Evaluation of obstetric anal sphincter injury

Abstract

Faecal incontinence presents with a female to male preponderance of 8:1 consistent with vaginal delivery as the principal causative factor. It results in serious social and psychological morbidity. Anal sphincter dysfunction following vaginal delivery generally results from direct muscular damage to the anal sphincter and/or cumulative damage to the pudendal nerves. Increasing attention is being focused on this relatively common and significant form of puerperal morbidity. Women with symtoms of faecal incontinence postpartum or a documented history of third degree tearshould be assessed where possible, in a multidisciplinary perineal clinic. Specific questioning concerning faecal incontinence is important because such symptoms are rarely volunteered. A detailed obstetric and medical history is essential. Application of a detailed bowel function questionnaire is helpful in establishing a ‘continence score’ which permits easy interpretation and comparison of disability. It also facilitates a comparative analysis of symptoms following treatment. Clinical signs suggestive of sphincter injury include perianal soiling, absence of the cutaneous anal reflex,patulous anus and local scarring but further physiological assessment is required to delineate the precise nature and prognosis of sphincter injury. This evaluation should include: endoanal ultrasound, which examines the anatomical integrity of the sphincter and anal mamometry, which assesses sphincter tone and contractile function. Pudental nerve function is tested using a combination of tests including electromyography (EMG) studies of anal sphincter muscle, pudendal nerve terminal motor latency and the clitoral anal reflex.