Anatomically speaking, the distribution of nerves in the anorectum is bounded by the dentate line (the dentate line is about 2.5 cm from the edge of the anus, which is the boundary between the rectum and the anal canal), and diseases above the dentate line are innervated by vegetative nerves and are not sensitive to pain, so diseases above the dentate line, such as internal hemorrhoids, proctitis, rectal polyps and early rectal cancer, often have no obvious pain. Below the dentate line belongs to somatic innervation and is sensitive to pain, so anal pain indicates that the lesion is below the dentate line, i.e., the anal canal and perianal area. Since there are internal and external sphincters around the anal canal, these muscles are easily stimulated to cause spasm and lead to local ischemia, so the pain of the anal canal is greater than that of the perianal area. The clinical characteristics of common diseases with anal pain symptoms are described as follows: 1. Anal fissure The pain of anal fissure is related to defecation. This is because the anal canal is fissured, and when feces enters the canal, the canal dilates and causes anal burning pain, followed by contraction and spasm of the anal sphincter, resulting in severe pain lasting from a few minutes to several hours, and some people even continue until the next bowel movement. Another manifestation of anal fissures is blood in the stool, which is less frequent than dripping blood at times, blood on the surface of the stool or blood on the hand paper. Constipation is both a direct cause and a clinical feature of anal fissures. Patients are afraid of defecation because of the pain, and often intentionally prolong the interval between defecations, causing the feces to remain in the rectum for too long and the water to be absorbed, resulting in rectal constipation, and the damage to the fissure wound is further aggravated by dry and hard feces at the next defecation. If you’ve got an anal fissure, you’ll be able to form a sentry hemorrhoid at the outermost end of the fissure, leading to an enlarged anal papilla in the anus. 2, inflammatory external hemorrhoids Anal edge skin folds protrude swelling, some in the shape of a ring, some swelling wrapped around the anus half circle, mostly accompanied by anal pain, some patients feel pain and itching intermittently. After the swelling subsides, the anal margin remains superfluous to form connective tissue external hemorrhoids. 3.Thrombosed external hemorrhoids When the patient struggles to defecate or does actions that increase abdominal pressure, such as lifting heavy objects and getting up, the small blood vessels under the skin of the anal verge rupture and blood accumulates under the skin to form a blood clot, and the patient often feels a sudden and severe pain in the anus. There can be dark purple round nodules under the skin of the anal verge, mostly in the left middle or right middle of the anal verge, such as 5-7 days, the clot will absorb by itself and the pain will be relieved. 4.Inset of internal hemorrhoid prolapse Mostly seen in the second or third stage of internal hemorrhoids, the internal hemorrhoid prolapses and then retracts by itself or resets by hand, which does not cause anal pain, but when the internal hemorrhoid prolapses and then does not retract in time, the inset occurs, resulting in local blood flow obstruction, causing edema, thrombosis, and even erosion and necrosis. At this time, the patient feels that the anus is painful and swollen, and there is a feeling of blockage in the anus. The examination shows that the anal edge is swollen in a circular manner, the internal hemorrhoid is purple or partially blackened outside the anus, the surface of the hemorrhoid nucleus is eroded, and there is secretion and odor when it is accompanied by infection. 5, perianal abscesses Because of the different depths of abscesses, the performance is different. Deep abscesses mostly have systemic symptoms, such as fever, lumbosacral discomfort, cramping, and inability to pass urine and stool. Superficial abscesses are characterized by a hard mass around the anus, followed by increasing pain, red and hot local skin, and severe swelling or throbbing pain after suppuration. After the abscess breaks down, the pain will be relieved and the anal fistula will be left behind. 6.Anal cancer (anal canal cancer and perianal cancer) (less common) In the early stage of anal canal cancer, there is a swelling on the anal verge or anal canal without obvious symptoms, and further development mainly shows persistent anal pain, which is aggravated after stooling, increased frequency of stool, incomplete feeling of defecation and small amount of blood in stool, similar to anal fissure and other common diseases. Therefore, for patients with anal pain, doctors should do anal finger examination after injecting dicaine slurry into the anus to exclude anal canal cancer. In the early stage, perianal cancer is a swelling with slow growth, often with discomfort and itching. With the development of the disease, a larger lump combined with ulcer formation, pain and bleeding should occur, and pathological examination should be done to make a clear diagnosis. Therefore, when you have anal pain, for the sake of you and your family, please make sure to consult a doctor as soon as possible.