Overview
Distinguish fluid, liver and spleen enlargement at the bedside, identify decompensated cirrhosis, spontaneous bacterial peritonitis, malignancy and vascular disease promptly, and use ultrasound plus diagnostic paracentesis to establish mechanism.
Ascites results from portal hypertension, malignancy, cardiac congestion, infection, pancreatic disease and less common causes. Cirrhosis is common, but anchoring on it can miss ovarian or gastrointestinal malignancy, heart failure, tuberculosis or Budd-Chiari syndrome. The first questions are whether fluid is truly present, whether the patient is unstable, and what mechanism the fluid chemistry supports. Ultrasound confirms even modest fluid, identifies a safe tap site and examines liver, spleen, portal flow and masses.
Diagnostic paracentesis should usually include cell count and differential, culture with bedside inoculation into blood-culture bottles, albumin and total protein, with cytology, amylase, triglyceride or mycobacterial tests added for specific hypotheses. A high serum-ascites albumin gradient indicates portal pressure rather than cirrhosis specifically; cardiac ascites often has high gradient and relatively high protein. A low gradient raises peritoneal malignancy, tuberculosis, pancreatitis and other peritoneal processes.