The aim of this book is not introduce readers “how to diagnose and treat HPS” or provide the established practice guidelines about HPS. Instead, it is about the problems and next directions that we should focus on in the research of HPS. Another motivating force for writing this book is to provide the younger generation with available history of HPS research and then make them quickly acquiring a large amount of data. The research of HPS has only underwent several decades, many basic questions about the pathophysiology, diagnosis and treatment of the HPS need to be disclosed.

Questions about pathophysiology include the following:

1. What is the mechanism of IPVD? More specifically, what are the specific humoral mediators produced in liver lead to the development of HPS, and what are their precise mechanisms?

2. Is angiogenesis an important pulmonary alteration in human HPS? Are there any uncovered pathological alterations in human HPS?

Questions about diagnosis include the following:

1. What are the appropriate diagnosis standards to defne HPS?

2. Contrast-enhanced echocardiography, 99mTcMAA perfusion scanning and high resolute chest CT, which is the best diagnosis tool for HPS? How to improve their sensitivity and specifcity in diagnosing HPS?

3. How to identify HPS in the early stage?

4. What is the significance of the detection of anatomical intrapulmonary shunt without associated hypoxemia? Do patients with this condition would develop hypoxemia, and are there identifable clinical manifestation that can help clinicians identify such patients?

Questions about treatment include the following:

1. The broad scale research about HPS is defcient, multicenter studies or a national register studies will be required to completely assess the effects of the available strategies in treat HPS and to identify which patients are likely to respond to such treatment.

2. There are no available pharmacologic and nonsurgical treatments to cure HPS, further studies are needed to provide other options.

3. The reversal effects of the HPS after liver transplantation are different, so making clear the predictors of reversal, time to resolution and mechanisms of reversal are necessary.