Pulmonary complications of portal hypertension

Pulmonary complications of portal hypertension include hepatopulmonary syndrome (HPS), portopulmonary hypertension (POPH), and hepatic hydrothorax. HPS is caused by intrapulmonary vascular dilatations leading to impaired oxygenation and dyspnea; the presence of liver disease and/or portal hypertension, abnormal gas exchange, and evidence of shunting on contrast-enhanced transthoracic echocardiogram (TTE) confirms the diagnosis. POPH is a type of pulmonary arterial hypertension characterized by precapillary pulmonary hypertension in patients with portal hypertension in the absence of an alternative cause; manifestations include exertional dyspnea and signs of right heart failure. Diagnosis involves TTE screening and is confirmed by elevated mean pulmonary artery pressure (mPAP), elevated pulmonary vascular resistance (PVR), and normal pulmonary capillary wedge pressure (PCWP) on right heart catheterization (RHC). Hepatic hydrothorax is typically a right-sided transudative pleural effusion that develops in the absence of underlying cardiopulmonary, malignant, or kidney disease; it is thought to arise from the passage of ascitic fluid through small diaphragmatic defects. Complications of hepatic hydrothorax include spontaneous bacterial empyema (SBEM), which is an infection of an existing pleural effusion in the absence of pneumonia; it is diagnosed on pleural fluid analysis. Management of these conditions includes long-term oxygen therapy (LTOT) in HPS and POPH; targeted treatment of pulmonary hypertension in POPH; sodium restriction and, in some cases, transjugular intrahepatic portosystemic shunt (TIPS) in hepatic hydrothorax; and antibiotics in SBEM. Liver transplantation is the only definitive treatment for most pulmonary complications of portal hypertension.

Portal hypertension-related pulmonary complications

Other pulmonary complications of cirrhosis ^[4]

• Pneumonia: caused by cirrhosis-associated immune dysfunction and aspiration in hepatic encephalopathy
• Atelectasis: secondary to diaphragmatic elevation from massive ascites
• Chronic obstructive pulmonary disease: in patients with alpha-1 antitrypsin deficiency-related cirrhosis

Definition ^[1]

HPS is a pulmonary vascular complication of liver disease and/or portal hypertension characterized by intrapulmonary vascular dilatations that result in impaired gas exchange and hypoxemia.

Epidemiology ^[5]

• Prevalence varies based on disease severity and the diagnostic criteria used.
• Patients with cirrhosis: prevalence up to 30%

Pathophysiology

• Not completely understood
• Portal hypertension and liver damage → translocation of bacterial endotoxins → changes in the production of cytokines and pulmonary vasodilators → ↑ nitric oxide in the lung vessels → pulmonary vasodilation → HPS

Classification ^[1]

HPS severity is classified based on PaO₂ level.

• Mild: PaO₂ ≥ 80 mm Hg
• Moderate: PaO₂ 60–79 mm Hg
• Severe: PaO₂ 50–59 mm Hg
• Very severe: PaO₂ < 50 mm Hg

Clinical features ^[1][6]

• Often asymptomatic
• Clinical features of chronic hypoxia, e.g.:
  • Dyspnea (at rest or exertional dyspnea)
  • Platypnea
  • Orthodeoxia
  • Nail clubbing
  • Cyanosis
• Clinical features of cirrhosis (e.g., spider angiomata)

Diagnosis ^[1][6][7]

• Pulse oximetry: (screening study): hypoxemia ^[7]
• Arterial blood gas
  • Obtained while the patient is seated and breathing ambient air
  • Findings
    • ↑ Alveolar-arterial gradient ≥ 15 mm Hg (> 20 mm Hg if > 64 years of age) ^[1][7]
    • ↓ PaO₂ in moderate to severe disease
• Imaging ^[1]
  • Contrast-enhanced TTE (criterion standard): microbubbles observed in the left heart ≥ 3 cardiac cycles after the right heart
  • Lung perfusion scintigraphy (Tc-99m macroaggregated albumin): alternative study to identify intracardiac and intrapulmonary shunts
• Diagnostic criteria: All criteria must be fulfilled. ^[7]
  • Presence of liver disease and/or portal hypertension: See "Diagnosis of portal hypertension."
  • Abnormal arterial oxygenation: confirmed by ↑ alveolar-arterial gradient
  • Intrapulmonary vascular dilatations ; and/or shunting: confirmed on imaging (e.g., contrast-enhanced TTE)

Management ^[1][6][7][8]

There are no effective pharmacological treatments for HPS.

