Fissure in ano is one of the common benign anorectal conditions and can occur at any age. It commonly affects the younger and middle age groups but is sometimes seen at other ages, including infancy and early childhood and has no sex predilection. Ninety percent of anal fissures occur in the posterior midline of the anoderm and are solitary. Ten percent of women and one percent of men may have fissures in the anterior midline (Fig. 4.2). Women who develop symptoms during pregnancy or after childbirth usually have anterior fissure in ano (Jonas et al. 2001). Atypical positions of fissure or multiple fissures (Figs. 4.3 and 4.4) should raise the suspicion of uncommon causes like inflammatory bowel disease, tuberculosis, anal intercourse and anal malignancy, or immunodeficiency syndromes.

Fissures may be classified as primary idiopathic, which is the most common and secondary, based on the etiology. It has also been classified arbitrarily as acute fissure in ano and chronic fissure in ano based on the duration of symptoms and healing. Typically acute anal fissures are those which heal within 6 weeks of duration spontaneously or with medical management. They are superficial and may deepen to expose the underlying internal sphincter. Fissures which have not healed in 6 weeks and developed secondary changes in the form of sentinel tag, hypertrophied anal papilla (Fig. 4.5), induration of the lateral edges of the fissure, relative stenosis secondary to spasm, or fibrosis of the internal sphincter are labeled as chronic, and these often require surgical management (Zaghiyan and Fleshner 2011; Madalinski 2011). Based on location, fissure is classified as typical or atypical. Among the typical sites, posterior fissures are the most common (90 %), while anterior ones are uncommon. Atypical fissures are located at any other site and usually due to some secondary pathology.

In its early stages, a fissure is a simple split in the skin of the anal canal, but there soon develop in connection with it certain secondary changes. One of the most striking of these is a swelling of the skin at the lower end of the fissure, actually at the level of the anal orifice, so that it forms a tag – like swelling the so-called sentinel pile. This is presumably due to low-grade infection and lymphatic edema, and often the tag has a very inflamed, tense, and edematous appearance (Fig. 4.6); later it may undergo fibrosis and persist as a permanent fibrous skin tag even after the fissure has healed.

Quite frequently, the anal valve immediately above the fissure also becomes swollen due to edema and fibrosis and forms a hypertrophied anal papilla. Another feature in a long-standing case is the development of fibrous induration in the lateral edges of the fissure. At any stage, frank suppuration may occur and extend into the surrounding tissues to form a perianal abscess, which may discharge through the fissure into the anal canal or may burst externally to produce a low anal fistula: fissure fistula complex (Fig. 4.7). Usually the external opening of this fistula lies in or close to the midline, a short distance behind the anus, and an anal fissure should always be thought of as the most common cause of such a median low dorsal anal fistula. When the fissure is relatively superficial, the sphincter usually undergoes a tight spasm, but when the fissure deepens and bares the sphincter fibers, this becomes even more pronounced. Eventually after several months, the muscle may become fibrosed in its spastic condition so that a rather fibrotic, tightly contracted, internal sphincter may result.

The etiology and pathogenesis of this condition is poorly understood and hence the confusion in the choice of optimal modality of treatment. It was known for a long time that the tear in anal fissure is caused by passage of hard fecal mass. In 1994, a theory of inverse relationship of anodermal blood flow in the posterior commissure of the anoderm to the internal sphincter resting pressure was postulated by Schouten et al. (1996). The blood supply to the posterior midline of the anal canal has been demonstrated to be significantly lower using Laser Doppler Flowmetry than anywhere else in the anal canal (Klosterhalfen et al. 1989) and hence the increased propensity of occurrence of anal fissures in this region. It has also been found that there is a decrease in the normal spontaneous cyclical anal sphincter relaxation in patients with anal fissure. No single factor can be attributed to the etiopathogenesis of anal fissures, and a combination of factors may be contributory. These can be discussed under the following subheadings:

The most common symptom of fissure in ano is excruciating tearing anal pain after passage of stools associated with passage of minimal amounts of bright red blood which usually lines the stools. Subsequently, it may continue as a severe burning discomfort for few minutes to hours after defecation. To some patients with an anal fissure, the pain is so agonizing that they are frightened to have a motion and may remain in a constipated condition. Some patients complain of perianal pruritus and feeling of wetness in the perianal region. Some patients with a large sentinel tag may become aware of this as a lump at the anus and may complain of having a painful external pile. Sometimes patients with a painful anal fissure develop disturbances of micturition, either dysuria and retention or increased frequency.

During examination, it is essential that extreme gentleness is displayed since fissure in ano is an extremely painful condition and the patient suffering from it is usually very apprehensive of rectal examination. Examination of the perianal region on careful inspection typically shows a superficial mucosal split in acute fissure. This requires gentle parting of the buttocks sufficient to open the anal orifice. A chronic fissure will have raised edges of the mucosal split with varying depth mostly in the posterior midline, exposing the pale-colored internal sphincter at the floor. The induration at the edges gives an impression that of a button hole on palpation. There is often a skin tag at the distal end and a hypertrophied anal papilla at the proximal end (Gupta 2004). Proctoscopy may have to be deferred especially in an acute case in view of pain. The sphincter spasm and the fibrosis may be appreciated during palpation. Occasionally, a fistula may be demonstrated with an infected fissure in ano (Fig. 4.7). Abnormal locations and multiplicity should raise a suspicion, and attempts must be made to rule out specific causes for the occurrence of fissure in ano as described above. Crohn’s fissures are multiple, asymptomatic, and eccentric in location. HIV-disease-related fissures are deep, broad based, or cavitating ulcers with poor sphincter function.

Management strategies are decided based on the acuteness or chronicity of the fissure clubbed with the patients presenting complaints. Etiological factors and complications of fissures also determine the choice of the treatment offered.