How is adenomyosis diagnosed?

Most commonly adenomyosis is discovered incidentally when the uterus is surgically removed for other reasons. While it can be diagnosed during hysterosalpingography (HSG) where contrast dye is injected in to the uterine cavity or with pelvic ultrasound (US), magnetic resonance imaging (MRI) is the best imaging study to detect adenomyosis. In fact, US commonly mistakens adenomyosis for uterine fibroids (due to similar clinical findings, see question on signs/symptoms of adenomyosis) only to be correctly diagnosed with MRI.