Discussion
Diagnosis With Brief Discussion
- Diagnosis
- Hepatopulmonary Syndrome
- Radiologic Findings
- Chest radiograph shows diffuse reticulonodular opacities throughout the lungs. CT scan (lung window settings) obtained at the level of lung bases shows dilated peripheral pulmonary vessels and an abnormally large number of visible terminal vessel branches.
The presence of right-to-left shunt was confirmed by contrast echocardiography.
- Brief Review
- Hepatopulmonary syndrome is characterized by the triad of chronic liver disease, increased alveolar-arterial oxygen gradient on room air (hypoxemia), and evidence of intrapulmonary vascular dilation. The most consistent structural abnormality found in HPS is marked dilation (up to 500 mm) of precapillary vessels in the lung and pleura. The mechanism for this dilation is unknown. When small vessels are dilated, the diffusion of oxygen to the centers of the vessels is insufficient, and erythrocytes flowing down the center do not get fully oxygenated, resulting in a right to left shunt. The deficiency of oxygenation is further exacerbated by the hyperdynamic circulation, which decreases transit time. The presence of intrapulmonary right-to-left shunt can be demonstrated by contrast echocardiography or 99mTc macroaggregated albumin (MAA) lung scanning. The rationale for both diagnostic modalities in HPS is that the microbubbles (at least 15 mm) used for contrast echocardiography or the aggregated albumin (20-60 mm) for 99mTcMAA lung scanning can pass through dilated, but not normal, pulmonary capillaries (less than 8 mm in diameter).
On chest radiographs, intrapulmonary vascular dilation of HPS may manifest as small nodular or reticulonodular opacities, predominantly in the bases. The frequency of these findings is 46% to 100% of cases. The CT feature of HPS is dilation of peripheral lung vessels with many extending to the pleura. Thick scans depict this vascular abnormality better than thin-section (high-resolution) scans. There are two patterns of vascular abnormality on pulmonary angiography in HPS. Type I lesions (86%) manifest as a diffuse spongy appearance during the arterial phase; type II lesions (14%) manifest as discrete arteriovenous malformations.
- References
- 1. Lee KN, Lee HA, Shin WW, Webb WR. Hypoxia and liver cirrhosis (hepatopulmonary syndrome) in eight patients: comparison of the central and peripheral pulmonary vasculature. Radiology 1999;211:549-53.
2. Oh YW, Kang EY, Lee NJ, Suh WH, Godwin JD. Thoracic manifestations associated with advanced liver disease. J Comput Assist Tomogr 2000;24:699-705
- Keywords
- Vascular, Lung, Vascular,