Anal fissures are small ulcers in the skin layer of the anal canal below the anal tooth line, oriented parallel to the longitudinal axis of the anal canal, about 0.5-1.0 cm long, poke-shaped or oval, with severe pain and difficulty in healing. Anal fissure is one of the common diseases in anorectology, taking the third place after hemorrhoids and anal fistula. The disease is most common in young and middle-aged patients, according to Reinhard, 2364 patients, with a peak age of 43 years. 60% of anal fissures occur in men of all age groups, while more than twice as many fissures occur in women than in men under 20 years of age. 10% of women develop anal fissures after childbirth.
The pathogenesis of anal fissures is so far unknown, and the theories are numerous and largely inferential.
1. The theory of injury
Traditionally, it is believed that dry and hard stool is the cause of anal fissure. Blaisdell proposed that the shallow external sphincter fibers and the lower part of the external sphincter skin form a horizontal Minor triangle at the back of the anus, where the skin of the anal canal lacks muscle support and is a weak area, which is easily torn when dry and hard stool is passed, but only 1/4 of the patients with anal fissure have a history of constipation, and some diarrhea is the cause of anal fissure instead. Hananel investigated 772 patients with anal fissures and found that only 10% of them had difficulty in defecating before treatment, while 75% of them had 1-3 bowel movements per day. It can be concluded that most patients with anal fissures are not caused by what is usually called dry and hard stool tearing the skin, and they are not conclusive evidence of anal fissures.
2. Epithelial theory
Histological studies confirm that the epithelium of the anal canal skin of patients with anal fissures is keratinized and loses its elasticity. The keratinization may persist or worsen under the effect of stimulating laxatives, chronic diarrhea caused by various reasons or alkaline stools, resulting in inflammation and loss of elasticity, and acute anal fissures may easily become chronic and extremely difficult to heal.
3.Infection theory
According to this theory, anal fissure can be caused by infection in the anal fossa. Since the anal glands are mostly located in the posterior part of the anal canal, it seems to explain that anal fissures tend to occur in the posterior part of the anal canal. Chronic inflammation can lead to skin fibrosis and loss of elasticity, so it is assumed that anal fissure and anal fossa infection can be causal.
4. Neuromuscular theory
In patients with anal fissure, after rectal filling, the internal sphincter muscle does not produce normal reflex diastole, but produces abnormal excessive contraction. This phenomenon can explain the spasm of the sphincter muscle in patients with anal fissure. This phenomenon can explain the spasm of the sphincter in patients with anal fissures, the severe pain during defecation, and the delayed non-healing.
5.The theory of residual embryonic tissue
Some scholars believe that during the formation of the anal canal in the embryonic period, the original anal concavity was snapped upward into the lower end of the hindgut to form the anorectal sinus, and this sinus closed to form the anorectal band, or some scattered epithelial cell clusters remain, these embryonic leftovers are poorly differentiated tissues, which are prone to infection or lesions, and the trauma to the epithelium of the anal canal often causes repeated infections here, and finally forms chronic anal fissure. This theory is still controversial in academic circles.
6.Local ischemia theory
The morphological study of capillaries suggests that the capillaries inside the internal sphincter at the posterior median line are sparse and that anal fissure may be an ischemic ulcer, and the increased pressure of the internal sphincter during anal fissure may reduce the perfusion pressure of the mucosal skin area. Ischemia is indeed an important factor in the pathogenesis of chronic anal fissures.
In summary, anal fissures are not caused by a single factor, but are the result of long-term interaction of multiple factors. Anal fissures can occur in a second, but it may take several years for them to form.
Prevention of anal fissures.
(1) Keep your diet reasonably regulated to keep your bowels open, do not force hard stools after they form, and apply warm saline enemas or corkage into your anus to lubricate your bowel movements.
(2) Promptly treat inflammation of the anal saphenous fossa to prevent the formation of ulcers and subcutaneous fistulas after infection.
(3) Medical personnel should pay attention to gentle and standardized movements during anal examination to prevent injuries caused by manipulation and instruments.
(4) Promptly treat intestinal diseases such as ulcerative colitis clonorchiasis to prevent complications of anal fissures.