Sensitivity of transabdominal ultrasonography in detection of intraperitoneal fluid in humans

The sensitivity and specificity of ultrasonography in detection of free int raperitoneal, fluid is over 90%. The lowest detectable volume of free fluid in humans is unknown. The distribution of intraperitoneal fluid was studie d in 86 patients by transabdominal US in group A (n = 21, 10 ml of fluid), in group B (n = 15, 50 ml of fluid) and group C (n = 50, splenic trauma). U ltrasound detected fluid in 15 of 21 patients in group A, and in all patien ts in groups B and C. In group A 10 mi of fluid was found in 71% of cases b ehind the bladder, and in only 5-14% of cases in the upper abdomen. In grou p B 50 mi of fluid was found in all patients in the lower pelvis, but in on ly 20% in Morison's pouch and in 7% around the spleen. In group C 200-4500 mi of fluid was detected by US in 72% of patients in the perisplenic space, in 60% in Morison's pouch and in 42% in the retrovesical space. Small volu mes of free intraperitoneal fluid (10-50 mi) can be detected with current U S scanners, but only near the site of injury. These results support the rol e of US as a primary imaging modality in abdominal trauma.