Sonographic evidence of intraperitoneal fluid. An experimental study and its clinical implications

In order to evaluate the sensitivity of ultrasound to intraperitoneal fluid, such as ascites or blood, an experimental study was performed in the pig. Various amounts of fluid were injected into the peritoneal cavity to investigate distribution and diagnostic criteria in different positions. As little as 10 ml of fluid was visualized around the urinary bladder in an upright position. In the supine position, 20 ml could be detected around the bladder and 30 ml around the liver. The injection of at least 60 ml resulted in a pattern of free-floating bowel loops. The sonographic findings of fluid distribution were correlated to radiological studies. As different amounts of fluid produce characteristic sonographic patterns, an approximate estimation of the intraperitoneal fluid volume can be made.