• LTOT ^[6]
  • Measure pulse oximetry every 6–12 months to assess the need for LTOT.
  • Indications for home oxygen therapy: PaO₂ ≤ 55 mm Hg, SaO₂ ≤ 88%
• Liver transplant: definitive treatment ^[1][8]
  • Transplant evaluation is indicated in patients with severe disease (PaO₂ < 60 mm Hg). ^[1][8]
  • Complication: severe post-transplant hypoxemia ^[1]
    • Due to ventilation-perfusion mismatch from disproportionate vasoconstriction in nonimpaired pulmonary vasculature
    • Initial management requires restoration of ventilation-perfusion equilibrium (e.g., Trendelenburg position, inhaled vasodilators).
    • Mortality: 45%
  • In most patients, HPS resolves within 6–12 months post-transplant.^[1]

Severe post-transplant hypoxemia is a common complication after liver transplant for HPS and has a mortality rate of up to 45%. ^[1]

Prognosis ^[1]

The 5-year survival rate depends on the management strategy.

• Without liver transplant: ∼ 23%
• With liver transplant: ∼ 76%

Definition ^[9]

POPH is a type of pulmonary arterial hypertension characterized by precapillary pulmonary hypertension in patients with portal hypertension in the absence of an alternative cause; manifestations include exertional dyspnea and signs of right heart failure.

Epidemiology ^[2]

The prevalence in patients with portal hypertension is 2–10%.

Risk factors ^[2]

• Female sex
• Autoimmune hepatitis

Pathophysiology

• Not completely understood
• High cardiac output in advanced liver disease → wall shear stress in pulmonary vasculature → ↑ vasoactive and angiogenic substances (e.g., endothelin-1) → hypertrophy of smooth muscle cells and fibroblasts, fibrosis of intimal sheath, and microaneurysms of pulmonary arterioles

Classification ^[9]

Hemodynamic severity of POPH is based on mPAP.

• Mild: mPAP 21–34 mm Hg
• Moderate: mPAP 35–44 mm Hg
• Severe: mPAP ≥ 45 mm Hg

Clinical features ^[2]

• Often asymptomatic in early stages
• Typical symptoms include:
  • Exertional dyspnea
  • Fatigue
  • Chest pain
  • Presyncope and/or syncope
  • Peripheral edema
• Features of pulmonary hypertension
• Clinical features of right heart failure are often present.

Diagnosis ^[9]

• TTE: findings suggestive of pulmonary hypertension
  • Elevated tricuspid regurgitant velocity (RVSP > 40 mm Hg) ^[9]
  • Signs of RV pressure overload (e.g., RV hypertrophy and/or dilation)
• RHC: findings suggestive of precapillary pulmonary hypertension
  • ↑ mPAP
  • ↑ PVR
  • Normal PCWP
• Diagnostic criteria: All criteria must be fulfilled. ^[9]
  • Clinical features of portal hypertension and/or hepatic venous pressure gradient > 5 mm Hg
  • mPAP > 20 mm Hg
  • PVR > 2 Wood units
  • PCWP ≤ 15 mm Hg

Other causes of pulmonary hypertension must be excluded to confirm the diagnosis of POPH.

Management ^[2][9]

Management is guided by a multidisciplinary team. See also: "Treatment of pulmonary hypertension."

• Supportive care
  • Diuretics for volume overload
  • LTOT if SaO₂ ≤ 88% ^[2]
• Pharmacological therapy
  • Pulmonary vasodilators (e.g., endothelin receptor antagonists, PDE5 inhibitors) may be effective.
  • Avoid beta blockers.
  • Anticoagulation is not routinely recommended.
• Liver transplant: definitive treatment
  • Potentially curable but high perioperative risk (e.g., RV failure)
  • Absolute contraindications include: ^[9]
    • mPAP greater than 45–50 mm Hg
    • PVR > 5 Wood units
    • Severe RV dysfunction

Avoid TIPS in patients with POPH. ^[9]

Prognosis ^[2]

The 5-year survival rate depends on the management strategy.

• Untreated POPH: 14%
• Treatment of pulmonary hypertension without liver transplant: 45%
• Treatment of pulmonary hypertension with liver transplant: 67%

Definition ^[3]

Hepatic hydrothorax is a typically right-sided transudative pleural effusion that develops in patients with liver disease and portal hypertension in the absence of underlying cardiopulmonary, malignant, or kidney disease.

