A wide variety of chest complications can occur in patients with chronic liver disease. A common one is mild hypoxemia, with 18% of patients with liver disease experiencing respiratory distress. The liver has important interactions with every organ system, including the cardiovascular and pulmonary systems, and plays an important role in maintaining intraorgan environmental stability and metabolism. Decreased hepatic clearance or increased products of circulating cytokines and vascular growth regulators can cause pulmonary complications. These affect the pulmonary vasculature and cause a systemic inflammatory response. Mechanical factors can also cause thoracic complications. For example, increased abdominal pressure and ascites elevates the septum causing respiratory distress. Migration of ascites from the peritoneal cavity to the pleural cavity via a diaphragmatic defect causes hepatic pleural fluid. The clinical manifestations of infection and response to treatment vary in patients with chronic liver disease due to the compromised host immune system. This article examines the thoracic complications of chronic liver disease and the abnormal effects on cardiopulmonary function. Specifically, we discuss hepatopulmonary syndrome, portal pulmonary hypertension, intrathoracic portal collateral vessels, hepatic pleural fluid, acute respiratory distress syndrome (ARDS), pulmonary infections, intrapulmonary manifestations of hepatocellular liver cancer (HCC), and drug-induced diffuse interstitial lung disease. Hepatopulmonary syndrome Hepatopulmonary syndrome is defined as stage III liver disease with increased differential alveolar arterial partial pressure of oxygen and intrapulmonary vasodilation (while breathing room air). It is seen in 15-20% of patients with liver cirrhosis. The clinical manifestation of hepatopulmonary syndrome is progressive dyspnea, cyanosis and pestle finger in patients with cirrhosis. The mechanism of hepatopulmonary syndrome is an excess of vasodilatation products, especially NO, underlying vasodilation. Pathologically, intrapulmonary vasodilatation is manifested by anterior capillary dilation, arteriovenous shunts and pleural vasodilation. Anterior capillary dilatation is associated with specific ventilatory hyperperfusion (excess perfusion for a given ventilation) (ventilation-perfusion dysregulation), diffusion limitation (incomplete oxygen penetration through adjacent alveolar dilated vessels), and true anatomic shunts (direct mixing of arteriovenous blood without gas exchange). The presence of dilated intrapulmonary vessels and arteriovenous shunts can be confirmed by cardiac ultrasound (acoustic) imaging, 99mTc-labeled polymerized albumin scans, or pulmonary arteriography. There are two types of pulmonary angiographic findings in hepatopulmonary syndrome. type I is the most common (86% of cases) and presents as subpleural capillary dilation with distal vascularization; CT signs include multiple, mildly dilated subpleural vessels that do not taper normally at one end and extend to the pleural surface. type II hepatopulmonary syndrome (14% of cases) is characterized by distinctive arteriovenous malformations on angiography and peripleural pulmonary vessels on CT scan. The type II hepatopulmonary syndrome (14% of cases) is characterized by distinctive arteriovenous malformations on angiography and nodular dilatation of peripleural pulmonary vessels on CT scan. The typical presentation of hepatopulmonary syndrome on plain radiographs is basal, moderate-sized nodules, or a reticular nodular shadow. Portal pulmonary hypertension Portal pulmonary hypertension is the development of pulmonary hypertension on top of portal hypertension. The incidence of portal pulmonary hypertension in patients with cirrhosis is 2-5%. The recommended diagnostic criteria for portal pulmonary hypertension are a mean pulmonary artery pressure greater than 25 mmHg at rest, increased pulmonary vascular resistance, pulmonary capillary wedge pressure less than 15 mmHg, and manifestations of portal hypertension. There are three presumed mechanisms of pulmonary hypertension due to portal hypertension. First, vasoactive substances, such as serotonin, interleukin-1, endothelin-1, and thromboxane, can cause pulmonary vasoconstriction and pulmonary artery mitogenesis, which the liver is unable to remove efficiently via the portal shunt bypass or the diseased liver. Second, venous thromboembolism leads to portal pulmonary hypertension, such that clots from portal or other systemic sources reach the pulmonary circulation via a portal shunt and cause pulmonary hypertension. Finally, high cardiac output is associated with cirrhosis exposes the pulmonary vascular bed to increased shear stress, causing vasoconstriction, hypertrophy, and pulmonary vascular endothelial cell proliferation. Early chest radiographic findings may be normal, but progressive disease causes protrusion of the central pulmonary artery, dramatic thinning of the peripheral vasculature, and enlargement of the right ventricle. patients under 50 years of age. All causes of pulmonary hypertension are shown on high-resolution CT as a mosaic pattern of lung attenuation with (high and low) density in the lungs, a relatively specific manifestation of thromboembolic pulmonary hypertension. Radionuclide