Uterorectal fossa effusion is also known as fluid found in the pelvic cavity and most of the time there is no fluid in the uterine rectal fossa. If fluid is present there are two possibilities to consider, one is physiological and the other is pathological. Physiological uterine rectal fossa fluid is mostly seen around ovulation or around the onset of menstruation when there is a small amount of fluid, not more than 1cm, and there is no abdominal pain or bloating, which is a normal physiological phenomenon, not a disease, and does not need to be treated. If it is a hemorrhagic fluid, it should be considered that there is an accumulation of blood inside the rectal fossa caused by intra-abdominal bleeding. If it is pus it may be pelvic pus, such as severe tubal necrosis with pus flowing to the lowest location of the uterine rectal fossa to form a collection of fluid. Most cases of fluid accumulation in the utero-rectal fossa may be exudative fluid, but the amount is more than 1cm or even 2-3cm, accompanied by abdominal pain and abdominal distension, which is mostly seen in women with chronic pelvic inflammatory diseases.