What causes free fluid in pouch of Douglas?

Free fluid in the pouch of Douglas, also known as the rectouterine pouch, can be caused by various conditions, including pelvic inflammatory disease, ruptured ovarian cysts, ectopic pregnancy, or trauma. It can also result from normal physiological processes, such as ovulation. In some cases, it may indicate underlying pathology, such as malignancy or advanced liver disease. Clinical evaluation and imaging are often necessary to determine the specific cause.