Characterization and quantification of fluid in the abdomen by ultrasound and magnetic resonance imaging in children with clinical suspicion of appendicitis.

Purpose: While regarded as a secondary sign of pediatric appendicitis, the frequency of physiologic intra-abdominal fluid in children with suspected but absent appendicitis is unknown. Ex vivo: to assess the validity of US/MRI measurements of free fluid. In vivo: in suspected pediatric appendicitis, to assess the amount of abdominal fluid by US and MRI, determine performance characteristics of US in fluid detection and identify fluid volume ranges in confirmed appendicitis.