Ref (type)	Population	Outcome, Interventions	Results and statistical analysis	Effect size	Favours
Adverse effects
Systematic review	384 people with chronic anal fissure 7 RCTs in this analysis	Minor flatus or faecal incontinence 4 weeks–2 years 15/191 (8%) with lateral internal sphincterotomy 7/193 (4%) with nitric oxide donors (topical glyceryl trinitrate, topical isosorbide dinitrate)	OR 0.51 95 % CI 0.22 to 1.16 P = 0.11		Not significant
Systematic review	381 people with chronic anal fissure	Headache 4 weeks–2 years 2/191 (1%) with lateral internal sphincterotomy 66/190 (35%) with nitric oxide donors (topical glyceryl trinitrate, topical isosorbide dinitrate)	OR 29.06 95 % CI 10.30 to 82.04 P <0.00001	Large effect size	lateral internal sphincterotomy
RCT 4-armed trial	160 people with chronic anal fissure	Flatus incontinence 2/40 (5%) with open lateral internal sphincterotomy 0/40 (0%) with topical glyceryl trinitrate	Not reported
RCT 4-armed trial	160 people with chronic anal fissure	Headache 0/40 (0%) with open lateral internal sphincterotomy 6/40 (15%) with topical isosorbide dinitrate	Not reported
RCT	207 people with chronic anal fissure	Moderate anal incontinence 6/102 (6%) with lateral internal sphincterotomy 0/105 (0%) with topical isosorbide dinitrate ointment	Not reported
RCT	207 people with chronic anal fissure	Headache 1 year 0/102 (0%) with lateral internal sphincterotomy 7/105 (7%) with topical isosorbide dinitrate ointment	Not reported