"Unfortunately, behavioral treatment for anal fissures to reduce the high muscle tone of the anal sphincter is not generally a focus of colorectal surgeons who are consulted for this problem. If you seek treatment from a colorectal surgeon, you will often end up with surgery. This approach does not take into consideration the fact that someone with a tight anal sphincter can learn to voluntarily loosen it with proper physical therapy and behavior instruction..."
In the same passage, the authors point out that while an orthopedic surgeon would cause dismay were he/she to propose cutting a patient's back muscles in order to alleviate the pain of back tension, the cutting of the anal sphincter is accepted as a normal procedure. The process of learning to relax the anal canal simply doesn't lie within the remit of conventional medicine.
It's an interesting and thought-provoking point, and makes one wonder if the difference in approach is culturally determined.