**4. Diagnostic modalities for evaluation of endometriosis**

The diagnosis of endometriosis is conventionally made by laparoscopy but over the time the imaging techniques have evolved to greatly facilitate the pre operative diagnosis. Further laparoscopy has limited role in visualizing atypical non pigmented extraperitoneal sites of involvement and the areas especially concealed by pelvic adhesions.

By and large ultrasound is the first preliminary investigation done to assess the pelvic disease in reproductive age group. Although it has limited role in detection of superficial implants, it is useful in the diagnosis and treatment of endometriomas. MRI provides a good alternative with high specificity and sensitivity for detecting deep infiltrating (DIE) endometriosis as well as endometriomas. The main drawback of MRI is again inability to detect small peritoneal infiltrates (< 3mm). Introduction of fat saturated T1 weighted image on MRI has consistently improved its accuracy in distinguishing between ovarian mass with lipids from endometriomas.

Computed tomography usually gives ill defined results, thus is not very helpful. Conventional investigations like barium enema or intravenous urography may prove useful in detection of visceral endometriosis. Their use however is limited in current practice due to excessive radiation dose.

Further sections of this chapter will first discuss the various imaging modalities in detail followed by the characteristic appearance of diverse typical and atypical forms of endometriosis.
