Noninvasive diagnosis of endometriosis: the role of imaging and markers

Endometriosis is defined by the presence of endometrial tissue outside the uterus. This definition is based on Sampson's concept that the disease is caused by peritoneal regurgitation and implantation of viable endometrial cells in menstrual debris [1]. Consequently, the diagnosis of endometriosis is based on histologic identification of ectopic endometrial glands and stroma. Inordinate smooth muscle proliferation is also a typical component of endometriotic lesion, however [2,3]. Deep endometriosis, which is found along the outside of the mullerian tract, is characterized predominantly by fibromuscular hyperplasia and the formation of an adenomyotic nodule and microendometriomas [4,5]. On the other hand, peritoneal and ovarian endometriosis is characterized by chronic bleeding that results in the formation of hemorrhagic blisters, fibrosis, adhesions, and ovarian endometriomas. Endometriosis is further characterized by altered immune cell responses, inflammation, neoangiogenesis, and ovarian and uterine dysfunction. These observations indicate that the disease is not merely the sum of all ectopic implants but represents a fundamental disorder that affects the entire reproductive tract [6]. Clinical and basic research in endometriosis has been hampered severely by the lack of accurate noninvasive diagnostic techniques. Transvaginal ultrasonography (TVU), Magnetic Resonance Imaging (MRI), and endometrial and serum markers have the potential to facilitate the diagnosis and can be useful in the follow-up of patients. Endometriosis research has entered the postgenomic era, and powerful genomic and proteomic technology is being applied in the search for novel diagnostic and therapeutic approaches. This article explores the recent advances in imaging techniques and the development of diagnostic molecular markers of endometriosis.