dominal girth and the protrusion index likewise rely on the The purpose of this study was to develop a method by assumptions that adipose tissue and lean mass do not which ascitic volume can be calculated using transcorchange. This study describes a new method by which ascitic poreal ultrasonography, and to determine the accuracy volume can be calculated using simple ultrasonographic meaof this method by comparison with the volume of distrisurements. bution of a radiolabeled tracer (indicator dilution technique [IDT]). Subjects with ascites confirmed by ultraso-MATERIALS AND METHODS nography were recruited from the San Francisco Patients were recruited from the San Francisco General Hospital General Hospital Gastroenterology and Liver Clinics. Liver Clinic and Gastroenterology Clinic. Patients suspected of hav-With subjects in the prone position on their hands and ing ascites on the basis of physical examination underwent transcuknees, ultrasonographic measurements were obtained taneous abdominal ultrasonography to confirm the presence of free along the ventral surface of the abdomen. The greatest intraperitoneal fluid. All patients underwent a diagnostic paracente- vertical depth of ascitic fluid was recorded, and the absis; all patients in this study had a portal hypertensive etiology of dominal circumference was measured from this point. ascites (albumin gradient Β’1.1 gm/dL). Clinical estimation of the The ascitic fluid volume was modeled as a segment of a volume of ascites was recorded by the referring physician. This esti- sphere. IDT was performed as the reference method by mate was based on weight, body habitus, and physical examination injecting 99m Tc-labeled macroalbumin into the peritowithout standardization of technique. Approval from the hospital committee for human research was obtained prior to the onset of the neal cavity and determining the volume of distribution study, and written, informed consent was obtained from each study of the indicator. Nine patients were evaluated. The meparticipant. dian volume of ascites measured by the IDT was 11.2 L Ultrasonographic Determination of Ascitic Volume. Patients were dilution techniques (IDT) were performed by different operators who California,