Tehran University of Medical Sciences Case Reports in Clinical Practice 2538-2683 4 1 2019 07 16 5 8 Masoumeh Asgarshirazi Department of Pediatrics, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran. Mehrnoush Ghafarypour Department of Pediatrics, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran. Yahya Aghighi Department of Pediatrics, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran. Seyyedreza Raeeskarami Department of Pediatrics, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran. Mehri Najafi Department of Pediatrics, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran. 2018 09 13 2019 01 28 Ascites is not a usual finding in prehepatic portal hypertension, including portal vein thrombosis, but when portal vein thrombosis is acute and massive, ascites can be a presenting feature. We report a 9-year-old boy with tense ascites and portal and superior mesenteric vein thrombosis. A 9-year-old boy was evaluated for tense ascites which led to umbilical hernia since one month before admission. He did not have any clinical or laboratory stigmata of parenchymal liver disease. Imaging studies showed superior mesenteric and portal vein thrombosis. In laboratory tests for pre-thrombotic states, he suffered from significant protein S deficiency. Thrombophilic states like protein S deficiency predispose patient to vascular thrombosis. This vascular thrombosis can be present with signs and symptoms related to their territories. Prevention of thrombosis and rethrombosis with anticoagulant therapy is recommended. https://crcp.tums.ac.ir/index.php/crcp/article/view/220 https://crcp.tums.ac.ir/index.php/crcp/article/download/220/288