Review Chronic anal fissure I. Lindsey, O. M. Jones, C. Cunningham and N. J. McC. Mortensen Department of Colorectal Surgery, John Radcliffe Hospital, Headley Way, Headington, Oxford OX3 9DU, UK Correspondence to: Mr I. Lindsey (e-mail: lindseyilinz@yahoo.com) Background: The treatment of chronic anal fissure has shifted in recent years from surgical to medical. Methods: A Medline search of studies relevant to modern management of chronic anal fissure was undertaken. Results: Traditional surgery that permanently weakens the internal sphincter is associated with a risk of incontinence. Medical therapies temporarily relax the internal sphincter and pose no such danger, but their limited efficacy has led to displacement rather than replacement of traditional surgery. Emerging medical therapies promise continued improvement and new sphincter-sparing surgery may render traditional surgery redundant. Conclusion: First-line use of medical therapy cures most chronic anal fissures cheaply and conveniently. The few non-responders can be targeted for sphincter assessment before traditional surgery. If the initial good results of new sphincter-sparing surgery are confirmed, it may be possible to avoid any risk of incontinence, while achieving high rates of fissure healing. Paper accepted 19 January 2004 Published online in Wiley InterScience (www.bjs.co.uk). DOI: 10.1002/bjs.4531 Introduction Anal fissure is a painful tear or split in the distal anal canal. Most acute fissures heal spontaneously but a proportion become chronic; this review article is restricted to the management of chronic fissure. Chronicity is defined by both chronology and morphology. The chronological definition is rather loose, but most surgeons regard persistence beyond 6 weeks as a reasonable point when an acute fissure, now unlikely to heal with conservative treatment, may be considered chronic. Morphologically, the presence of visible transverse internal anal sphincter fibres at the base of a fissure typifies chronicity and provides a more clear-cut definition. Associated features include indurated edges, a sentinel pile and a hypertrophied anal papilla. Widely differing healing rates have been reported and for the future it is important that chronic fissures should be defined, and the defining criteria made clear in published studies. Some studies have used a mix of chronological and morphological definitions, as noted above, but it would be useful if a universal definition for trial entry could be agreed and used. A reasonable definition might be ‘the presence of visible transverse internal anal sphincter fibres at the base of an anal fissure of duration not less than 6 weeks’. Chronic fissure is usually associated with internal anal sphincter spasm, the relief of which is central to promoting fissure healing. Treatment has undergone a transformation in recent years from surgical to medical 1 , both approaches sharing the common goal of reducing this spasm. There is both anatomical 2 and physiological 3 evidence that the anal canal is relatively poorly perfused, especially in the posterior midline, and this relative ischaemia is rendered critical when compounded by the internal anal sphincter spasm that has long been recognized to be associated with fissures 4 . This review examines some of the evidence for concern about surgical treatment of chronic fissures, outlines the physiological basis for the pharmacological manipulation of internal anal sphincter tone, and proposes sphincter-saving approaches. Surgery The aim of treatment is to cure the fissure by reducing the associated abnormally raised resting anal pressure. Traditionally, surgery has been the mainstay of treatment, producing a permanent reduction in maximum resting pressure (MRP) by manual dilatation or internal sphincterotomy. Copyright  2004 British Journal of Surgery Society Ltd British Journal of Surgery 2004; 91: 270–279 Published by John Wiley & Sons Ltd