Hepatopulmonary Syndrome (HPS)

1. Liver disease (liver dysfunction or portal hypertension)
2. Intrapulmonary vascular dilatations or IPVDs (widening of blood vessels entering the lungs)
3. Hypoxia/ abnormal oxygenation.
   

Clinical Manifestations

• Patients typicaly present with liver disease, 18% can present with primary lung complaints
• Shortness of breath at rest or with exertion, Hypoxia with activity is characteristic of HpS
• Hypoxemia prgresses over time
• Specific finding = Platypnea: breathlessness in the upright position that is improved with lying down
• Specific finding = Orthodeoxia: drop of 4mmHg in PaO2 or 5% in Sats when moving from the supine to standing position
• Correlates to Platypnea
• Seen in 88% of HPS patients
• Spider angiomata
• Clubbing of the fingers
• Cyanosis

Diagnosis

• O2 Sat <96% and Platypnea, orthodeoxia, clubbing, or cyanosis should be evaluated for HPS
• PaO2 < 80 mmHg or A-a gradient >15 that is not explained by alternative Dx, should be evaluated for HSP
  
• Diagnosis made after confirming the Triad noted above
• Confirmation of Liver disease, Cirrhosis, or portal hypertension (Ultrasound, LFTs, Bx)
  
• PFTs, 6min walk test w or w/o oxygen titration, Contrast-enhanced echocardiography (CEE or bubble echo) can detect intrapulmonary vascular dilation
• Hypoxemia: Oxygen partial pressure <70 mm Hg or an increase in alveolar-arterial oxygen gradient >15 mm Hg (> 20 if patient is over age 64
• CXR and Thoracic CT are often unremarkable
  

Treatment

• Significant improvement in oxygenation is seen in the majority of patients within one year of transplantation
• Long term O2 therapy for supportive care pre & post op
  

Hepatopulmonary Syndrome in Pediatrics

Definition and core pathophysiology

Hepatopulmonary syndrome (HPS) is the triad of:

• Chronic liver disease or portal hypertension, 
• Intrapulmonary vascular dilatations (IPVDs) or arteriovenous shunts,
  
• Arterial hypoxemia

Mechanisms and contributing factors

• Nitric oxide and other vasodilators: Overproduction of nitric oxide in the pulmonary circulation is a major mediator of vasodilation and IPVD formation.
• Angiogenesis and vascular remodeling: Increased pulmonary angiogenic signaling produces abnormal microvascular networks and direct arteriovenous connections.
• Gut–liver–lung axis and inflammation: Portal hypertension and portosystemic shunting permit gut-derived bacterial products and inflammatory mediators to bypass hepatic clearance and trigger pulmonary endothelial activation.
• Resulting gas-exchange abnormalities: IPVDs increase perfusion of poorly ventilated lung regions, enlarge capillaries to exceed diffusion limits for oxygen, and create true shunts that are refractory to increased FiO2.

Clinical features in pediatrics

Symptoms

• Dyspnea, often progressive.
• Exertional intolerance and fatigue.
• Platypnea, shortness of breath when upright that improves when supine.
• Orthodeoxia, a clinically meaningful drop in PaO2 or SpO2 when moving from supine to upright.

Signs

• Cyanosis.
• Digital clubbing.
• Spider angiomas or telangiectasias.
• Exercise desaturation on exertion testing.
• Many children may be minimally symptomatic or asymptomatic, contributing to under-recognition.

Epidemiology and risk settings

• Most commonly associated with cirrhosis and portal hypertension.
• Also occurs with chronic inflammatory liver disease and vascular anomalies such as Budd–Chiari syndrome and congenital portosystemic shunts (Abernathy malformation).
• Reported incidence varies by population and screening intensity because many patients are asymptomatic.

Diagnostic approach and tests

Clinical definition and thresholds

HPS diagnosis requires documented liver disease or portal hypertension, intrapulmonary vascular dilatations or shunting, and arterial hypoxemia. Commonly applied laboratory thresholds include a reduced resting PaO2 or an increased alveolar–arterial oxygen gradient adjusted for age.

First-line screening

• Transthoracic contrast echocardiography with saline microbubble study demonstrating microbubbles in the left heart after three or more cardiac cycles, consistent with intrapulmonary shunting.

Confirmatory and adjunct tests

• Arterial blood gas for PaO2 and A–a gradient and for documenting orthodeoxia by comparing supine and upright values.
• 99mTc-labeled macroaggregated albumin (MAA) scan to quantify right-to-left shunt fraction.
• Contrast-enhanced transthoracic or transesophageal echocardiography to exclude intracardiac shunt when timing suggests intracardiac passage.
• Chest computed tomography to show increased vascular markings in lower lobes or vascular changes and to exclude other pulmonary pathology; CT is not diagnostic alone but may help locate macroscopic AV malformations.
• Pulmonary angiography reserved for severe hypoxemia to identify large arteriovenous malformations amenable to embolization.

