Patients with anal fissures are advised not to undergo colonoscopy, primarily because the procedure involves inserting the colonoscope through the anus, and anal fissures typically occur within the local sphincter muscles. The passage, or repeated movement, of the probe can cause local fissures to experience painful stimulation, or even worsen the symptoms of the fissures, increasing the likelihood of pain and bleeding for the patient afterwards. Therefore, if patients with anal fissures wish to undergo colonoscopy, they should first receive appropriate medical treatment and wait for the local fissures to heal or be completely cured before undergoing the procedure. If a colonoscopy is necessary, a lubricant can also be applied to the anal region to reduce the irritation of the colonoscope on local fissures.