Retroperitoneal hemorrhage is a somewhat uncommon but potentially life-threatening event. It can develop after an external injury to the abdomen, or as a result of various intrinsic conditions of neoplastic, iatrogenic, or autoimmune origin, in which case the term spontaneous retroperitoneal hemorrhage is used. The severity of symptoms depends on the extent of bleeding, but abdominal pain, shock, and a poor general condition are usually noted. Imaging studies are necessary to confirm the diagnosis.
A rare complication of numerous diseases and external factors, retroperitoneal hemorrhage is defined as sudden bleeding into the retroperitoneal space  and must be recognized early because of its life-threatening nature. In general, conditions that can induce bleeding in the retroperitoneum are broadly divided into two categories - traumatic and spontaneous . Mechanical damage to the visceral structures (both solid and hollow organs), major blood vessels, or musculoskeletal tissues is readily observed in severe trauma (crush injuries, motor vehicle accidents, falls, severe fractures, etc.), and up to 12% of blunt-trauma patients were diagnosed with retroperitoneal hemorrhage in isolated case series  . On the other hand, several authors have documented the appearance of spontaneous retroperitoneal hemorrhage due to an array of intrinsic diseases     . Neoplastic processes (primarily of renal origin, such as renal cell carcinoma, angiomyolipoma, but also pheochromocytoma, hemangioma, paragangliomas, etc.), drugs (anticoagulants - coumadin, low molecular dose heparin), nephritis, polyarteritis nodosa (PAN) and vascular malformations have been confirmed as underlying causes of spontaneous retroperitoneal hemorrhage   . The clinical presentation depends on the severity and rate of blood loss and accumulation in the peritoneum and on the presence of additional injuries . The most common symptoms are an abdominal pain (particularly flank pain), hematuria, and a state of shock  , as blood loss universally leads to hypotension and hypovolemia.
The nonspecific symptomatology of a retroperitoneal hemorrhage may present as a challenge for the physician, which is why a proper diagnostic workup must be conducted. A detailed patient history should define the onset and progression of symptoms, detect if any underlying disorders are present, and confirm if any drugs were recently used (especially anticoagulants). A comprehensive clinical examination is the next step, with an emphasis on abdominal palpation and vital sign assessment. As soon as clinical suspicion toward a bleeding disorder is raised, imaging studies, the key step in recognizing retroperitoneal hemorrhage, should be employed. Plain radiography is of limited benefit in evaluating bleeding disorders (although a degree of haziness in the lower abdomen that can be detected by this method might suggest bleeding), which is why ultrasonography (US) is a preferred first-line method . Ascites, organ contusions and hyperechoic masses in the retroperitoneum are signs of retroperitoneal hemorrhage on US . The use of contrast-enhanced computed tomography (CT) is recommended when ultrasonography and clinical findings point toward retroperitoneal bleeding, as it can delineate the exact location of bleeding, but also confirm damage to the viscera and major blood vessels   .