宮崎 都志幸, 塩谷 英之, 松永 公雄

Toshiyuki MIYAZAKI, Hideyuki SHIOTANI, Kimio MATSUNAGA

兵庫県立成人病センター内科

Department of Internal Medicine, Hyogo Medical Center for Adults

キーワード : Liver cirrhosis, Hypoxemia, Pulmonary shunt, Contrast echocadiography

A case of liver cirrhosis associated with abnormal pulmonary shunt was confirmed by contrast echocardiography. The patient, a 52-year-old female, had been treated for chronic hepatitis for 6 years, and had noticed dyspnea on effort, cyanosis, and clubbing of fingers for 4 years. Laboratory findings and ultrasonography of the abdomen suggested liver cirrhosis. The arterial blood gas data showed marked hypoxemia (PaO₂; 43.8 mmHg). A chest X-ray, electrocardiography, echocardiography, and cardiac catheterization ruled out heart desease. The chest X-ray showed decreased air in the middle and lower lobes of the right lung, and respiratory function tests revealed abnormal %DLco (34.3%) and, ΔN₂% (2.66%). However, these findings alone were not sufficient to explain the severe hypoxemia. The pulmonary per fusion image with ^99mTc-MAA revealed significant uptake in the brain, liver, and spleen, while ruling out a massive blood flow defect in the lungs. To confirm the intrapulmonary abnormal shunt suggested by the pulmonary per fusion image with ^99mTc-MAA, contrast echocardiography was performed by infusing saline rapidly into the left antecubital vein. After the injection, the right ventricle was opacified, but the left heart chambers were free of contrast until 3 cardiac cycles later when contrast was seen to enter the left atrium and left ventricle. Normally, contrast is cleared after passing through normal pulmonary capillaries, so the appearance of contrast in the left heart chambers is abnormal and indicates the presence of connection bypassing the capillaries. Shunting at the intracardiac level can be ruled out by a delay in the apperance of contrast in the left heart chambers. This delay, usually 2-3 cardiac cycles, represents the time taken for the contrast to pass through the intrapulmonary abnormal connections.
Severe hypoxemia accompanying liver cirrhosis is probably caused by several factors, of which abnormal pulmonary shunt may be an important one. In detecting this abnormal shunt, contrast echocadiography is a useful test as it is a sensitive, non-invasive, and non-radioactive technique.