<prompt> Commonest cause of Budd Chiari syndrome is?Valve in the IVCHepatocellular carcinomaParoxysmal nocturnal hemoglobinuriaRenal cell carcinoma  <response>: Answer is C Paroxymal nocturnal hemoglobinuria PsH is the most common cause of iSudd Chiral syndrome amongst the options provided. Most common cause of Budd chiari syndrome is - thrombosis of hepatic veinQ This is seen in the setting of : - polycythemia rubra veraQ - myeloproliferative syndromeQ - Paroxysmal nocturnal hemoglobinuriaQ - Oral contraceptive use - Hyercoagulable states It may also result from obstruction of venacava.Q This may be seen in the setting of : - invasion of IVC by tumor such as hepatocellular carcinoma. - Idiopathetic membranous obstruction of IVC is the most common cause of this syndrome in Japan. 