Retroperitoneal hemorrhage (or retroperitoneal hematoma) refers to an accumulation of blood found in the retroperitoneal space. It can present with Grey Turner's sign (flank bruising). Causes include: 1  anticoagulation. 2  a ruptured aortic aneurysm. 3  a ruptured renal aneurysm. 4  acute pancreatitis. 5  malignancy.