Whether an external opening 10 centimeters from the anal opening is an anal fistula depends on whether there is a fistula tract leading to the anus at the external opening. For patients with a gluteal fistula, there will be an external opening farther from the anus, and by examination and probing, no fistula tract leading to the anus is detected, at which point it is not an anal fistula. For patients with high complex fistulas, the external opening will be far from the anus, and in some cases it will be a semi- or full horseshoe, at which point the fistula can be examined and lead to the anus and to a high place on the tooth line. So, whether or not it is an anal fistula depends largely on whether the external fistula tract is associated with the anus. If it is not related to the anus, it is not an anal fistula. If it is related to the anus and there is a fistula that connects to the anus on examination, it is definitely an anal fistula.