Ascites: Symptoms, Signs and Diagnosis
Nonspecific abdominal discomfort and dyspnea may occur with massive ascites, but lesser amounts are usually asymptomatic. The diagnosis is made clinically by detecting shifting dullness on abdominal percussion, though US or CT scan can detect much smaller amounts of fluid. In advanced cases the belly is taut, the umbilicus is flat or everted, and a fluid wave can be elicited. Differentiation from obesity, gaseous distention, pregnancy, or ovarian tumors and other intra-abdominal masses usually is easily made by clinical examination, but scanning techniques or diagnostic paracentesis may occasionally be required. In liver disease or in intra-abdominal disorders, ascites is usually isolated or out of proportion to peripheral edema; in systemic disease, the reverse is usually true.
If the cause is uncertain, a diagnostic paracentesis should be done. From 50 to 100 mL of fluid is removed and, as clinically indicated, is assessed for gross appearance, protein content, blood cells, cytology, culture, acid-fast stain, and/or amylase. In most disorders the fluid is clear and straw-colored. Turbidity and a high polymorphonuclear cell count (300 to 500 cells/µL) suggest infection, while sanguineous fluid usually signals neoplasm or TB. The rare milky (chylous) ascites is most common with lymphoma. A protein concentration of 3 gm/dL favors liver disease or a systemic disorder; a higher protein content suggests an exudative cause (eg, tumor or infection). However, ascitic protein in cirrhosis occasionally is 4 gm/dL; a serum to ascites albumin concentration gradient 1.1 gm/dL more reliably indicates portal hypertensive ascites than does the total protein content of the fluid.
Cirrhotic ascites, especially in alcoholics, occasionally becomes infected without an apparent source (“spontaneous bacterial peritonitis”). Clinical diagnosis may be difficult, as the fluid masks signs of peritonitis. Thus, early diagnostic paracentesis and culture should be done in cirrhotics with unexplained deterioration and fever, especially if abdominal discomfort is present; presence of 300 to 500 polymorphonuclear cells/µL of fluid justifies therapy. Survival depends on early, vigorous antibiotic therapy.