I've been dealing with an anal fissure since 9/2010 and had surgery 3/2011 but still haven't been able to say I'm fully cured. I had kidney stones in 7/2011 and my kidney MD discovered that I had parathyroid issues. These glands control calcium in your blood. I had surgery to remove one of these glands that had a tumor in it last week. Surgery wasn't that bad, but it threw off my BMs which caused some bleeding from fissure, which had been almost healed. But what I realized is that one symptom of having too much calcium in your blood is that it triggers muscle spasms. And the main cause of a chronic anal fissure seems to be spasms in the anal muscles that won't allow the fissure to heal. So I'm thinking that in my case, I developed chronic fissures because of my parathyroid issues and the only reason I caught this was that I developed kidney stones. In fact, I might not have needed the anal fissure surgery if other doctors had caught this.
Bottom line advice: if you have a chronic anal fissure, have your blood calcium checked and if it's high, ask for a check of your Parathyroid hormones. If those are high, you might have found the solution for your fissure. Definitely get that taken care before you have anal fissure surgery as the added hormones cause your calcium to be leeched out of your bones, causing osteoporosis.