Grey Turner's sign refers to the bruising around the flanks (the sides of the body between the ribs and the hips), which is commonly associated with severe acute pancreatitis. This sign is a result of retroperitoneal hemorrhage, which can occur due to the inflammation and necrosis of the pancreas.
In the case of severe acute cholecystitis, acute cholangitis, and acute hepatitis, this sign is not commonly seen.
Thus, the correct answer is Severe Acute Pancreatitis.