Patient demographics, clinical details (including Westhaven hepatic encephalopathy grade) and blood haematology, biochemistry (including venous ammonia), microbiology data and neutrophil function will be assessed and collated at baseline and following 30 and 90 days of Rifaximin therapy or placebo. Intestinal permeability will be assessed using the intestinal disaccharide test. Faecal microbiota analysis will be performed by deep pyrosequencing techniques and plasma endotoxemia will be measured (lipopolysaccharide levels) with bacterial DNA quantification as a marker of bacterial translocation. These will all be measured at 3 time points: baseline and at 30 and 90 days after initiation of Rifaximin therapy or matching placebo.