The goal of this clinical trial is to evaluate the efficacy of botulinum toxin injection in treatment of patients with chronic anal fissures comparing between two doses of botulinum toxin injection focusing on healing rate, fissure pain, incontinence and return to daily activity. patients will be divided into two groups group A) will receive 50IU from Botulinium toxin type A in the form of two injections at 3 o'clock and 9 o'clock without any anasthesia. While group B) will receive low dose injection in the form of 20IU by the same technique.

Background: Severe anal pain and a lower quality of life are two consequences of chronic anal fissure (CAF). The ideal dosage for botulinum toxin type A (BoNT-A), a sphincter-preserving substitute for lateral internal sphincterotomy, is still unknown. In this study, fixed-site 20 U and 50 U onabotulinumtoxinA regimens were compared using a structured 1-year follow-up and a standard injection technique at 3 and 9 o'clock.

Aim of the study:The aim of the work is to evaluate the efficacy of botulinum toxin injection in treatment of patients with chronic anal fissures comparing between two doses of botulinum toxin injection focusing on healing rate, fissure pain, incontinence and return to daily activity Methods: OnabotulinumtoxinA 20 U (10 U per site) or 50 U (25 U per site) were randomly assigned to 70 adults with CAF who were refractory to at least 8 weeks of medical therapy in this prospective, randomized, double-blind, parallel-group trial. At eight weeks, complete clinical fissure healing was the main result. Pain and bleeding response, healing time, recurrence following initial healing, temporary flatus incontinence, and the need for surgery during a one-year follow-up were secondary outcomes. Recurrent and persistent non-healing cases went straight to surgery instead of another injection.

Inclusion Criteria:

• Participants were required to have persistent symptoms despite standard first-line management.

Exclusion Criteria:

Exclusion criteria included atypical fissure location or appearance, such as lateral or multiple fissures; suspected secondary causes, including Crohn's disease, infection, tuberculosis, HIV-related ulceration, or malignancy; the presence of a perianal fistula or abscess; and contraindications or high-risk conditions for botulinum toxin treatment, including pregnancy, breastfeeding, known hypersensitivity to botulinum toxin products, active infection at the injection site, or significant neuromuscular junction disorders.

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