Prompt paracentesis before starting antibiotics is ideal
Send fluid for analysis and two 10ml vials (aerobic and anaerobic) for culture and sensitivity
Rule out secondary peritonitis from a perforated viscus (2 of total protein > 10 g/L, glucose < 2.8 mmol/L, LDH > ULN for serum is a strong predictor for secondary peritonitis, as is polymicrobial infection)
Start empiric antibiotics if one or more of:
Otherwise, it is reasonable to wait for ascitic fluid analysis, and starting antibiotics if PMN count is ≥ 250 cells/uL
Also treat symptomatic patients with bacterascites (bacterial growth from ascitic fluid) with a PMN count <250 cells/uL