HRCT Findings in Pulmonary Veno-Occlusive Disease
The characteristic HRCT triad for PVOD consists of subpleural thickened septal lines, centrilobular ground-glass opacities, and mediastinal lymphadenopathy—this combination is 100% specific for PVOD in patients with pulmonary arterial hypertension, though only 66% sensitive. 1, 2
The Classic HRCT Triad
The three key radiological features that distinguish PVOD from other forms of PAH are:
Centrilobular ground-glass opacities (cGGO): These appear as patchy areas with a centrilobular distribution (poorly defined centrilobular nodular opacities), which is critical—a panlobular distribution is NOT predictive of PVOD 3
Subpleural thickened septal lines (interlobular septal thickening): These reflect chronic interstitial pulmonary edema characteristic of venous obstruction 1, 2, 4
Mediastinal lymphadenopathy: Enlarged mediastinal lymph nodes (short diameter ≥1 cm) 1, 3
When all three findings are present together, specificity reaches 100% for PVOD with 66% sensitivity 3. The association of ground-glass opacities (particularly with centrilobular distribution), septal lines, and adenopathy strongly indicates PVOD and should prompt extreme caution before initiating vasodilator therapy 3.
Additional Supportive Findings
Beyond the classic triad, HRCT may reveal:
- Pleural effusions 3
- Kerley B lines on standard chest radiograph 3
- Diffuse central ground-glass opacification suggesting interstitial edema 3, 4
- Pleural shadows 4
Critical Clinical Context
HRCT is the investigation of choice for suspected PVOD 1. The presence of these findings is clinically crucial because:
They strongly correlate with risk of life-threatening pulmonary edema when PAH-specific vasodilator therapy (especially prostanoids) is initiated 1, 3
They can establish diagnosis with high probability without requiring lung biopsy, which is contraindicated in suspected PVOD due to high complication risk 1
They should trigger immediate referral to a transplant center, as lung transplantation is the only curative therapy 2
Important Caveats
Sensitivity limitations: Recent pathology data shows that some PVOD cases lack the complete triad—in one study, only 71.4% of pure PVOD cases had at least two of three features 5
Context matters: The diagnostic accuracy is highest in pure PVOD; sensitivity drops significantly when PVOD occurs with fibrotic interstitial lung disease (only 16.7% had two of three features) 5
Not all findings are equal: The morphologic feature of ground-glass opacities matters—centrilobular distribution is predictive (p=0.03), while panlobular distribution is not 3
Clinical correlation essential: HRCT findings must be interpreted alongside severe hypoxemia and markedly reduced DLCO (typically much lower than other PAH forms) 1, 2
Bottom line: If you see the triad on HRCT in a patient with precapillary pulmonary hypertension, assume PVOD until proven otherwise, avoid standard PAH vasodilators, and refer urgently for transplant evaluation.