Anorectal stenosis refers to the narrowing and narrowing of the rectum or anal canal and rectum due to trauma, inflammation or congenital developmental defects, and the passage of intestinal contents is obstructed. Patients appear to have thin stools, difficulty in defecation, anal pain, or abdominal distension. A common clinical cause is improper surgery in the anus, and excessive skin removal is prone to anal stenosis. If too many points are injected in the same plane or too much injection dose is used for rectal mucosal prolapse or internal hemorrhoid injection with sclerosing agent, it can cause stricture. In addition, when anorectal tumor resection with preserved anus is performed, the anastomosis is too small, which can also cause circumferential stenosis of anorectum. The anorectal injury of traffic accident, fall injury, knife injury, war injury, strong acid, strong alkali injury, burn, scald, radiotherapy injury, etc.. Due to post-injury scar formation can cause anorectal stenosis. 3.Inflammation Clonorchiasis, intestinal tuberculosis, schistosomiasis, venereal disease, ulcerative colitis, perianal abscess, complex anal fistula, purulent sweat gland infection, amoebic enteritis, etc., can make the connective tissue of anal canal and rectum proliferate, hypertrophy, scar formation and make the anorectal stenosis. 4, congenital anorectal dysplasia During embryonic development if the paranal gap does not disappear, it will lead to congenital anal canal stenosis. As well as congenital anal atresia, if not handled properly, it often causes anal stenosis, and the developmental malformation of the sacrococcygeal bone compresses the anal canal rectum causing anal canal rectal stenosis. 5, tumor and mass compression Commonly, anal canal and rectal cancer, rectal smooth muscle sarcoma, rectal giant polyps, vaginal and uterine tumors, prostate cancer, lymphoma, chordoma, presacral spinal membrane bulge, presacral cyst, sacrococcygeal teratoma, etc. can cause anorectal stenosis. (b) Classification of anorectal stenosis 1. congenital and secondary stenosis according to medical history 2. According to the pathological nature, benign and malignant strictures are classified. 3. According to the morphology, partial stenosis, annular stenosis and tubular stenosis are classified. (1) Partial stenosis: The stenosis involves only a part of the anus, anal canal or rectum, and is flap-shaped or semi-annular, not forming an annulus. It is more common that the stool becomes thin and the stenosis can still pass a sign finger. (2) Annular stenosis: the stenosis is annular involving the anus, anal canal or rectum for 1 week, with a longitudinal length <2 cm, more common. (3) Tubular stenosis: the stenosis constitutes a circle with a longitudinal length > 2 cm, which is less common. (4) According to the degree of stenosis, Nilson proposed that it is more reasonable to grade under anesthesia, and it is divided into the following 3 degrees: (1) Mild: soft stool can be expelled, but it requires forceful rejection of the stool before it can be expelled. The finger or medium Hill-Ferguson retractor can still be inserted. (2) Moderate: difficult to pass stool, sometimes thin stool or gas cannot be controlled. The patient’s pain is obvious. (3) Severe: both defecation and exhaustion are difficult, and there is pseudo-anal incontinence and perianal dampness. The small finger or small Hill-Ferguson retractor can only be inserted by force, or cannot be inserted. Clinical manifestations 1, defecation difficulties stool thinning Due to the exit channel becomes smaller, fecal passage is blocked, patients often report defecation difficulties, because the feces is not easy to discharge. Often increase the force to reject the stool, but the expelled stool becomes thin, deformed or with grooves, or stool with blood. 2.Anal drop and pain Because of the feces moving down to the rectum can not be smoothly discharged, coupled with anorectal inflammation, so there is a feeling of anal drop. Anal pain and blood in the stool may occur due to excessive forcefulness of the feces, as well as inflammation and other factors. 3, pseudo-anal incontinence and moisture Anorectal stenosis, excessive fecal retention in the rectum, excessive pressure makes feces out of the anus, that is, the so-called pseudo-anal incontinence. Stenosis caused by anorectal scar, due to the scar, the anus or rectum can neither be effectively expanded nor completely closed, often there is involuntary flow of fecal water out of the anus and cause anal dampness, such as prolonged perianal skin can appear eczema-like changes, itching, pain, some may occur erosion and ulcers. 4, abdominal distension, abdominal pain Abdominal distension and abdominal pain can appear when heavy, such as nausea, vomiting and other manifestations of chronic incomplete intestinal obstruction, the symptoms are relieved after defecation, but the above symptoms appear again after a few days or tens of days. This symptom mostly occurs in patients with more serious rectal strictures, and the duration of the disease is mostly longer, because rectal strictures are not as easy to diagnose as anal strictures. The feces above the stricture, due to the long stay in the intestinal cavity, ferments and produces too much gas by the action of E. coli, further aggravating the symptoms of intestinal obstruction by abdominal distention. Examination: In some cases, intestinal pattern and peristaltic waves are visible in the abdomen. In some cases, cathartic agents are mistakenly taken due to difficulty in fecal evacuation. It causes intestinal movement to strengthen and induces intestinal obstruction. The