All participants in the study will receive standard of care antibiotic therapy and supportive care for spontaneous bacterial peritonitis. Prior to screening, a paracentesis will have been performed and the resulting ascitic fluid sent to the lab for cell count and bacterial culture. Ascites culture media will be inoculated at the bedside with at least 10ml of fluid per culture container. Once the diagnosis of SBP is established, the patient will receive a complete history and physical examination, chest and abdominal radiographs, ultrasound examination of the liver including Doppler exam of the hepatic veins, arteries, and portal vein to evaluate for thrombosis, peripheral blood laboratory testing including a complete blood count with differential, standard serum chemistry and electrolytes including blood urea nitrogen (BUN) and creatinine, liver panel assay including aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), total, direct, and indirect bilirubin, prothrombin time (PT), partial thromboplastin time (PTT), international normalized ratio (INR), plasma renin activity (PRA), serum aldosterone level, and brain natriuretic peptide (BNP) level. Peripheral blood cultures will be obtained in standard fashion as per institutional protocols with inoculation of blood and body fluid samples directly into culture media at the bedside and similarly, central line blood cultures will be obtained if applicable. Complete blood cell counts, serum chemistry, and hepatic panels will be repeated at least daily for the first three days after diagnosis and at least every other week thereafter until 30 days. Levels of PRA, aldosterone, and BNP will be measured at study entry and on days two and three in the protocol, and again at day 30. Baseline quality of life will be assessed at enrollment and at 30 days. If the subject has consented to tissue banking, samples of blood, ascites, and urine will be collected and prepared for storage by study personnel. Tissue banking samples will be collected at enrollment, 3 days, and at 30 days from each participating subject.