The aim of this study was to identify the relation of the duration of anal fissure with the level of Endothelin-1 (ET-1), which appears to be an interesting and somewhat weird study subject. Because there is little theory on the etiology of the chronic anal fissure, we assume that we can get some informative ideas from this study. ET-1 is a peptide, which is known to be a strong and continuous vasoconstrictor, and an ET-1 receptor antagonist (bosentan®) has been developed to treat pulmonary hypertension [1-4].

This study has some limitations: 1) The level of blood ET-1 could reflect the action of ET-1 on anal tissue? 2) ET-1 may not be enough to explain the various etiologies of anal fissure? 3) There are no discussions of other factors that can influence the level of ET-1. Conclusively, this study does not strongly support a relationship between ET-1 and chronic anal fissure. Further detailed studies regarding the characteristics associated with ET-1 may helpful to identify one of the etiologies of chronic anal fissure.