I experienced an anal fissure in September 2012 - I was off work for about 6 weeks. No idea how it came about because I did not experience constipation AT ALL. I received treatment with rectogesic at least 4 times during 12 months. But it was in autumn 2013 (12 months later) that we figured out it was purely a dermatological problem.
I go to the gym a lot and the track pants I wore was irritating my skin. Amongst other issues, I was very careless about what clothes I wore in terms of material (but who wouldn't be?). I never thought it would be something like this! Anyway, the situation is now as of 2014, I resolved the reoccurrence of the fissure, by treating the skin around the anus and generally my bottom. Keeping it moisturised and wearing the cotton based material wherever possible. I add Anusol cream to my daily regime (after bowel movement only) vaseline & an ointment called Polyfax (by GSK) only at night - I also keep my stools soft. And now I am fissure free!!
So bottom (excuse the pun) line - get a dermatological examination too.
Also I have 3 new sealed tubes of Diltiazem that I no longer require if anyone is interested !!