diagnosis of anorectal stenosis can be made based on medical history, clinical manifestations and local examination. However, it is necessary to know whether the patient has congenital anorectal diseases, anorectal inflammation and history of trauma or surgery. Patients with anorectal stenosis often present with difficulty in fecal evacuation, constipation, thinning of stool, and moist anus; those with severe stenosis may show symptoms of incomplete intestinal obstruction such as abdominal pain, bloating, nausea, and vomiting. Rectal palpation may palpate the narrowed anus, anal canal or rectum, indicating that the finger cannot pass through, and a stiff scar with poor elasticity or inelasticity may be locally retrieved. Endoscopy reveals a narrow intestinal lumen and scar. Patients whose fingers and endoscopy cannot pass through the stricture should undergo barium enema or iodine oil enema to understand the extent, degree and morphology of the stricture. If the stenosis is circumferential, the X-ray will show a dumbbell shape, if the stenosis is tubular, it will show a funnel shape, and if the stenosis is flap-shaped, it will show a defect. For stenosis caused by compression of rectal mucosa and extra-anal skin masses, ultrasound examination of the anal canal or rectum can be performed to identify whether the stenosis is cystic or substantial, or in some cases, benign or malignant, as well as the depth and extent of mass infiltration into the intestinal wall. If the stenosis is suspected to be caused by tumor, biopsy should be performed. Biopsy is very important to determine the stenosis caused by benign and malignant tumors, and should be taken seriously. Generally, benign strictures are mostly circumferential, hard and smooth locally, while strictures due to tumors are generally irregular, with mucosal destruction, ulcer formation, brittle tissue texture, and blood in the fingertips. Serum syphilis test and condensation set test should be done for suspected STD. For suspected specific infections such as amoebic dysentery, bacillary dysentery, tuberculosis, schistosomiasis, etc., smear, bacterial culture and biopsy should be performed. V. Differential diagnosis Anorectal stenosis should first be identified as benign or malignant stenosis, congenital or as a complication or sequel of a disease or trauma. In general, congenital anorectal stenosis is most often seen in newborns; inflammatory diseases have a history of diarrhea and mucus and bloody stools; infections in the anus have a history of perianal pain, pus flow, fever and other perianal infections; trauma or surgery has a history of trauma or surgery, and it is generally not difficult to distinguish those with a clear history of the above. Chronic diarrhea and venereal lymphogranuloma, etc. 1, rectal cancer The stenosis caused by rectal cancer is progressively more difficult to defecate, with blood stool or mucus stool, increased frequency of stool, and anal drop feeling. The above symptoms of early rectal cancer are not obvious, and symptoms such as blood in stool may appear occasionally. Therefore, rectal cancer causing rectal stricture is mostly in advanced stage. For distal rectal cancer, generally a lump can be found through rectal finger diagnosis, which is uneven and moderately hard in texture, and the lump invades the intestinal wall for 1 week or almost 1 week, and the finger sleeve is full of mucus and blood. Cancer of proximal rectum can be detected by sigmoidoscopy and fiberoptic colonoscopy, which can reveal unevenness, erosion, bleeding, brittle texture and easy bleeding when touched, and the tumor can invade the intestinal wall for 1 week or 4/5 weeks with different circumference, and the intestinal cavity is narrow and the mirror cannot pass through. The recurrence of anastomotic cancer after rectal cancer surgery and stenosis due to small anastomosis should be differentiated. In the former case, the anastomosis of rectal finger examination can mostly reveal masses or ulcers and blood in the finger sleeve. In the latter case, although the anastomosis is small, the scar of the anastomosis is uniform for one week, and there is mild stiffness but no mass, which can be distinguished by biopsy or CT examination. 2, inflammatory bowel disease inflammatory bowel disease refers to ulcerative colitis and clonorchiasis, both can appear abdominal pain, diarrhea, mucus and blood stool, fever and other clinical manifestations, can cause intestinal lumen narrowing or internal fistula, the main points of differentiation are as follows: (1) ulcerative colitis: lesions invade the rectum and left hemicolectomy, some patients lesions invade the whole colon, lesions are continuous damage. In the acute stage, the mucosa is congested, edematous, the mucosal vascular texture is unclear, there are dense, small superficial ulcers, and the ulcers are mostly 0.1 to 0.3 cm in diameter. In severe cases, the intestinal mucosa is extensively eroded, bleeding, dense superficial ulcers, brittle mucosal texture, and a large amount of blood and mucus in the intestinal lumen. A large number of polyps and a large number of scars can be formed during the healing process of ulcerative colitis leading to rectal stricture. (2) Clonorchiasis: The disease mainly damages the entire gastrointestinal tract from the oral cavity to the rectum, the lesions are jumping, segmental damage, sometimes 2 to 3 longitudinal ulcers are seen side by side, some ulcers exist longitudinally and horizontally, the edge of the ulcer is proliferated with a large amount of granulation tissue, and the general view is cobblestone pavement sign. The stenosis is formed due