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Weekly Chest CasesImaging Conference Cases

Case No : 5

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  • Age/Sex 31 / M
  • Case Title dyspnea for one week. PHx: Liver cirrhosis for 3 years
  • Figure 1
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Diagnosis With Brief Discussion

Courtesy
K
Imaging Findings
Chest radiograph shows mild dilatation of peripheral pulmonary vasculature in the both lower lungs.

Tc-99m MAA perfusion scan reveals tracer uptake in the brain, thyroid, parotid gland, both kidneys and stomach as well as both lungs.

Echocardiogram demonstrates no significant abnormality.
Discussion
Hepatopulmonary syndrome represents a combination of hypoxemia, hepatic dysfunction, and intrapulmonary vascular dilatation.

This is one of the main causes of arterial hypoxemia in patients with chronic liver disease.

Although the pathogenesis of vascular dilatation is unknown, some investigators have suggested that failure of the damaged liver to clear circulating vasodilators and inhibition of a circulating vasoconstrictive substance by the damaged liver.

Arterial hypoxemia in patients with hepatopulmonary syndrome is thought to occur because of ventilation-perfusion mismatch, limitations in oxygen diffusion due to vascular dilatation, and in some patients, intrapulmonary shunt through dilated vascular malformations.


The radiologic manifestations of this disease include distal vascular dilatation associated with an abnormally large number of visible terminal vessel branches, which are always concentrated in the lower lung zones.

Lee et al. reported that the peripheral pulmonary vessels in the patients with hypoxemic liver cirrhosis were significantly dilated compared with these vessels in the healthy subjects and patients with cirrhosis who were not hypoxemic.

Tc-99m MAA lung scan is a useful method to detect intrapulmonary vascular dilatation. Because the average capillary diameter is approximately 7 μm, the MAA particles, 90 % of which measure 10 to 90 μm, lodge in the first capillary bed they encounter.

A scan showing uptake of radionuclide over the kidneys, brain, or both suggests shunting through the lung caused by an intrapulmonary shunt.

The perfusion lung scan is a simple, safe, noninvasive and effective method to evaluate intrapulmonary vascular dilatation associated with right-to-left shunts.
Reference
1. Krowaka MJ, Cortese DA. Hepatopulmonary syndrome: current concepts in diagnostic and therapeutic considerations. Chest 1994;47:897-902
2. Kim JH, Park CH, Pai MS, Hahn MH, Kim HJ. Hepatopulmonary syndrome in Gaucher disease with right-to-left shunt: evaluation and measurement using Tc-99m MAA. Clin Nucl Med 1999;24:164-166
3. Lee KN, Lee HJ, Shin WW, Webb WR. Hypoxemia and liver cirrhosis (hepatopulmonary syndrome) in eight patients: comparison of the central and peripheral pulmonary vasculature. Radiology 1999;211:549-553
4. Castro M, Krowaka MJ. Hepatopulmonary syndrome: a pulmonary vascular complication of liver disease. Clin Chest Med 1996; 17:35-48
5. Cremona G, Higenbottam TW, Mayoral V, et al. Elevated exhaled nitric oxide in patients with hepatopulmonary syndrome. Eur Respir J 1995;8:1883-1885
Keywords
Multiple organ, Others,
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