The utility of the macro-aggregated albumin lung perfusion scan in the diagnosis and prognosis of hepatopulmonary syndrome in cirrhotic patients candidates for liver transplantation

Hepatopulmonary Syndrome: A Comprehensive Review

Hepatopulmonary syndrome (HPS) is defined by abnormally dilated blood vessels and shunts within the lungs, leading to impaired oxygen exchange. This condition results from intricate interactions between the liver, the gastrointestinal system, and the lungs. This complex system primarily affects pulmonary endothelial, immunomodulatory, and respiratory epithelial cells. Consequently, this contributes to pathological pulmonary changes characteristic of HPS. A classification system based on the severity of oxygen deficiency has been proposed for grading the physiological dysfunction of HPS. Contrast-enhanced echocardiography is considered the primary radiological evaluation for identifying abnormal blood vessel dilations within the lungs, which, combined with an elevated alveolar-arterial gradient, is essential for making the diagnosis. Liver transplantation is the sole effective definitive treatment that can reverse the course of the condition. Despite often being symptomless, HPS carries a significant risk of mortality before transplantation, regardless of the severity of liver disease. Meanwhile, there is varying data regarding survival rates following liver transplantation. The adoption of the model for end-stage liver disease (MELD) standard exception policy has notably improved the results for individuals with HPS compared to the period before MELD was introduced. This review offers a summary of the present understanding, highlighting recent advancements in the diagnosis and treatment of HPS. Furthermore, it aims to augment comprehension of the condition's fundamental mechanisms through insights derived from experimental models and translational research.

Advances in Diagnostic Imaging of Hepatopulmonary Syndrome

Hepatopulmonary syndrome (HPS) is a serious pulmonary complication of progressive liver disease that leads to a poor clinical prognosis. Patients with HPS may develop acute respiratory failure, which requires intensive care and therapy. At present, the only effective treatment is liver transplantation; therefore, early diagnosis and timely treatment are of considerable significance. The three main features of HPS are liver disease, oxygenation disorder, and intrapulmonary vascular dilatation (IPVD). Diagnosing HPS is challenging due to the difficulty in detecting the presence or absence of IPVD. As such, imaging examination is very important for detecting IPVD. This paper reviews the imaging methods for diagnosing HPS such as ultrasound, dynamic pulmonary perfusion imaging, pulmonary angiography, and computed tomography.

Hepatopulmonary Syndrome with Right-to-left Shunt in Cirrhotic Patients Using Macro-Aggregated Albumin Lung Perfusion Scan: Comparison with Contrast Echocardiography and Association with Clinical Data

Objectives:

The diagnosis of hepatopulmonary syndrome (HPS) which is a common complication in cirrhotic patients is still subject to debate. This study investigated the association of clinical findings with HPS in cirrhotic patients using macro-aggregated albumin lung perfusion scan (^99mTc-MAA lung scintigraphy). In addition, comparison between ^99mTc-MAA lung scintigraphy and contrast echocardiography (CEE) in detection of HPS was also performed.

Methods:

In this study, 27 patients with cirrhosis underwent ^99mTc-MAA lung scintigraphy and contrast echocardiography comparison CEE and the frequency of HPS was assessed in them and also was compared across the other variables.

Results:

The ^99mTc-MAA lung scintigraphy showed HPS in 13 patients (48.1%) while CEE demonstrated HPS in 5 patients with cirrhosis (18.51%). HPS was mild in 40.74% (11/27) of the patients, and severe in only 2 patients. There was no relationship between gender, disease duration, having diagnosis of disease previously, pulmonary symptoms and Child-Pugh score variations and HPS (p>0.05). Comparison of hemodynamic indices, arterial blood gas analysis and laboratory indices between patients with and without HPS was also non-significant (p value >0.05). Among coagulation factors assessed in cirrhotic patients, we found only significant correlation between HPS and prothrombin time (p<0.05).

Conclusion:

HPS, particularly its mild form, is noted in a great number of patients with cirrhosis using 99mTc-MAA lung scintigraphy. Because of its technical ease, and possibility to obtain objective quantitative information, ^99mTc-MAA lung scintigraphy can be complementary to other diagnostic methods in the evaluation of HPS assessment, although additional studies are needed.