A sunken fluid in the rectal fossa of the uterus is also clinically called pelvic fluid. The normal pelvic fluid is around 20mm, which is normal. Uterorectal fossa depression fluid is usually measured by ultrasonography to measure the depth of fluid accumulation, and more than 20mm is abnormal. Under normal circumstances, fluid can accumulate in the utero-rectal fossa depression, but it is not a lot and does not need to be treated clinically. If there is abdominal distension, cramping, increased leucorrhea with radiating anal pain, the effusion may be increased and treatment is needed. Normal pelvic fluid can serve to relieve bowel movements and avoid intestinal adhesions. Clinically, pelvic effusion may also consist of fluid leakage from the gastrointestinal mucosa or fluid leakage during ovulation.