Free fluid refers to liquid that is not contained within an organ or cyst but flows freely within a body cavity. On ultrasound, free fluid appears as anechoic areas that conform to the spaces between organs and shift with changes in patient position. In the abdomen, free fluid typically collects first in the dependent areas: Morrison’s pouch between the liver and right kidney, the splenorenal recess between the spleen and left kidney, and the pelvic cul-de-sac behind the uterus or bladder. Small amounts of free pelvic fluid can be normal in women of reproductive age, especially after ovulation, but large amounts or fluid in unusual locations can indicate ascites, hemorrhage, ruptured cyst, or ectopic pregnancy.
Sonography Term