Hepatopulmonary Syndrome

Epidemiology

  • Incidence
    • Positive echo bubble study (due to intrapulmonary shunt) is seen in 20% of cirrhotics (although not all are hypoxemic)
    • Hepatopulmonary syndrome occurs in 5-30% of patients with liver disease

Physiology

  • Hepatogenic Pulmonary Angiodysplasia: results in intrapulmonary (right-to-left) shunting
    • Intrapulmonary vascular dilatations (more prominent in the bases)
    • Dysfunctional pulmonary vasoconstriction

Diagnostic

  • Echo with Bubble Study
    • Preferred study
    • Bubbles in left heart immediately after injection: suggests intracardiac shunt
    • Bubbles after 3-6 cardiac cycles after injection: suggests intrapulmonary shunt
  • V/Q Shunt Study
    • Procedure: scan over brain and kidneys to assess amount of Te99m-MAA that has traversed the pulmonary circulation -> presence in these organs indicates intrapulmonary shunt
    • 20-60 ┬Ám Te99m-MAA (macro-aggregated albumin) particles are normally trapped in pulmonary circulation
    • Quantification (by kidney:dose method): shunt = (right kidney counts x 10)/injected dose
    • Quantification (by kidney:lung method): shunt = (right kidney counts x 10)/[total lung counts + (right kidney counts x10)]
  • Swan
    • High CO with normal-low PVR
  • ABG
    • Increased A-a gradient
  • PFT’s
    • Decreased DLCO
  • 100% FIO2 Shunt Study
    • pO2 <500-600 -> suggests presence of intrapulmonary shunt
  • Chest CT
    • May demonstrate subpleural vessels
  • Pulmonary Angiogram
    • May demonstrate spidery-spongy vascular dilatations
  • ABG: hypoxemia/ respiratory alkalosis
    • Shunt physiology: hypoxemia may respond somewhat to supplemental O2 (due to a “diffusion perfusion defect”: vascular dilatations prevent oxygen from diffusing to the center of vessel to provide adequate oxygenation)
    • Orthodeoxia (due to increased flow to bases, where vascular dilatations are more prominent, with standing): supine position improves hypoxemia
  • CXR/ Chest CT Patterns
    • Bibasilar interstitial changes: most cases
    • Normal CXR: some cases

Clinical Manifestations

Pulmonary Manifestations

  • Exertional Dyspnea (see Dyspnea, [[Dyspnea]]): dyspnea is the first symptom in only 20% of cases (usually liver symptoms precede onset of dyspnea)
  • Hypoxemia (see Hypoxemia, [[Hypoxemia]])
  • Orthodeoxia (see Platypnea-Orthodeoxia, [[Platypnea-Orthodeoxia]]): characteristic worsened hypoxemia with upright position
  • Platypnea (see Platypnea-Orthodeoxia, [[Platypnea-Orthodeoxia]]): dyspnea with upright position (as vascular diltations are basilar-predominant)

Rheumatologic Manifestations

Other Manifestations

  • Spider Angiomata
  • Hypotension (see Hypotension, [[Hypotension]])
  • Acrocyanosis (see xxxx, [[]])

Prognosis

  • Median Survival: 41 mo after diagnosis of hepatopulmonary syndrome
  • Hepatopulmonary syndrome is a poor prognostic factor

Treatment

  • Supplemental O2: for patients with small shunts
  • Orthotopic Liver Transplant
    • Preferred treatment: effective in most cases
    • Higher operative mortality with shunt fraction >20% or pre-op pO2 <50
  • Indomethacin: may be useful but unproven
  • Coil Spring Embolization of Vascular Dilatations: may be used but not always effective (due to multiple areas)
  • Octreotide: no benefit shown in 2 studies

References

  • xxx