Question category: Gastroenterology
A 43 year old male was in a road traffic accident and suffered major trauma. He is now in the intensive care unit. He has become pyrexial and he appears to be in pain. On examination he appears to be tender in the right upper quadrant. Bloods reveal deranged LFTs and his amylase is also elevated. He also has a leucocytosis. An ultrasound reveals a distended gallbladder with thickened walls and pericholecystic fluid although there is no evidence of gallstones. What is the most likely diagnosis?