An anal fissure is essentially a tear or split in the anoderm at the dentate line. 80-90% of these are located in the posterior midline. Anterior midline locations are far less common, occurring in 5-10% of all cases. Symptoms of anal fissures often arise soon after the passage of a hard bowel movement through the anal canal. This is believed to cause stretching and subsequent tearing of the anoderm. Occasionally, this may be associated with a bout of severe diarrhoea.
The anterior and posterior midlines are the weakest areas of the anal canal. It is at these locations that the external sphincter fibers decussate. In addition, the midline locations are areas where the skin is tethered more adherently to the sphincter complex. During the process of defecation, partial eversion of the anal canal leads to more tension arising in these areas. Coupled with the less adequate anodermal blood flow here, ischemia occurs and results in an ulcer being formed.
Patients are placed in a left lateral position with both hips and knees flexed towards the chest. Adequate lighting is mandatory. Simple spreading of the buttocks will easily reveal the distal anal canal and the fissure or ulcer complex. It is often not possible to perform an anoscopic examination in these patients and this is not recommended. The classical pain arising from the fissure can be elicited by using a cotton-tipped swab stick to stroke the fissure bed.Fissure Examination
Patients with anal fissures present with a very classical history of a 'searing' or 'tearing' type of pain which is associated with each bowel movement. This is usually accompanied by bright red per rectal bleeding. Symptoms of pruritus or perianal skin irritation may also be present.
The main goal of treatment is to interrupt the cycle of sphincter spasm and further tearing of the injured mucosa, thereby allowing the fissure to heal. This is carried out by advising the patient on the four pillars of treatment:
The medical literature is filled with numerous studies addressing the efficacy of non-surgical treatments for anal fissures. It is therefore imperative that physicians be cognizant of the evidence that is available for each one of these. The following serves to summarize the treatment options the current available evidence on their efficacy.
This is indicated when a trial of medical treatment has failed to produce any significant healing of the fissure, which is most commonly manifested as a persistence of pain. The goal of this is once again, to effect relaxation of the internal anal sphincter. This is achieved by an internal sphincterotomy, which essentially involves the surgical division of the internal anal sphincter from its distal most end to the level of the dentate line, or the most proximal limit of the fissure. The procedure is routinely performed as a day case, with the patient under either general or regional anaesthesia. It is performed through a small incision at the anodermal junction overlying the inter-sphincteric groove. This incision is placed laterally to avoid what is known as a keyhole deformity, hence the term lateral internal sphincterotomy.
In patients who have had a previous history of internal sphincterotomy, or who have poor sphincter function, an alternative procedure is typically offered. These include advancement flaps or fissurectomy with or without adjunct medical treatments such as botulinum injection and topicals. Evaluation by a colorectal surgeon is recommended in these group of patients.