Epidemiology ^[3]

• Prevalence
  • 5–16% of individuals with cirrhosis
  • ∼ 90% of individuals with decompensated cirrhosis
• Location: typically right-sided (∼ 85%)

Pathophysiology ^[3]

• Thought to develop due to the direct passage of ascitic fluid into the pleural space through small diaphragmatic defects
• Contributory factors: ↑ intra-abdominal pressure and negative intrathoracic pressure

Clinical features ^[3]

• May be asymptomatic
• Clinical features of pleural effusion (e.g., dyspnea)
• Clinical features of cirrhosis (e.g., ascites)

Hepatic hydrothorax occurs without ascites in ∼ 10% of cases. ^[3]

Diagnosis ^[3]

Suspect hepatic hydrothorax in any individual with underlying liver disease who presents with a pleural effusion, particularly if it is right-sided.

• Imaging
  • Chest x-ray: confirms pleural effusion
  • Abdominal ultrasound: to evaluate for ascites and features of cirrhosis and portal hypertension
• Diagnostic thoracentesis: confirmatory once alternative causes (e.g., heart failure) have been excluded
  • Primary pleural fluid analysis: transudative pleural effusion
  • Pleural fluid cell count and differential: neutrophil count < 250 cells/mm³
  • Pleural fluid culture: negative

Exclude other causes of transudative pleural effusions (e.g., heart failure, nephrotic syndrome).

Management ^[3][10][11]

• Medical management: similar to the treatment of ascites
  • Dietary sodium restriction (< 2 g/day) ^[10]
  • Diuretics (e.g., spironolactone ± furosemide)
• Symptomatic management
  • Therapeutic thoracentesis
    • Repeat sessions may be required.
    • Routine periprocedural albumin infusion is not recommended. ^[3]
  • Large volume paracentesis in patients with ascites
• Surgical management: video-assisted thoracoscopic surgery (VATS) ± repair of diaphragmatic defects
• Definitive therapy: Consider for refractory or recurrent hepatic hydrothorax.
  • TIPS
  • Liver transplant

Consider liver transplant evaluation for all patients with refractory ascites and/or hepatic hydrothorax. ^[10]

Complications ^[3]

• Respiratory failure
• SBEM
• Complications of thoracentesis

Definition ^[6]

SBEM is an infection of an existing pleural effusion in the absence of pneumonia; it most often occurs as a complication of hepatic hydrothorax.

Etiology ^[3][6]

• Risk factors
  • Advanced liver disease (e.g., ↑ Child-Pugh score)
  • ↓ Total protein and albumin levels in pleural fluid and/or serum
  • ↓ C3 complement levels in pleural fluid
• Microbiology
  • Organisms similar to those causing spontaneous bacterial peritonitis, e.g.:
    • Escherichia coli
    • Klebsiella spp.
    • Streptococcus spp.
    • Enterococcus spp.
  • Multidrug-resistant organisms may be present, especially in patients with frequent hospitalizations.

Clinical features ^[3][6]

Clinical features are typically nonspecific and may include:

• Pleuritic chest pain
• Fever
• Signs of decompensated cirrhosis (e.g., hepatic encephalopathy)

Diagnosis ^[3][6]

• Diagnostic thoracentesis
  • Primary pleural fluid analysis: may be transudative or exudative
  • Diagnosis is confirmed if pleural fluid analysis shows one of the following: ^[3]
    • Neutrophil count > 250/mm³ and a positive bacterial culture
    • Neutrophil count > 500/mm³ and a negative bacterial culture ^[6]
• Imaging (e.g., contrast-enhanced CT chest): may help identify loculated collections

Differential diagnoses ^[12]

• Uncomplicated hepatic hydrothorax
• Parapneumonic effusion
• Empyema from other causes

Treatment ^[6][8][11]

Treatment of SBEM is similar to the treatment of spontaneous bacterial peritonitis.

• Antibiotics
  • Initiate empiric antibiotic therapy immediately after pleural fluid sampling.
    • Community-acquired infection: third-generation cephalosporin (e.g., cefotaxime)
    • Health care-associated infection: broad-spectrum antibiotics based on local resistance patterns
  • See Empiric antibiotic therapy for spontaneous bacterial peritonitis" for agents and dosages.
• Consider IV albumin substitution.
• Therapeutic thoracentesis and/or VATS: indicated for symptomatic effusions, purulent fluid, or loculated effusions

Repeat thoracentesis after 2 days to assess the response to empiric antibiotics; broaden antibiotic coverage if pleural fluid neutrophil count decreases < 25% from baseline measurement. ^[11]

Prognosis ^[3]

SBEM has a mortality rate of 20–38% despite treatment.