lung perfusion scans may be normal or may show diffuse patchy perfusion defects in patients with severe pulmonary hypertension. Intrathoracic portal collateral vessels Portal hypertension produces a large number and wide range of portal collateral pathways with diverse manifestations. The typical intrathoracic manifestation of these spontaneous portal collateral vessels is through the coronary veins into the esophagus (80-90%) or paraesophageal (22-38%) veins and septal angle veins (18%). Esophageal veins are the most common and clinically important collateral vessels, consisting of dilated subcutaneous and submucosal veins in the lower esophageal wall. CT is used to detect and grade esophageal varices and has a detection rate of more than 90% for clinically significant cases.CT shows nodular thickening of the esophageal wall and enhanced nodular lesions protruding into the esophageal lumen.CT esophagography CT esophagography is used for screening to identify high or low risk of varices. X-rays show paraoesophageal varices projecting to the side of the paraspinal division and loss of the division between the odd vein esophageal saphenous and descending aorta CT shows dilated collateral vessels around the thoracic segment of the esophagus and descending aorta. The septal angle varices consist of dilated parasternal veins and are commonly seen in patients with cirrhosis due to membranous obstruction of the inferior vena cava (IVC). x-ray shows wavy nodules at the edge of the heart that resemble tumors. ct-enhanced scans easily show the vascular nature of the pseudotumor. Hepatic pleural fluid Hepatic pleural fluid is a large amount of pleural fluid, often greater than 500 ml, seen in patients with cirrhosis without cardiopulmonary disorders. It is a relatively uncommon complication of end-stage liver disease, with an estimated incidence of 5-10% in patients with cirrhosis. The most widely accepted theory explaining its pathophysiology is the leakage of ascites through the diaphragmatic defect. The pressure difference acts to drive fluid from the peritoneal cavity into the pleural cavity; therefore, hepatic pleural fluid is occasionally seen in those without ascites. Hepatic pleural fluid is most often seen on the right side (85%), occurs on the left side in 13% of cases and bilaterally in 2% of cases. A variety of respiratory symptoms can occur, including dyspnea, non-irritating cough, (pleuritic) chest pain, and fatigue due to oxygen deficiency, but respiratory failure is rare in patients with acute tension pleural fluid. Diagnostic thoracentesis should be performed in all patients suspected of having hepatic pleural fluid. A recent study has shown that apart from the occurrence of pleural fluid in 30% of patients with cirrhosis, a pleural fluid analysis during the first diagnosis can yield a diagnosis. Chest CT is used to rule out pulmonary, mediastinal or pleural disease. Treatment includes diuretics, therapeutic thoracentesis, transjugular intrahepatic portosystemic shunts, and surgical treatment may be considered, including placement of a thoracotomy and injection of sclerosing agents, surgical treatment of a transverse septal defect, and abdominal vena cava shunts. Acute respiratory distress syndrome (ARDS) The presence of cirrhosis (a comorbidcondition) influences the occurrence and severity of ARDS and is associated with a poor prognosis. There is a growing recognition that the understanding and determination of ARDS should take into account organ interactions, although these interactions are difficult to understand. The liver plays an important role in regulating the kinetics of cytokines associated with acute lung injury. Altered hepatic blood flow or cellular uptake causes a systemic “spillover” of pro-inflammatory response substances that impair the filtration function of the liver, making severe hepatic dysfunction itself an important risk factor for acute lung injury and ARDS. When acute lung injury occurs under these conditions, the subsequent clinical course may be unusually severe or prolonged. A recent study of 29 patients with end-stage liver failure showed a higher incidence of ARDS (79%) than randomized controls in the intensive care unit (6.8%). Doyle et al. reported a higher mortality rate of acute lung injury in 26 patients with chronic liver disease than in those without liver disease. The early radiographic presentation of ARDS is patchy shadows followed by diffuse solid lesions on both sides during the exudative and proliferative phases. ARDS tends to be a heterogeneous mixture of ground glass density and solidity due to its pulmonary origin. Infection Infection is a serious and often fatal complication in patients with chronic liver disease. Abnormalities in cellular and humoral immunity and the increasing number of invasive procedures such as transjugular intrahepatic portosystemic shunts or thoracentesis make these patients susceptible to a wide variety of bacterial, fungal, and viral infections. The most common bacterial infections include bacteremia, pneumonia, urinary tract infections, and idiopathic bacterial peritonitis. Pneumonia is seen in approximately 21% of patients with cirrhosis, and the most common pathogen is Streptococcus pneumoniae, with a mortality rate of 41%. The increased mortality in these patients