Natural history

• Present in ~ 25% of chronic liver disease, increased risk with portal hypertension
• Due to limited venous flow to the lung
• Portal hypertension -> bacterial translocation/toxin release -> NO, TNFa -> pulmonary vasodilation/angiogenesis
• Liver fails to clear these circulating pulmonary vasodilators/produces more (ET-1 -> increased production of NO)/inhibition of faosconstrictors
• Pulmonary vasodilation/arteriovenous connections from angiogenesis -> V/Q mismatch - increased blood flow with restricted diffusion -> hypoxemia (mixed venous blood passing into pulmonary veins due to increased blood flow, restricted diffusion because intrapulmonary vascular dilation causes increased diameter)

• Dyspnea, platypnea/orthodeoxia (dyspnea/O2 sat worse when standing up) - IPVD preferential in lung bases so V/Q mismatch worse when standing up
• Other causes of dyspnea - hepatic hydrothorax, ascites, fluid retention, etc.
• Hypoxemia
• Can have increased bibasilar interstitial markings
• Decreased diffusing capacity DLCO (nonspecific)
• Correlates with spider nevi

• Suspect in chronic liver disease + dyspnea, hypoxemia (e.g. O2 sat < 96%), platypnea, spider nevi
• ABG on room air while sitting upright - A-a >= 15 or PaO2 < 80 -> contrast echo bubble study to see if intrapulmonary shunt presesnt (bubbles will pass from R to L heart because not everything filtered in lungs) (will show up 3-8 beats later isntead of 1 beat later with intracardiac shunt)
• Mild - PaO2 > 80, moderate 60-80, severe 50-60, very severe < 60
• severe/very severe -> O2, liver transplant

• Mild/moderate - supportive care, q6-12 mo montioring with O2 sats/ABG, oxygen supplementation if needed
• Only definitive treatment is liver transplantation
• In initial 6-12 months, observational studies show near/complete resolution with improved oxygenation and shunt in ~ 80% patients
• Counts as a MELD exception (HCC, HPS, CF, hepatic artery thrombosis, etc...)
• Stanard exception of 22
• Mortality 78% vs 21%; similary 5-year survival after transplant compared to non-HPS with transplant
• Unclear if severity of HPS correlates w survival after transplant