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What is A 12-year-old boy presents with hematemesis, Malena and mild splenomegaly. There is no obvious jaundice or ascites. The most likely diagnosis is and explain in detail?
Extra Hepatic Portal Venous Obstruction

5-6 years of age
hematemesis with or without melena
splenomegaly depends on duration of blockage
liver usually normal in size
ascites is rare
variable extent of growth retardation is seen