<prompt> Best investigation endometriosis is :LaparoscopyUSGX-ray pelvisCT Scan  <response>: Laparoscopy is the gold standard in the diagnosis of endometriosis. The diagnosis should be validated by peritoneal and tissue biopsy, because corpus luteal haematoma can resemble a chocolate cyst. Reference: Shaws Textbook of Gynaecology 16th edition page no 415 