This might be useful:
"Can you diagnose Endometriosis via Ultrasound?
September 3, 2016
Dr Sofie Piessens, Endometriosis Australia's Medical Advisory Committee
The ability to diagnose deep infiltrating endometriosis with transvaginal ultrasound has improved dramatically around the world since 2009.
What can the ultrasound diagnose?
Endometriosis is defined as the presence of tissue similar to that of the lining of the uterus (endometrium) outside of the uterus, most commonly on and below the ovaries, and deep in the pelvis behind the uterus, called the Pouch of Douglas. Here, the endometriosis grows on the ligaments behind the uterus and on the vagina and rectum. It also may grow on the bladder, appendix, and even sometimes in the upper abdomen or in the abdominal wall in the scars of a laparoscopy or caesarean delivery.
There are many presentations of endometriosis which may be identified by the surgeon at laparoscopy. A distinction is made between superficial lesions and deep infiltrating endometriosis.
In the majority of women with endometriosis the endometriosis found in the pelvis has only implanted superficially. Superficial lesions of endometriosis can never be diagnosed on ultrasound as they have no real mass, only colour, which cannot be detected with ultrasound. These lesions can cause as much pain as some deep infiltrating lesions but they can only be seen on laparoscopy. They may be removed during a laparoscopy and special preoperative measures are rarely required."
My bolding - superficial lesions can't be found by ultrasound but can still cause as much pain - go back and ask to be checked again. Ultrasound isn't enough.