Introduction

Liver is the largest organ of body and about 1.5 kg in average adult human. The basic functional unit of liver is lobule which is cylindrical, several mm in length and 0.8 to 2 mm in diameter. Cirrhosis is the most common condition associated with HPS. The cause of liver disease leading to portal hypertension does not seem to affect the development of HPS. Kennedy et al^1,2 first defined HPS in 1977. HPS is characterized as a triad: liver disease, intrapulmonary vascular dilatation and arterial hypoxemia. HPS has been reported in patients with prehepatic portal hypertensionin the absence of chronic liver disease, in Budd-Chiari syndrome and even in patients with acute or chronic inflammatory liver disease without evidence of cirrhosis or portal hypertension^3-7

The presence of HPS increases mortality in affected patients. No effective medical therapies are available for HPS, although liver transplantation reverses the syndrome in most patients. In clinical studies, the increase of nitric oxide production in the lung plays a role in HPS pathogenesis^8-13. When compared with cirrhotic control patients, exhalation NO levels increase in the cases with cirrhotic HPS.

1. Kennedy TC, Knudson RJ. Exercise-aggravated hypoxemia and orthodeoxia in cirrhosis. Chest 1977; 72: 305-309.
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3. Hoeper MM, Krowka MJ, Strassburg CP. Portopulmonary hypertension and hepatopulmonary syndrome. Lancet 2004; 363: 1461-1468.
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7. Tzovaras N, Stefos A, Georgiadou SP, Gatselis N, Papadamou G, Rigopoulou E, Ioannou M, Skoularigis I, Dalekos GN. Reversion of severe hepatopulmonary syndrome in a non cirrhotic patient after corticosteroid treatment for granulomatous hepatitis: a case report and review of the literature. World J Gastroenterol 2006; 12: 336-339.
8. Strassburg CP. Gastrointestinal disorders of the critically ill. Shock liver. Best Pract Res Clin Gastroenterol 2003; 17: 369-381
9. Zhang HY, Han DW, Wang XG, Zhao YC, Zhou X, Zhao HZ. Experimental study on the role of endotoxin in the development of hepatopulmonary syndrome. World J Gastroenterol 2005; 11: 567-572.
10. Zhang HY, Han DW, Zhao ZF, Liu MS, Wu YJ, Chen XM, Ji C. Multiple pathogenic factor-induced complications of cirrhosis in rats: a new model of hepatopulmonary syndrome with intestinal endotoxemia. World J Gastroenterol 2007; 13: 3500-3507.
11. Vallance P, Moncada S. Hyperdynamic circulation in cirrhosis: a role for nitric oxide? Lancet 1991; 337: 776-778 [PMID: 1706450 DOI: 10.1016/0140-6736(91)91384-7].
12. Fallon MB, Abrams GA, Luo B, Hou Z, Dai J, Ku DD. The role of endothelial nitric oxide synthase in the pathogenesis of a rat model of hepatopulmonary syndrome. Gastroenterology 1997; 113: 606-614.
13. Liu L, Zhang M, Luo B, Abrams GA, Fallon MB. Biliary cyst fluid from common bile duct-ligated rats stimulates endothelial nitric oxide synthase in pulmonary artery endothelial cells: a potential role in hepatopulmonary syndrome. Hepatology 2001; 33: 722-727.
14. Rolla G, Brussino L, Colagrande P, Scappaticci E, Morello M, Bergerone S, Ottobrelli A, Cerutti E, Polizzi S, Bucca C. Exhaled nitric oxide and impaired oxygenation in cirrhotic patients before and after liver transplantation. Ann Intern Med 1998; 129: 375-378.
15. Schroeder RA, Ewing CA, Sitzmann JV, Kuo PC. Pulmonary expression of iNOS and HO-1 protein is upregulated in a rat model of prehepatic portal hypertension. Dig Dis Sci 2000; 45: 2405-2410.

Dr Arun Kumar

Senior Consultant Physician, District Hospital, Jhansi