[Light and scanning electron microscopy study of the pathogenesis of pilonidal sinus and anal fistula].

From various theories about the development of the pilonidal sinus Stelzner's opinion as to an acquired disease is generally accepted. Our scanning electron microscopic investigations strengthen this theory that hair splits and drills into the skin. Hooks keep it from retracting. Needlelike sharp ends may contribute to the hair piercing the skin. The anal fistula differs from the pilonidal sinus concerning morphology and pathogenesis. Surgical treatment must consider the localisation of the proctodeal gland.