A 48-year-old woman is evaluated for shortness of breath of 6 weeks' duration. She has cirrhosis due to primary biliary cholangitis.
On physical examination, vital signs are normal. Spider nevi are present on the skin. The cardiopulmonary examination is normal. There is no edema. When the patient is supine, oxygen saturation is 98% breathing ambient air, but oxygen saturation drops to 92% with standing.
A radiograph of the chest is normal.
Which of the following is the most appropriate diagnostic test?
B. CT angiography
C. Echocardiography with agitated saline
D. Pulmonary function testing
MKSAP Answer and Critique
The correct answer is C. Echocardiography with agitated saline. This content is available to MKSAP 18 subscribers as Question 8 in the Gastroenterology and Hepatology section. More information about MKSAP is available online.
Echocardiography with agitated saline is the most appropriate next test for this patient. Hepatopulmonary syndrome is a complication of cirrhosis caused by dilation of the pulmonary vasculature in the setting of advanced liver disease and portal hypertension. A high alveolar-arterial oxygen gradient results from functional shunting. Patients with hepatopulmonary syndrome usually have a preexisting diagnosis of liver disease and present with shortness of breath. Dilation of pulmonary vasculature occurs at the base of the lungs, so hypoxemia is most noted when patients are upright or sitting, when shunting is maximal. Classic features are platypnea (worsening shortness of breath in the upright position) and orthodeoxia (worsening arterial oxygen saturation in the upright position). Pulse oximetry is often used to screen for changes in the arterial oxygen saturation level with changes of position. The diagnosis is made by demonstrating an arterial oxygen tension less than 80 mm Hg (10.7 kPa) breathing ambient air, or an alveolar-arterial gradient of 15 mm Hg (2 kPa) or greater, along with evidence of intrapulmonary shunting on echocardiography with agitated saline or macroaggregated albumin study. The detection of intrapulmonary shunting of blood is best confirmed by echocardiography with agitated saline (also known as a bubble study), during which bubbles are identified in the left side of the heart after 5 beats, demonstrating that the shunting of blood is not intracardiac. Clinically significant hepatopulmonary syndrome is treated with supplemental oxygen and liver transplantation. Hepatopulmonary syndrome is a progressive condition that is ultimately fatal without liver transplantation.
Bronchoscopy is of no value in the diagnosis of platypnea or shunting disorders. It is potentially useful in the diagnosis of a pulmonary infiltrate or relief of an airway obstruction.
CT angiography can demonstrate the presence of large vascular shunts in the lungs but is rarely required to establish the diagnosis of hepatopulmonary syndrome. An additional benefit of CT angiography is its ability to show pulmonary emboli. In this patient, the presence of orthopnea is not consistent with pulmonary embolism. Transthoracic echocardiography with agitated saline is the gold standard for detecting pulmonary vascular dilatation and diagnosing hepatopulmonary syndrome.
Pulmonary function testing is useful for evaluating the presence of obstructive lung disease as well as restrictive lung disease. The normal pulmonary examination and normal chest radiography suggest that neither restrictive nor obstructive lung disease is contributing to this patient's presentation.
- The diagnosis of hepatopulmonary syndrome is made by demonstrating an arterial oxygen tension less than 80 mm Hg (10.7 kPa) breathing ambient air, or an alveolar-arterial gradient of 15 mm Hg (2 kPa) or greater, along with evidence of intrapulmonary shunting on echocardiography with agitated saline or macroaggregated albumin study.