Brief Answer:
Surgery can be most effective treatment.

Detailed Answer:
Hello dear welcome to Ask a doctor's service.
I read your query and here is my advice.

The treatment of an anal fissure depends on the time you have been dealing with it.
If if is first time happening you can use frequent wash with warm water for weeks also you can use nitroglycerin ointment to help sphincter relaxation and increase blood flow to help healing.
If you have tried all these methods and you are chronically dealing with anal fissure you can consider surgery as most effective treatment.

Hope I have answered the question.
Let me know if I can assist you further.

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