Hepatopulmonary Syndrome



Hepatopulmonary Syndrome


Jud W. Gurney, MD, FACR





Key Facts


Terminology



  • Triad characterized by



    • Chronic liver disease (usually cirrhosis)


    • Increased alveolar-arterial oxygen gradient on room air (> 15 mmHg)


    • Intrapulmonary vascular dilatation


Imaging Findings



  • Best imaging finding: Dilated peripheral arteries on CT



    • Arterial bronchus ratio in periphery usually > 2


  • MIP reconstructions or thick sections better depict vascular abnormality than HRCT


  • Nuclear medicine: Macroaggregated albumin bypasses lungs and results in systemic activity in brain and kidneys


Top Differential Diagnoses



  • Pulmonary Artery Hypertension


  • Pulmonary Arteriovenous Malformation


  • Intravascular Metastases


Pathology



  • No correlation between hypoxemia in HPS and severity of liver disease (Child classification)


Clinical Issues



  • Dyspnea presenting symptom in 20%



    • Platypnea 90%: Dyspnea in upright position, relieved with supine position


  • Reversible after orthotopic liver transplantation (80%) (20% do not improve)







Axial CECT shows enlarged pulmonary arteries image compared to adjacent airways image. Ratio of arterial diameter to bronchus is greater than 2.






Axial CECT MIP reconstruction shows enlarged pulmonary arteries extending to the lung periphery image in a patient with hepatopulmonary syndrome.


TERMINOLOGY


Abbreviations and Synonyms



  • Hepatopulmonary syndrome (HPS), chronic obstructive pulmonary disease (COPD), pulmonary alveolar-arterial gradient = PAO2-PaO2


Definitions



  • Triad characterized by



    • Chronic liver disease (usually cirrhosis)


    • Increased alveolar-arterial oxygen gradient on room air (> 15 mmHg)


    • Intrapulmonary vascular dilatation


IMAGING FINDINGS


General Features



  • Best diagnostic clue: Dilated peripheral arteries (2x larger than adjacent bronchi) on CT


  • Patient position/location: Lower lobes


  • Size: Arterial bronchus ratio in periphery usually > 2


CT Findings



  • Peripheral arteries dilated (artery larger than accompanying bronchus)



    • Normal bronchoarterial relationship



      • 1:1, arterial diameter = bronchial diameter


      • Arteries may be slightly larger in dependent lung (1.2 ± 0.2) due to gravity


    • HPS ratio typically (2.0 ± 0.2)



      • Pulmonary artery diameter inversely correlated with PaO2


    • MIP reconstructions or thick sections better depict vascular abnormality than HRCT


  • Peripheral arteries may extend to pleural surface



    • Normally arteries become invisible 5-10 mm from pleural surface


  • Enlarged main pulmonary artery


  • Cirrhosis



    • Nodular liver contour, small liver, relative hypertrophy of left hepatic lobe


    • Splenomegaly


    • Esophageal or gastric varices


    • Ascites



  • Comorbid conditions, especially centrilobular emphysema or pleural effusions (from ascites or hypoproteinemia) common


Radiographic Findings



  • Radiography



    • May be normal


    • Main pulmonary artery may be enlarged


    • Mild cardiomegaly


    • Small nodular opacities in bases from dilated vessels



      • Seen in 5% with cirrhosis, 50% of those with proven HPS


    • Lung volumes normal (or enlarged if coexisting COPD)


    • Portal hypertension associated findings



      • Splenomegaly


      • Ascites


      • Small right or bilateral pleural effusions


      • Retrocardiac paraspinal widening from varices


Nuclear Medicine Findings

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Sep 20, 2016 | Posted by in RESPIRATORY IMAGING | Comments Off on Hepatopulmonary Syndrome

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