Grey Turner's sign refers to bruising of the flanks. The bruising appears as a blue discoloration,[and is a sign of retroperitoneal hemorrhage, or bleeding behind the peritoneum, which is a lining of the abdominal cavity. Grey Turner's sign takes 24–48 hours to develop, and can predict a severe attack of acute pancreatitis. Grey Turner's sign may be accompanied by Cullen's sign. Both signs may be indicative of pancreatic necrosis with retroperitoneal or intra-abdominal bleeding.