Diagnostic Approach to Right Hilum Enhancement on Chest X-Ray

Primary Vascular Causes

Enlargement of the right descending pulmonary artery >15 mm in women (>16 mm in men) at the hilum is highly suggestive of pulmonary hypertension, with sensitivity of 93%, specificity of 88%, and accuracy of 92% 1, 2
The main pulmonary artery enlargement (>35 mm from midline to left lateral border) occurs in 96% of pulmonary hypertension cases 1, 2
Additional findings include central pulmonary artery enlargement with rapid tapering (pruning) and right heart chamber enlargement 1, 2, 3
Chest radiography has high sensitivity (96.9%) and specificity (99.1%) for detecting moderate to severe pulmonary hypertension 1, 2

Chest X-ray is the appropriate first-line imaging study, though it has limitations in determining the underlying cause 1, 2, 4
Measure the right descending pulmonary artery diameter at the hilum on posterior-anterior view to assess for pulmonary hypertension 1, 2
Evaluate for associated findings: cardiac enlargement, pulmonary vascular pruning, or parenchymal abnormalities 1, 2, 3

CT scan of the chest with contrast is the gold standard for definitive diagnosis when chest X-ray findings are abnormal or inconclusive 4, 5
MRI can provide additional information when CT findings remain inconclusive, particularly for vascular assessment 6

Transthoracic Doppler echocardiography should be performed when pulmonary hypertension is suspected, with sensitivity of 85% and specificity of 74% for moderate to severe disease 1, 2

Normal chest radiographs do not exclude significant pathology; if clinical suspicion persists with unexplained symptoms, proceed directly to CT imaging 1, 2, 4, 5
Chest X-ray is insensitive for mild pulmonary hypertension; further evaluation with echocardiography is warranted when symptoms suggest elevated pulmonary pressures despite normal-appearing hilar vessels 1, 2