Currently no laboratory tests or diagnostic imaging exist that can be reliably used to diagnose endometriosis. Ultrasound, computed tomography, and magnetic resonance imaging are generally not effective unless ureteral, bladder, or bowel involvement is suspected. Ultrasonography may be effective in visualizing endometriomas of the ovaries, but it is overall a poor diagnostic tool. Cancer antigen 125 (CA-125) blood levels may be elevated with endometriosis, with the best correlation seen in women with more severe disease (by staging).