Original article
Botulinum toxin improves pain in chronic anal fissure
Hugo Amorim, , José Santoalha, Rui Cadilha, Maria-José Festas, Paula Barbosa, Armanda Gomes
Centro Hospitalar de São João, Porto, Portugal
Received 21 January 2017, Accepted 20 April 2017

Chronic anal fissure is a common condition associated with intense pain. Local botulinum toxin injection is a valid option in its management. The purpose of this study was to evaluate the efficacy of botulinum toxin on pain relief in chronic anal fissure patients.


We conducted a retrospective cohort study, involving 81 consecutive patients referred to a chronic pain management unit due to a chronic anal fissure for treatment with botulinum toxin, during a 4 year period. Data were collected from hospital records regarding pre-treatment and post-treatment pain (numeric rating scale), side effects, need for botulinum toxin reinjection and need for surgical treatment. We used standard statistical methods for inter (t-test and qui2) and intra-group (paired sample t-test) comparisons, according to variables distribution.


Pain intensity rest score significantly improved after BoNT injection [variation: −4.2±2.9 (p<0.001)], as did pain post-defecation score [variation: −5.1±3.0 (p<0.001)]. 8.6% needed botulinum toxin reinjection and 23.5% were submitted to surgery. Side effects were reported in 8.6%.


The efficacy of botulinum toxin use on pain reduction along with its non-permanent and minor side effects support its role in the resolution of chronic anal fissure. However, treatment failure in the long term is still significant.


Botulinum toxin is effective on pain relief in patients with chronic anal fissure, which supports its inclusion in the management algorithm of this condition.

Botulinum toxins, Pain, Fissure in Ano

Open Access

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Porto Biomedical Journal is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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