What is an anal fissure? In clinical practice, we often encounter patients asking this question. An anal fissure is a crack in the skin around the anal canal; simply put, it is a split in the skin at the anus. The direction of the split aligns with the direction of the anal skin's folds. Of course, not all cracks in the anal skin are called anal fissures. It is only considered an anal fissure if there is a full-thickness split in the skin at the anus. If it is a superficial skin split, it is referred to as an anal skin laceration or fissuring, such as those caused by certain anal itching diseases, which are in fact fissures in the anal skin. Anal fissures commonly occur at the “anterior and posterior midline” of the anus, which is similar to the directions of 6 o'clock and 12 o'clock as described on a clock face. Doctors often describe these as positions at 6 o'clock and 12 o'clock.