in otherwise healthy women. Significant long-term complications of obstetric anal sphincter injury include anal incontinence, ano-vaginal or recto-vaginal fistula and psychological distress. Current management of third and fourth degree perineal tears post-vaginal birth is primary repair. This article discusses the role of a defunctioning colostomy in women with severe perineal tears in the immediate postnatal period. A defunctioning colostomy is a surgical procedure to open a section of colon (large bowel) onto the abdominal wall; a stoma bag is then worn over this to collect faeces. The rectum and anal canal are not used (defunctioned), while the stoma is in place and the perineum is healing. This article describes the purpose and operative steps of colostomy formation and reviews current published evidence of outcomes in those with colostomy formation for obstetric anal sphincter injury. It also addresses the difference in clinical approach between obstetricians and colorectal surgeons in relation to the management of severe obstetric anal sphincter injury and highlight the need for multidisciplinary input.