Amended sample size The sample size of the study has been adjusted downward to 157 due to the loss of one of the study centers for accrual. The revised sample size considers the outcomes of diagnostic yield and sensitivity of clinical determination of identified lesions at the time of surgery, by modality. A review of the first 69 patients enrolled and assigned to the combined white light/NBI arm shows an average detection rate for any lesion to be 4.2 per patient using NBI versus 2.9 per patient with white light. The minimal detectable difference in diagnostic yield and sensitivity was determined using nQuery 6.01 (Elashoff, 2005). With the current projected sample size of 157 patients, the minimal detectable difference between the two modalities, with 90% power, in diagnostic yield proportions and sensitivity estimates is 12.2%. Thus, the power of the study remains sufficient to detect a clinically meaningful difference in detection of endometriosis by white light and NBI.