to hyperplasia, fibrosis and scar formation at the lesion site. 1/4 of the cases of clonorchiasis form intestinal stenosis. the disease invades the rectum mostly above the dentate line, a few involve the anal canal, this stenosis is mostly tubular, the stenosis is accompanied by abscess or anal fistula, the possibility of clonorchiasis should be highly valued. (3) Venereal disease: mainly venereal lymphogranuloma is more common in women with a history of impure intercourse. The lesions invade the genitals, rectum and inguinal lymph nodes with viral infection. Patients have fecal difficulties, urgency, and pus and blood stools. The lesions are mostly located above the dentate line, with a tubular stenosis, hard texture, smooth surface, pale color, and an open anal opening. Positive serum condensation set test and Freire test. (4) Intestinal tuberculosis: Intestinal tuberculosis is more common in the ileocecal region of the colon, but a few intestinal tuberculosis also invades the rectum and anal canal. Proliferative intestinal tuberculosis causes narrowing of the intestinal canal due to extreme proliferation of tuberculosis granulation tissue and the formation of huge masses. Ulcerated intestinal tuberculosis with mucosal adhesions can pull or compress the intestinal canal to form stenosis; ulcer healing, fibrous tissue proliferation, and scar formation can also narrow the intestinal canal. Examination: Tuberculous granulation tissue has edema, erosion, bleeding, and brittle texture, which is difficult to distinguish from the granulation tissue of clonal disease in general, so it should be biopsied for pathological diagnosis. However, in addition to diarrhea, patients with intestinal tuberculosis also show dampness, night sweats, and emaciation, and anti-tuberculosis treatment is effective. Most of the patients with anorectal stenosis are caused by trauma or surgery, so it is extremely important to prevent anorectal stenosis when performing anorectal surgery. For example, when performing surgery such as hemorrhoidectomy, excessive removal of anal skin should be avoided, and when anastomosis of intestinal segments with the anal canal or rectum, the choice of anastomosis should be appropriate and not too small to prevent anastomotic stenosis. Treatment of anorectal stenosis should be based on different stenoses of benign and malignant nature, and different treatment plans should be adopted. If the stenosis is caused by malignant tumor, tumor resection or radical surgery, or radiotherapy or chemotherapy should be performed. If the tumor cannot be resected, the stenosis cannot be released, and the stenosis is complicated by intestinal obstruction, treatment such as proximal colostomy of obstruction should be performed. The treatment of benign anorectal stenosis is mainly the following methods: 1. Conservative treatment (1) Balloon dilation method: Applicable to circumferential stenosis of the rectum, this method is easy to grasp and effective. After seeing the stenosis cavity through fiberoptic sigmoidoscope or fiberoptic colonoscope, the balloon controller is inserted from the biopsy tube of the mirror, the dilator is passed through the narrow intestinal cavity, the middle of the balloon of the dilator is placed at the annular stenosis, and then the balloon is inflated into the balloon through the balloon connecting tube, and the balloon expands to dilate the narrow intestinal tube. The dilatation lasts for 10-15 minutes, then the gas in the balloon is withdrawn and the dilator and fiberoptic enteroscope are withdrawn. (2) Finger and metal instrument dilation method: applicable to the distal end of the anal canal and rectum. This method is simple and easy to use. However, the operation should be gentle and prevent rough expansion to prevent perforation and tearing of the anal canal. Dilation time is the same as before. (3) Physiotherapy: local electrotherapy and heat therapy can soften the scar and make the stenosis dilate. During the treatment with the above method, patients should eat more food containing high fiber, because the formed stool has the effect of dilating the anus, in order to maintain the effect of mechanical dilation and physiotherapy. 2.Surgical treatment is suitable for patients with benign anorectal stenosis. Pre-operative bowel preparation is the same as that for general colon and rectal surgery. (1) Longitudinal incision and transverse suture: for patients with partial and circumferential anal stenosis not exceeding 2 cm and distal rectal circumferential stenosis. (2) Y-V anoplasty: for semi-annular stenosis with scar below the dentate line or anal canal with annular stenosis. (3)V-Y flap anal canalplasty: for patients with canalicular stenosis. (4) S-shaped flap anal canaloplasty: for larger circumferential stenosis of the anal canal. (5) Z-flap anal canaloplasty: for patients with light scarring of anal canal circumferential stenosis. (6) Trans-sacro-caudal rectal stenosis with longitudinal incision and transverse suture: for patients with middle and upper rectal stenosis. (7) Transabdominal rectal stenosis resection: for patients with upper or middle and lower rectal stenosis who have failed the above treatments. Postoperative treatment: In order to avoid or reduce the infection of the postoperative incision, generally fast for 3 days after surgery, infusion, application of antibiotics and symptomatic treatment, such as thin stools, the number of times available compound camphor tincture 5ml 1 to 2 times a day. 3 days later into the liquid diet. The stitches are removed in 1 week. 10 days later, dilatation is started, once a day or 2 – 3 times a day until healed.