• The study will be a prospective open labelled double blinded randomized controlled study.
• The study will be conducted on patients admitted to Department of Hepatology from 2012 to 2014 at Institute of Liver and Biliary Sciences, New Delhi
• Patients diagnosed as having clinical or subclinical hepatopulmonary syndrome will be started on oral pentoxifylline therapy 400 mg thrice daily for 12 weeks.
• Patients not responding to this therapy will be given divided into 2 arms with one arm receiving additional Tab Rifaximin 400 mg thrice daily or placebo for 12 weeks.

Inclusion Criteria:

1. Evidence of portal hypertension (esophagogastric varices or portal hypertensive gastropathy identified on esophagogastroduodenoscopy, and/or varices seen on computerized tomography scan or ultrasound, and/or splenomegaly with no other explanation, and/or ascites with no other explanation)
2. Intrapulmonary vascular dilatations (IPVDs) diagnosed on contrast echocardiogram (CE)
3. AaDO2 > 15 mm Hg on standing room air arterial blood gas (ABG)
4. Ability and willingness to give informed consent

Exclusion Criteria:

• Age < 18 or > 64
• Intrinsic significant cardiopulmonary disease
• Inability to perform pulmonary function tests
• Moderate to severe Pulmonary hypertension
• Advanced hepatic encephalopathy
• Inadequate echocardiographic window to allow for accurate transthoracic contrast echocardiography
• Antibiotic use within the last one month
• Listed for liver transplant in next 4 weeks
• Current use of exogenous nitrates
• Active bacterial infections
• Known malignancy
• Known intolerance to Pentoxifylline or rifaximin