If an anal fissure consistently fails to heal proactively, it may be due to the repeated expansion of the fissure, or recurrent instances of dry stools and bleeding, leading to ulcerative, infectious changes at the local fissure. This can progress into a chronic anal fissure. Chronic anal fissures have larger local wound surfaces, and the patient may also experience excessive tightness in the anal canal. The local fissure, wrapped within the tightened anal canal, does not drain well, making self-healing impossible. To treat chronic anal fissures, or recurrent fissures, it is recommended to perform a lateral internal sphincterotomy and further debride the local fissure to ensure complete healing of the anal fissure.