PurposeMany kinds of substances are produced on vascular endothelial activation. The aim of this study is to confirm an increase in Endothelin-1 (ET-1), the most potent vasoconstrictor, which is produced by endothelial activation, in patients with chronic anal fissure and to infer the relationship between ET-1 and anal fissure chronicity.MethodsThe study groups are divided into three different groups with 30 subjects each. Group 1 is comprised of healthy volunteers, group 2 of chronic anal fissure patients, and Group 3 of patients with higher than 3rd degree hemorrhoids. Blood samples were taken to measure the ET-1 levels in subject's serum and to compare the results with those for the control groups.ResultsAmong the 90 subjects, 38 were male, and 52 were female. The average age was 36.8. The average ET-1 level marked 1.47 ± 0.78 pg/mL for male subjects and 1.16 ± 0.47 pg/mL for female subjects (P = 0.02). The average ET-1 level in the patient groups is as follow: 1.21 ± 0.44 pg/mL in group 1, 1.46 ± 0.83 pg/mL in group 2, and 1.20 ± 0.56 pg/mL in group 3 (P = 0.14).ConclusionGroup 2, the chronic anal fissure patient group, showed a higher ET-1 level than groups 1 and 3, the control group and the hemorrhoid patient group, but this difference had no statistical significance.