Use of a Microbubble Contrast Agent in the Evaluation of Cirrhotic Patients for Hepatopulmonary Syndrome: Preliminary Assessment of a Novel Technique

Hepatopulmonary syndrome (HPS) may cause profound symptomatic hypoxia in patients with chronic liver disease and can be an indication for liver transplantation. The diagnosis relies on the demonstration of intrapulmonary vascular dilatation (IVD) using either contrast-enhanced echocardiography or macro-aggregated lung perfusion scans. We sought to evaluate whether a novel technique using the microbubble agent, Echovist® (Schering AG) with Doppler intensitometry of the carotid artery would be able to identify patients who fulfilled the criteria for HPS. Contrast studies were performed in 18 patients with cirrhosis, examined in the supine and upright positions. Following injection of Echovist, continuous scanning of the common carotid was performed using grey-scale and spectral Doppler for 60 s. Positive studies were determined by online signal analysis of the Doppler signal (crackle-count). Supine and upright pulse oximetry was recorded on all patients, and formal lung function tests where clinically indicated. Two patients met the criteria for HPS. They had positive results on supine and upright scans, with an increased crackle-count when upright. Two patients had single, weakly positive results with normal pulse oximetry. No association was seen between a positive contrast study and the severity of liver disease. Contrast-enhanced carotid Doppler intensitometry is a relatively simple, non-invasive test that may help identify patients with IVD. Comparison with an established technique will be required in future trials to determine its accuracy and assess whether the crackle-count can reliably quantify the degree of IVD.