with pneumococcal pneumonia is associated with a deficiency of neutrophils that regulate the killing of pneumococci in the lungs. In alcoholic cirrhosis, special attention is paid to anaerobic infections, Haemophilus infections, and Klebsiella infections. Idiopathic bacterial pustulosis is an infection of pre-existing pleural fluid with a reported incidence of 13% in cirrhotic patients with confirmed pleural fluid, although the pathogenesis is not fully understood, there is a hypothesis that intestinal microorganisms reach (infection reaches) the pleural fluid through bacteremia. Mycobacterium tuberculosis infection presenting as extrapulmonary tuberculosis is more common in patients with cirrhosis, but the clinical and imaging manifestations and response to treatment are no different than in patients without cirrhosis. Intrathoracic manifestations of hepatocellular carcinoma (HCC) Cirrhosis due to any chronic liver disease predisposes to HCC. the highest incidence of progression of underlying (underlying) cirrhosis to HCC is seen in viral hepatitis C infection (HCC incidence 17-30%), followed by hereditary hemophilia (21%), viral hepatitis B infection (10%-15%), alcoholic cirrhosis （Intrathoracic manifestations of HCC vary, with the most common intrathoracic manifestation of HCC being multiple pulmonary nodules due to hematogenous metastases. Less common forms include mediastinal lymph node enlargement, pulmonary tumor emboli, and tumor invasion of the IVC and right atrium; the latter may be the initial manifestation of HCC. Cavoatrial tumors spread, occasionally with pulmonary embolism, and may appear as neoplastic tumors in locations below the patient’s diaphragm, such as the liver, kidneys, adrenal glands, blood vessels, and genital tract. (Occasionally with pulmonary embolic events, may occur in patients with a neoplasm arising in infradiaphragmatic sites) Kojiro et al. reported HCC spread to the hepatic vein or IVC in 7.5% and 4% of the right atrium. The tumor enters the right atrium and intermittently obstructs the tricuspid valve, resulting in decreased cardiac output and sudden death of the patient. Enhanced CT clearly shows hypodense nodules by intrahepatic invasion of the hepatic veins, IVC, and right atrium, and hypodense emboli in the pulmonary artery. Magnetic resonance imaging (MRI) and fluorodeoxyglucose positron emission imaging help to identify intravascular tumors and thrombi, as shown by gadolinium contrast enhancement or tumor uptake of radionuclides. Drug-induced diffuse interstitial lung disease Nodular disease is a rare pulmonary complication of chronic viral hepatitis C infection treated with interferon; it can be the initial presentation or a reactivation of a pre-existing nodular disease during or shortly after treatment. Interferon is used to treat a variety of malignant or non-malignant (benign) diseases, commonly viral hepatitis C. Various side effects include causing or exacerbating autoimmune phenomena, which may be related to its complex immunomodulatory nature. Although the exact mechanism by which interferon causes nodulopathy is unknown, there is a hypothesis that macrophage activation is associated with the granuloma formation that triggers the histology typical of nodulopathy. The nodular disease associated with interferon therapy mainly presents as benign lesions of the lung or skin with a simple evolution. Imaging features include enlarged hilar and paratracheal lymph nodes on both sides of the lungs, and high-resolution CT shows multiple nodules along the lymphatic vessels in both lungs. Sharma et al. reported a 14% incidence of interstitial pneumonia in patients with primary biliary cirrhosis treated with low-dose methotrexate. Methotrexate-induced lung injury is shown on chest radiographs as exudates at the base of both lungs. In acute cases, CT shows diffuse and patchy areas of ground glass density shadow or solid shadow, and poorly defined lobular central nodules, which diminish with methotrexate withdrawal or treatment with corticosteroids; however, those who develop pulmonary fibrosis have a poor prognosis. Conclusion Patients with cirrhosis and portal hypertension present with typical pulmonary hemodynamic changes caused by hepatopulmonary syndrome or portal hypertension. Hepatopulmonary syndrome is characterized by intrapulmonary vasodilation and arteriovenous shunts. Various intrathoracic portal collateral vessels, including esophageal, paraesophageal, and septal angle varices, are common and appear tumor-like on chest radiographs. Hepatic pleural fluid, with leakage of ascites through the diaphragmatic defect, may progress even after the ascites disappears. Chronic liver disease is associated with an increased incidence and severity of ARDS and a poor prognosis. Immunocompromise and invasive procedures predispose these patients to a variety of infections. hcc is a common complication of cirrhosis, manifested by various intrathoracic metastases such as multiple pulmonary nodules, mediastinal lymph node enlargement, or pulmonary tumor embolization associated with atrial tumor spread. Nodular disease induced by interferon therapy in patients with chronic viral hepatitis C presents with pulmonary lesions with perilymphatic distribution and enlarged hilar and mediastinal lymph nodes in both lungs.