Approach
A patient will usually present complaining of pain on defecation. This pain may continue for some time after defecation as a burning discomfort rather than the initial sharp pain. There is often a history of bleeding at the time of defecation; usually the blood is seen on wiping.[2][3][4]
Physical examination
It is often difficult to examine the patient as they are apprehensive following previous pain on defecation. It is important to reassure the patient that you will not hurt them. On gently parting the patient's buttocks, marked spasm of the anus will most frequently be seen. There may be a skin tag or sentinel pile at the anal verge if symptoms have been present for some time. By parting the buttocks slightly more, the lower end of the fissure can often be seen as a linear split in the skin or a tear-shaped ulcer.[11]
If the fissure is acute, it most often resembles a paper cut. Fissures that are more chronic tend to be slightly wider, have indurated edges, and may have visible transverse fibres of the internal anal sphincter at their base. Fissures are most commonly seen in the posterior midline (99% in males and 90% in females), with the remainder in the anterior midline.[15] Rarely, a lateral fissure may be seen, which may indicate alternative diagnoses of anal ulceration such as Crohn's disease, tuberculosis, sarcoidosis, syphilis, HIV, anal cancer, and ulceration secondary to treatment with nicorandil.[4]
A digital rectal examination should not be performed as this will cause great pain in the majority of patients.[4] If there is any doubt over the diagnosis or any concern regarding aetiology, an examination under anaesthesia can be performed to exclude other diagnoses, including, rarely, a low rectal cancer or anal cancer. An examination under anaesthesia is particularly helpful in older patients, where anal fissure is less common and therefore exclusion of an alternative diagnosis might be appropriate before embarking on nitrate therapy for 6 to 8 weeks.[2][3][16]
If treatment with topical agents is not effective, a more careful history may need to be taken to confirm the diagnosis of primary idiopathic anal fissure. Previous anorectal trauma, including surgery, obstetric history, and a history of chronic diarrhoea, should be specifically asked about. If there is doubt about the diagnosis, or if proper examination is too painful for the patient, examination under anaesthesia is useful.
Further tests
Anal manometry should be considered in women who have had obstetric injury (third-degree tear), as low resting pressure can contraindicate the need for sphincterotomy. Ultrasound examination is a useful adjunct to manometry in this population as it may identify an anatomical cause for low anal sphincter pressure.
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