Routine complete blood count (CBC), basic metabolic profile, liver enzymes and coagulation tests should be performed. Most experts recommend a diagnostic paracentesis be performed if the ascites is new or if the patient with ascites is being admitted to the hospital. The fluid is then reviewed for its gross appearance, protein level, albumin and cell counts (red and white).
The Serum-Ascites Albumin Gradient (SAAG) is probably a better discriminant than older measures for the causes of ascites. A high gradient (> 1.1 g/dL) indicates the ascites is due to portal hypertension. A low gradient (< 1.1 g/dL) indicates ascites of non-portal hypertensive cause.
Ultrasound is often performed prior to attempts to remove fluid from the abdomen. This may reveal the size and shape of the abdominal organs. Doppler studies may show the direction of flow in the portal vein, as well as detecting blockage of the hepatic vein (Budd-Chiari syndrome or Portal Vein Thrombosis--PVT). Additionally, the sonographer can make an estimation of the amount of ascitic fluid. Difficult-to-drain ascites may be drained under ultrasound guidance. An abdominal CT scan is a more accurate alternate than ultrasound to reveal abdominal organ structure and morphology.