This is the case of a child with dysuria and pelvic pain. What is your diagnosis based on these images? Choose from the following:

There is a large purulent fluid collection with echogenic material posterior to the uterus. The cause of the abscess is severe acute appendicitis. Appendicitis must always be considered as one of the possible causes in cases of pelvic pain with an echogenic collection in the pelvis. In this case the other pelvic structures, including the uterus and the ovaries, were normal. A large echogenic collection may also mimic a pelvic mass.