Long-term Outcomes of Botulinum Toxin Injection Into the External Anal Sphincters: An Effective New Treatment of Chronic Functional Constipation in Children

Background: Botulinum toxin (BT) is a well-recognised treatment of chronic functional constipation (FC) and soiling refractory to medical treatment. The aims of this study were to assess the short and long-term outcomes of BT injection into the external anal sphincter muscles (EAS) for chronic FC treatment.

Methods: We studied 196 children unresponsive to medical management of chronic FC, soiling, painful defecation and withholding behaviour (Rome III criteria) from April 2011 to January 2023. All patients underwent anorectal manometry (ARM) and endosonography-guided BT injection (Dysport® or Botox®) 10 units/kg body weight (maximum 200 units) into the EAS muscles at 3 and 9 o'clock positions and colonic transit study. Outcomes were measured using a validated symptom severity (SS) score questionnaire pre-operatively, at 3-6 months and 12-24 months follow up including: defecation frequency and pain, soiling, laxative(s), general health, behaviour, symptom improvement and faecaloma. Sum of scores ranged from 0 (best) to 65 (worst). We used Wilcoxon signed-rank test for matched-pairs related analysis and data presented as median (range) and p value < 0.05 was considered significant.

Results: 196 patients (104 male) with a median age of 7 (1-16) years underwent anorectal investigations and BT injection into the external anal sphincters during 12 year study period. The median short and long term follow-up was 4 (1-27) months and 16 (5-60) months, respectively. 26 (13 %) patients had autism and 14 (7.1 %) had attention deficit hyperactivity disorder (ADHD). Median anal sphincter resting pressure was of 55 (20.5-113) mmHg. The pre-operative total SS score improved from median 31/65 (4-57) before BT treatment to median 15/65 (0-49) at 4-month after BT injection and median 16/65 (0-56) at 16-month follow-up, p < 0.001. 80 % (104/130) of patients showed significant short-term and 79 % (71/90) showed long-term improvement of their chronic FC symptoms following BT injections. 9 % (18/196) children required second BT injection for symptom recurrence and 18.3 % (36/196) required formation of an antegrade colonic enema (ACE) stoma.

Conclusion: BT injection is an effective and safe new treatment of chronic FC unresponsive to conventional medical treatments. In our experience, 80 % of children have significant improvement of their symptoms and 9 % require repeat BT injection during a long term follow-up.