Ultrasound has been used to determine the presence of ascites. By comparing the ultrasonic measurements with isotope dilution results, or with the actual amount found at surgery or autopsy, it has been shown that ultrasound can be used to provide an estimate of the amount of free intra-abdominal fluid. Ultrasonic determinations of ascites have been of value in determining response to therapy, both medical and surgical. They also have proved useful as an initial rapid-screening procedure in those patients suspected of having free intraperitoneal fluid, such as in cases of abdominal trauma where hemoperitoneum is suspected.
Goldberg BB, Clearfield HR, Goodman GA, Morales JO. Ultrasonic Determination of Ascites. Arch Intern Med. 1973;131(2):217-220. doi:10.1001/archinte.1973.00320080053006