Snapshot A 46-year-old man with chronic alcohol abuse and advanced cirrhosis presents with worsening abdominal pain and confusion. On evaluation in the emergency room, his temperature is 101.4°F (38.6°C), blood pressure is 125/80 mmHg, pulse is 106/min, and respirations are 22/min. On physical exam, there is abdominal distension with a fluid wave and diffuse abdominal tenderness to palpation with rebound tenderness. Introduction Clinical definition acute bacterial infection of the peritoneum without obvious focal source Associated conditions alcohol cirrhosis heart failure Budd-Chiari nephrosis systemic lupus erythematosus Epidemiology Occurs in up to 20% of patients with ascites High recurrence rate Most commonly from a single organism Escherichia coli Klebsiella pneumoniae Streptococcus pneumoniae ETIOLOGY Pathogenesis controversial mechanism of inoculation bacterial translocation from the gut hematogenous transmission immune compromise Presentation Symptoms confusion abdominal pain fever vomiting diarrhea Physical exam febrile abdominal tenderness and rebound tenderness distended abdomen with fluid wave flank dullness Studies Diagnostic testing peritoneal fluid analysis diagnostic paracentesis or via peritoneal catheter ultrasound guided if needed white blood cell count ≥ 500 cells/uL neutrophil count ≥ 250 cells/µL Gram stain and culture can be positive or negative pH lactate serum ascites albumin gradient (SAAG) > 1.1 ancillary blood culture urine culture complete blood count chemistries Differential Secondary peritonitis distinguishing factor due to a focal intraabdominal process perforated viscus abscess Nephrolithiasis distinguishing factor nephroliths on imaging Treatment Management approach discontinue nonselective β-blockers start with empiric antibiotics after paracentesis narrow according to cultures, if available albumin infusion First-line antibiotic 3rd generation cephalosporin cefotaxime or ceftriaxone cefotaxime preferred in patients with liver failure as it is renally excreted whereas ceftriaxone is hepatically cleared Complications Renal failure Sepsis and septic shock Death