Advances in Diagnostic Imaging of Hepatopulmonary Syndrome

Diagnostic Potential of 99mTc-macroaggregated Albumin Scintigraphy in the Diagnosis of Hepatopulmonary Syndrome: Insights from Two Case Studies and Critical Review of Literature

Hepatopulmonary syndrome (HPS) is a rare pulmonary vascular complication of chronic liver disease characterized by dilatation of pulmonary capillaries leading to vascular shunting and systemic hypoxemia. Diagnosis of HPS requires documentation of intrapulmonary vasodilation (IPVD), the two most common imaging studies performed for the detection of IPVD include transthoracic contrast echocardiography (TTCE) and 99m-Tc-macroaggregated albumin scintigraphy (99mTc-MAA scan). TTCE has high sensitivity and thus, is the preferred initial investigation, while 99mTc-MAA scan is highly specific and plays an adjuvant role in diagnosis. 99mTc-MAA scan can, however, identify some cases of HPS not apparent on TTCE and can also quantify the shunt fraction. The current study describes the utility of 99mTc-MAA scan in the detection of IPVD in two suspected cases of HPS.

Hepatopulmonary Syndrome Diagnosis in the ICU: The Relevance of Bedside Contrast Saline Echocardiography

Hepatopulmonary syndrome (HPS) is an underdiagnosed complication of chronic liver disease (CLD) characterised by the presence of hypoxaemia due to intrapulmonary vascular dilatations. We present two cases of HPS diagnosed during their stay in the ICU. Both patients had a medical history of alcoholic CLD with portal hypertension (PH). The first patient was transferred to the ICU for acute hypoxic respiratory failure (AHRF) due to decompensated cirrhosis with large-volume hydrothorax and diagnosis of acute-on-chronic liver failure (ACLF) grade 2. The presence of orthodeoxia, an alveolar-arterial oxygen gradient (O2 A-a grad) of 27 mmHg and positive contrast saline echocardiography confirmed the HPS diagnosis. The second patient was transferred to our general ICU from the surgical ward where he was initially admitted with mild AHRF due to polytrauma conditioning left side rib fractures and a small contusion in the left inferior lobe. Upon ICU admission, he was diagnosed with septic shock (nosocomial pneumonia as the primary site of infection) and required invasive mechanical ventilation. During the initial period of his ICU stay, although an improvement in multiple organ dysfunction was observed, severe AHRF persisted. Moreover, O2 A-a grad of 30 mmHg and positive bedside contrast saline echocardiography confirmed the HPS diagnosis. In this study, we discuss the diagnostic approach of HPS and the increasing relevance of contrast saline echocardiography at the bedside, particularly in critically ill patients. The performance of this technique by trained intensivists at the bedside in the ICU minimises critical moments, such as the time required for intra-hospital transport of patients for complementary examinations, considering they have severe ventilatory compromise, thereby allowing HPS diagnosis with high sensitivity.

Pulmonary Assessment of the Liver Transplant Recipient

Respiratory symptoms and hypoxemia can complicate chronic liver disease and portal hypertension. Various pulmonary disorders affecting the pleura, lung parenchyma, and pulmonary vasculature are seen in end-stage liver disease, complicating liver transplantation (LT). Approximately 8% of cirrhotic patients in an intensive care unit develop severe pulmonary problems. These disorders affect waiting list mortality and posttransplant outcomes. A thorough history, physical examination, and appropriate laboratory tests help diagnose and assess the severity to risk stratify pulmonary diseases before LT. Hepatopulmonary syndrome (HPS), portopulmonary hypertension (POPH), and hepatic hydrothorax (HH) are respiratory consequences specific to cirrhosis and portal hypertension. HPS is seen in 5-30% of cirrhosis cases and is characterized by impaired oxygenation due to intrapulmonary vascular dilatations and arteriovenous shunts. Severe HPS is an indication of LT. The majority of patients with HPS resolve their hypoxemia after LT. When pulmonary arterial hypertension occurs in patients with portal hypertension, it is called POPH. All other causes of pulmonary arterial hypertension should be ruled out before labeling as POPH. Since severe POPH (mean pulmonary artery pressure [mPAP] >50 mm Hg) is a relative contraindication for LT, it is crucial to screen for POPH before LT. Those with moderate POPH (mPAP >35 mm Hg), who improve with medical therapy, will benefit from LT. A transudative pleural effusion called hepatic hydrothorax (HH) is seen in 5-10% of people with cirrhosis. Refractory cases of HH benefit from LT. In recent years, increasing clinical expertise and advances in the medical field have resulted in better outcomes in patients with moderate to severe pulmonary disorders, who undergo LT.