A 7 year old girl from Bihar presented with three episodes of massive hematemesis and melena. There is no history of jaundice. On examination, she had a large spleen, non-palpable liver and mild ascites. Portal vein was not visualized on ultrasonography. Liver function tests were normal and endoscopy revealed esophageal varices. The most likely diagnosis is –

Differentiation between Extrahepatic and Hepatic / Post hepatic portal hypertension Post sinusoidal and hepatic causes of portal hypertension will have evidence of Liver parenchymal damage / deranged LFT (jaundice) a dilated portal vein on ultrasonography Extrahepatic presinusoidal obstruction will not have any effect on the Liver and hence there will be no evidence of hepatocellular damage. No jaundice / No raised deranged LFT Also non visualization of portal vein is a characteristic of portal vein thrombosis, an Extrahepatic cause. Esophageal varices and splenomegaly are a manifestation of portal hypertension and will be present in all the above sites of obstruction.