Transvaginal ultrasonography of rectal endometriosis

Objectives: The aim of this present study was to evaluate the interobserver variation of transvaginal ultrasonographic measurements of endometriosis infiltrating the rectosigmoid wall. Methods: Transvaginal ultrasonography was performed independently by two observers. Observer 1 had several years of experience in ultrasonography while observer 2 was a medical student with no prior experience in ultrasonography or endometriosis. In 24 patient length, width and depth of endometriosis infiltrating the rectosigmoid bowel was measured. The differences between the observers were analysed by Bland and Altman plots with 95 % limits of agreement. Results: No systematic differences were found between the observers. Probabilities for differences to be within 30 % of the mean were 0.81, 0.63 and 0.61 for the length, width and depth respectively. Ninety-five percent limits of agreement were 0.64 -1.87, 0.54 - 1.69 and 0.56 - 1.87 for the length, width and depth respectivelyConclusions: We found no systematic differences between a routined and an untrained observer regarding estimation of size of endometriotic lesions in the rectal wall. This indicates that systematic training in transvaginal ultrasonography for a relatively short period gives comparable scanning results between the two observers. It seems that transvaginal ultrasound could be used as a diagnostic tool for rectal endometriosis in most departments. However, the irregular morphology of the lesions makes the measurements very complex, and a strict standardized protocol is needed.