In my case I ended up in the ER with severe pain one night and when they saw how hard and large my stomach was they did a CT scan, ultrasound, MRI, everything. They saw it and referred me to a specialist who performed the surgery. Since then they’ve more often than not seen cysts on my ultrasounds. Important to note I had an ultrasound only a year earlier that showed nothing (or very small cysts) and they figured it grew that quickly - from a small cyst to a grapefruit-sized one within the year. My endometriosis was not seen on an ultrasound however and only found via laparoscopic surgery after complaining about a lot of pain for a long time. It was so bad that I had scar tissue pulling my ovaries and despite that was not noticed on any of the hundreds of ultrasounds I had done over the years. For a long time actually I was referred to urologists because they thought my pain must be associated with something else like my kidneys or bladder because of the lack of anything showing up on my ultrasounds. I had to advocate for myself a lot during those years and researched the best specialists in my city who dealt with things like endometriosis and women’s health problems specifically. My doctor who performed the surgery told me it’s a common misconception that a lot of people think they don’t have it because it didn’t show up on an ultrasound only to find it during some type of surgery later.