It is possible to do colonoscopy when anal fissure is present, and it usually does not cause too much harm, but it needs to be done under the guidance of a professional doctor. Anal fissure is usually due to improper diet, mechanical trauma and many other factors lead to fissure of the skin around the anus, due to the colonoscopy lens is thicker, improper operation, may aggravate the original condition, so you need to operate under the guidance of a professional doctor. Once a patient has an anal fissure, he should go to the hospital in time for examination and use erythromycin ointment, hemorrhoid cream and other medicines under the guidance of the doctor for treatment, and for patients with unsatisfactory effect of medication, he can take anal fissure resection and other surgical methods for treatment. Patients with anal fissure should pay attention to light diet in daily life, avoid eating too spicy and stimulating food. Keep the perianal area clean and hygienic, ensure smooth defecation, prevent constipation and diarrhea. It is recommended that patients with anal fissure should first go to a regular hospital for examination to clarify their condition and listen to the doctor’s opinion before doing colonoscopy. Do not make a blind decision on your own, so as not to damage the anus and aggravate anal fissure.