Novel Classification for Douglas Fossa Obliteration in Endometriosis Based on Surgical Anatomy

Study Objective The objective of this study was to develop a novel morphological classification for Douglas fossa obliteration in endometriosis. Design Retrospective study. Setting Nippon Medical School Hospital. Patients or Participants 29 patients with endometriosis. Interventions On the basis of the recently revealed clinical knowledge of the membrane structure of the Douglas fossa and the anatomical information derived from cadaveric dissection, a hypothetical model of the normal Douglas fossa was established. This was used to examine past surgical videos (n = 29 cases) to evaluate the patterns that exist in Douglas fossa obliteration in endometriosis. Measurements and Main Results The recto–vaginal fascia that constitutes the front of the Douglas fossa has a wing-shaped structure, with the upper edge of the wing corresponding to the uterosacral ligaments (USLs). The tip of the wing is bifurcated (a λ-type structure), and the inside is connected to the rectum to form the upper part of the rectal lateral ligament. The outer side comprises the fusion surface between the peritoneum and the underlying ureterohypogastric fascia. Results The patterns of the Douglas fossa obliteration could be classified into six types: 1: normal, 2: upper peripheral lesion type, 3: lateral displacement type (right or left), 4: forward displacement type, 5: median elevation type, and 6: diffuse median elevation type (frozen pelvis); furthermore, in terms of proportions, there were 2 (7%), 8 (28%), 6 (20%), 1 (3%), 7 (24%), and 6 (21%) cases of each type, respectively. In the median elevation type, the left and right USLs and lateral ligaments were extremely shortened, the uterus and rectum were completely attached, and the Douglas fossa was completely closed. Conclusion The cases that showed complete occlusion of the Douglas fossa were either the median elevation type or the diffuse median elevation type.