The anal canal is a tube of about 3 cm in length, surrounded by internal and external sphincters, and collapsed by Levator ani muscle at the ano-rectal junction. The lining of the upper 2/3rd of the anal canal is derived from the ectoderm of the cloaca. It has a visceral innervation, and hence is relatively insensitive. The lining of the lower 1/3 rd is derived from the ectoderm of the proctoderm and has a somatic innervation via the inferior rectal nerve. Painful sensation may arise from the perianal skin, the anoderm or the surrounding muscles. Anal Fissure: It is a split at the junction of perianal skin and the anoderm. The lesion is a longitudinal tear of the anoderm ie of the lower 3rd of the anal canal, extending from the dentate line to the anal margin. It almost always lies in the midline. Anal fissure may be superficial or deep. If superficial the floor is formed by the longitudinal muscle fibers lying in the sub mucosa. If deep, the base consists of the transversely running white fibers of the internal sphincter.
The sex ratio is almost equal. In Male about 90% are posterior and 10% anterior. It is due to unequal support of rectal mucosa over the racket shaped attachment of external sphincter in coccyx. In Female anterior fissures are more common, due to unequal support of the rectal mucosa by a damaged pelvic floor.
Commonest in young adults. Occasionally occurs in infants and children, rare in the elderly. In children there is usually associated constipation.
Etiology is unknown.
High resting anal fissure: According to this theory chronic anal fissure is thought to result from a non healing laceration of the anoderm due to constipation. However only 20 % of patients give a history of constipation.
Ischaemic origin: Traumatic breech of anoderm normally heals but patients with pre existing raised sphincter tone will have impaired microvascular perfusion of the posterior mid line anoderm and will heal poorly. This theory supported by the postmortem angiographic study shows minimal arterial connection between the terminal branches of the bilateral inferior rectal arteries at the posterior mid line. So, the chronic anal fissures are most certainly a result of the combined effect of a hypertonic anal sphincter and a decreased ano dermal blood flow residing in a non-healing ischaemic ulcers of the anoderm.
Pain – 90 % 0f the patients have pain on defecation and the pain is typically severe and it may be last 20 to 30 minutes, but seldom longer. So, the fear of defecation may lead to constipation. Scybala form and the inevitable act of defaecation is then accompanied by excruciating pain and reopening of the fissure.
Bleeding is frequently occurs.
Other symptoms are?