Severity classification

Use PaO2 or A–a gradient to stage severity for clinical decision-making and transplant listing.

Management and prognosis (pediatrics emphasis)

Definitive therapy

Liver transplantation is the only proven curative therapy; oxygenation commonly improves over months after transplant, often within six to twelve months, though some patients require longer-term supplemental oxygen.

Supportive measures until transplant

• Supplemental oxygen titrated to maintain acceptable saturation and relieve symptoms.
• Activity modification and monitoring for progressive hypoxemia and growth or functional decline.
• Embolization of large, discrete pulmonary arteriovenous malformations identified on angiography when feasible as a bridge or temporizing measure.

Medical therapies

No consistently effective pharmacotherapy is established. Agents tried in adults and reported in small pediatric series include somatostatin analogs, methylene blue, pentoxifylline, and gut-directed antibiotics; these are investigational and not standard of care in children.

Transplant candidacy and outcomes

• HPS increases pretransplant morbidity and mortality; severity of hypoxemia correlates with outcomes.
• Many transplant programs consider MELD/PELD exception points or additional priority for severe HPS; listing criteria vary by center and region.
• Post-transplant oxygenation usually improves, but close cardiopulmonary follow-up is required and some patients may have persistent need for oxygen for months to years.

Perioperative, screening, and practical considerations for pediatric learners

Screening strategy

Maintain a low threshold for screening children with advanced liver disease or portal hypertension for HPS using pulse oximetry and contrast echocardiography, especially with unexplained dyspnea, digital clubbing, or platypnea/orthodeoxia.

Orthodeoxia testing

Measure PaO2 or SpO2 supine then upright; a clinically meaningful drop supports HPS diagnosis.

Pre-transplant optimization

• Optimize oxygenation and treat infections.
• Assess for large focal shunts and consider embolization if feasible.
• Coordinate cardiopulmonary and transplant teams early in the evaluation and listing process.

Anesthesia and perioperative risk

Children with HPS are at elevated risk for perioperative hypoxemia. Plan for higher FiO2 needs, invasive monitoring, and careful fluid management to avoid worsening ventilation–perfusion mismatch.

Differential diagnoses to exclude

• Intracardiac shunt such as patent foramen ovale or atrial septal defect.
• Primary pulmonary disease and pulmonary embolism.
• Portopulmonary hypertension, which can coexist and requires separate evaluation.

Distinguishing from portopulmonary hypertension

Portopulmonary hypertension results from pulmonary vasoconstriction, increased pulmonary vascular resistance, and right heart strain. HPS results from pulmonary vasodilation and shunting. Both conditions can coexist and require echocardiography and right-heart catheterization when suspected.

Related pulmonary complication: portopulmonary hypertension

Portopulmonary hypertension is a separate pulmonary complication of end-stage liver disease caused by pulmonary vasoconstriction and vascular remodeling that lead to increased pulmonary vascular resistance and eventual right-sided heart failure. Clinical presentation includes fatigue and dyspnea. Other signs include chest pain, neck vein distension, peripheral edema, and hemoptysis. Diagnosis requires echocardiography and confirmation with right-heart catheterization. Management includes pulmonary vasodilator therapies appropriate for pulmonary arterial hypertension and careful transplant evaluation.

Cardiac and electrophysiologic testing mentioned

• Cardiac angiography is used to diagnose narrowed or blocked coronary vessels when coronary disease is suspected; it is not diagnostic for HPS but may be relevant in pre-transplant cardiovascular evaluation.
• Electrocardiography detects arrhythmias and screens for structural abnormalities such as ventricular hypertrophy and conduction disease that may affect perioperative risk.
• Transesophageal echocardiography provides higher-resolution cardiac anatomy imaging and may be used to exclude intracardiac shunts when transthoracic imaging is inconclusive.

Concise summary and key takeaways

• HPS definition: Presence of intrapulmonary vascular dilatations and shunts that impair oxygen exchange and cause hypoxemia in the setting of liver disease, usually with cirrhosis but also with chronic inflammation and vascular abnormalities.
• Diagnosis: Transthoracic contrast echocardiography demonstrating microbubbles in the left heart after three or more cardiac cycles plus documented hypoxemia in a patient with liver disease.
• Treatment: Liver transplantation is the only proven curative therapy; typical improvement in hypoxia occurs within six to twelve months after transplant, though some patients need oxygen longer.
• Bridging and supportive care: Supplemental oxygen, consideration of embolization for large focal shunts, and close coordination of transplant and cardiopulmonary teams.
• Pediatric emphasis: Low threshold for screening symptomatic or high-risk children because presentation can be subtle and early identification affects transplant timing and outcomes.