28-year-old Hu, a female, white-collar company, recently regretted a matter. The original no problem, but because of busy work, want to sleep more in the morning, the defecation time to work after the schedule, the result is often hold stool. I didn’t feel anything at first, but after a month, I suddenly had blood in my stool and pain in my anus. I don’t know where the stool, which was on time, has gone, but it was meaningless for a few days. When I went to the hospital, I found out that I had an anal fissure. How did I get this disease? Was it caused by holding in my stool? On the one hand, it reduces the sensitivity of the bowel receptors, causing constipation, and on the other hand, it affects the function of the sphincter, causing spasm of the internal sphincter. It is believed that there are four key factors in the formation of anal fissures: 1. abnormal stool The anal canal does not open for no reason, first of all because of the impact or friction from external forces. The anal canal is responsible for defecation, and feces pass through it every day. If the feces is too thick and hard, the anal canal will be poorly adapted at this time, and as a result, the anal canal will be cracked by friction. In addition, some people found that not only constipation, diarrhea can also produce anal fissures, which accounts for 4-7% of the causes of anal fissures, the specific reasons to be analyzed. 2, internal sphincter spasm Anal fissures come from impact, and poor adaptation of the anus to deal with this impact is the most important factor that ultimately produces anal fissures. There is a certain pressure in the anal canal, which is conducive to anal closure, and the anal canal pressure mainly comes from the internal sphincter. A high tension of the internal sphincter causes a significant increase in the resting pressure of the anal canal, when the anal canal is not stretched enough, and when a dry and hard stool passes through, a fissure will be produced. The internal sphincter is a smooth muscle, but when stimulated by fecal residue and intestinal fluid, it spasms, causing severe pain. Why is the tone of the internal anal sphincter elevated? The main causes are: (1) Inflammatory irritation. When inflammation occurs in the intestine, anal canal or sinus, it stimulates the tension of the internal sphincter. (2) Acidic fecal stimulation. Just as excess stomach acid can irritate the intestinal mucosa leading to gastric or duodenal ulcers and painful stomach cramps. Feces are generally alkaline, but when they become acidic when there is a dysbiosis, they stimulate the internal sphincter to spasm. (3) Exposure of the sphincter muscle. (4) Emotional abnormalities, such as when angry or nervous. 3.Ischemia Not when the anus is cracked, anal fissure is definitely formed, but only when the fissure does not heal or has repeated attacks. Local ischemia is the most important cause of anal fissure. There are two reasons for ischemia: (1) vascular distribution. The local blood supply to the anus comes from the anal artery, which is distributed from both sides to the middle and crosses in front of and behind the anus, resulting in two weak areas of distribution in front of and behind the anus. (2) Spasm of the internal sphincter. Excessive tension of the anal canal and poor blood circulation. (4) Anatomical defects The external anal sphincter forms two triangular fissures in front and behind the anal canal, which lack sufficient support for the anal canal, but produce fissures when feces hit. It is worth noting that the occurrence of anal fissures is caused by the accumulation of long-term, multiple etiologies, which include the reduction of the elasticity of the anal canal skin, impaired blood supply, easy damage to the anterior and posterior walls, reduced adaptability of the internal sphincter, anal injury, etc.