Last Week's Medical Mystery

 

This 50-year-old man presents with platypnea and orthodeoxia. What is your diagnosis and what test would you order for confirmations?

lung scan  brain uptake HPS patient

Diagnosis: Hepatopulmonary syndrome (HPS). Patients with long-standing cirrhosis and portal hypertension are prone to develop HPS, defined by the triad of cirrhosis, hypoxemia, and pulmonary arteriovenous shunting. HPS symptoms include platypnea and orthodeoxia, representing shortness of breath and arterial desaturation on assuming an erect position. Vasodilators entering the portal circulation normally screened out by the liver gain access to the pulmonary circulation, dilating pulmonary capillaries to the extent that the core of the capillary blood stream is too distant from the alveolar-capillary interface to be oxygenated - in effect creating a right-to-left shunt (thus the cyanosis and clubbing seen in this medical mystery patient). A safe and cost effective method to confirm the diagnosis of a right-to-left shunt is to perform a ventilation-perfusion scan and demonstrate 6% or greater uptake of the radioisotope by the brain; normally, the majority of the labeled albumin is removed during its passage through the pulmonary circulation. Unfortunately, the prognosis in HPS is poor.

Above: the left picture is this patient's lung scan.The middle picture demonstrates abnormal isotope uptake by his brain, confirming the presence of a  right-to-left shunt.