We appreciate the comments of Dr Roger McMaster-Fay regarding pelvic congestion syndrome and immunohistochemistry to demonstrate endometriosis when histology is unremarkable. However, we do not believe that the issues raised cast doubt on the findings in our study. Furthermore, the comments of Dr McMaster-Fay illustrate a failure to recognize the challenges of gathering data from 52 hospitals ranging from large academic tertiary hospitals to small community hospitals.

First, we do not consider pelvic congestion syndrome separately from chronic pelvic pain because there is ambiguity in the differential diagnosis. The surgical and imaging criteria to establish abnormal adnexal vascularity consistent with pelvic congestion are not well established. This leads to ambiguity for clinicians, and we could not expect clinicians across the collaborative spectrum to be consistent in differentiating the 2 conditions.

Second, immunohistochemistry protocols for negative histology were neither included within our 52 hospital collaborative nor are they a feasible goal for the future. Techniques such as CD10 immunohistochemistry are not yet a routine part of analyzing specimens for endometriosis. It would not be possible to expect every hospital and every pathologist, regardless of bed size or affiliation, to explore these protocols to account for negative pathology.

In summary, data from Michigan Surgical Quality Collaborative are a reflection of clinical practice, not research-driven inquiry. There are limitations to the current knowledge and to standard techniques. Nonetheless, we believe that our study identifies areas of clinical practice worthy of attention for quality improvement.