The classification of endometriosis: historical evolution, critical review and present state of the art.

The surprising disagreement in treatment results obtained by the various authors treating endometriosis is in large part due to differences in the severity of the disease. Only the adoption of a satisfactory staging system allows valid comparison between homogeneous groups of patients. This paper reviews and analyzes the various classifications proposed with the aim of showing the original aspects and the defects that led to the development of new systems including the most recent one published by the American Fertility Society. Devising a classification system presents unexpectedly great problems, but it is essential to be able to compare treatment results.