Retroperitoneal Hematoma

Etiology

In the setting of traumatic retroperitoneal hematoma, the mechanism of injury can be broken down into blunt or penetrating. Blunt trauma comprises the majority of retroperitoneal hematomas seen in practice and, by definition, is the result of a transfer of energy from an outside source to the patient. The blunt mechanism results in compressive and deceleration forces, often crushing and shearing injuries to tissues and vascular structures. Examples of blunt force injuries include perirenal hematomas, pancreatic injuries, pelvic retroperitoneal hematomas as a result of pelvic fractures and disruption of nearby vascular structures, and direct avulsion injuries to blood vessels within the retroperitoneum. Penetrating trauma leading to retroperitoneal hematoma is commonly the result of lower energy mechanisms such as gunshot wounds or stabbings. Injuries associated with penetrating trauma depend on specific organs or vessels affected by the penetrating object's trajectory. Many of these penetrating injuries will have concomitant injuries within the peritoneal cavity.[3][5]

Retroperitoneal hematomas that occur outside the setting of trauma are either spontaneous or iatrogenic in etiology. Iatrogenic retroperitoneal hematomas are the result of percutaneous interventions or endovascular procedures. While the literature demonstrates that this is a rare complication, the occurrence of associated morbidity and mortality are high. Rates of percutaneous intervention-associated retroperitoneal hematomas are on the decline, with one 2018 study citing an incidence of 0.06%. This low incidence, however, was juxtaposed with a 3.5-fold independent increase in 30-day mortality. Risk factors for retroperitoneal hematoma following percutaneous interventions appear to be arterial puncture above the level of the inguinal ligament, female sex, and being treated with GPIIb/IIIa inhibitors or warfarin.[6][7][8]

Spontaneous retroperitoneal hematoma is relatively rare, with a high degree of morbidity and mortality. Much of the literature on the subject is limited to case series and retrospective cohort studies. Trends in the data surrounding spontaneous retroperitoneal hematoma suggest that this diagnosis is more common in older adults, patients receiving anticoagulation therapy, and those with underlying coagulopathy. Recently, several cases of patients with COVID-19 have been reported.[9] While most patients with retroperitoneal hematomas in case studies receive oral or parenteral anticoagulation therapy, one larger cohort showed that 15% of patients received no blood thinning regimen.[4][10] Underlying causes of spontaneous retroperitoneal hematoma include rupture of parenchymal lesions such as angiomyolipomas, cysts, and renal carcinomas or underlying vascular malformations such as aneurysm or pseudoaneurysm of any number of retroperitoneal vessels. Vessels documented in case reports include the superior gluteal artery, various lumbar arteries, renal arteries, and pancreaticoduodenal arteries.[11]

Epidemiology

Traumatic Retroperitoneal Hematoma

The overall incidence of retroperitoneal hematoma is difficult to ascertain as the label comprises such a heterogeneous group of injuries. Traumatic retroperitoneal hematomas result from 67% to 80% of blunt injuries versus 20% to 33% of penetrating trauma. One retrospective series identified retroperitoneal hematoma in 12% of a population of stable patients with documented abdominal trauma. Most of these patients had renal injuries, as determined by computed tomography imaging. Renal injuries are estimated to affect up to 10% of those with blunt abdominal trauma.

Vascular injuries are more frequently identified in patients with penetrating trauma than blunt force injuries. Extensive vascular injuries, including direct aortic injuries, are rarely due to blunt force trauma; instead, avulsion injuries to smaller aortic branches more commonly occur and can cause centromedial (ie, zone I) retroperitoneal hematomas.[12] Pelvic fractures comprise an estimated 2% to 8% of all fractures. Severe fractures cause excessive bleeding, and extremely high mortality rates are frequently reported. Results from one prospective registry study showed the mortality rates of patients undergoing angioembolization for pelvic hemorrhage were 17.6% in comparison to a group that received no embolization with a mortality rate of 32.6%.[13] Blunt injuries to retroperitoneal organs are rare, with an incidence of 0.2% and 5%, respectively, but carry similarly high mortality rates of more than 20%.[2]

Nontraumatic Retroperitoneal Hematoma

The etiology of nontraumatic retroperitoneal hematoma can occur spontaneously or as percutaneous procedure complications. Retroperitoneal hematomas associated with cardiac catheterization have decreased in incidence over the years. While some of this decrease is related to the rise in radial artery access, even in patients where radial artery access was utilized, a small minority still had a retroperitoneal hematoma. A retrospective study from the early 1990s demonstrated an incidence of 0.5% for postcardiac catheterization retroperitoneal hematomas.[14] A similar study spanning 2007 to 2014 showed a decline in the incidence of retroperitoneal hematoma from 0.09% to 0.03% during the study period, demonstrating that this is an infrequent complication in the modern era. Patients with retroperitoneal hematoma, however, are at significantly higher risk for mortality, with an odds ratio of 3.59, and adverse cardiac events, with an odds ratio of 5.76.[6]

Spontaneous retroperitoneal hematoma is rare, with a reported incidence of approximately 0.6%, primarily from case reports, case series, and small retrospective cohorts.[15] An accurate incidence is difficult to ascertain as the condition is rare and heterogeneous in mechanism and presentation. One single-center retrospective study identified only 89 patients over 7 years. The observed mortality of that cohort was 5.6% during the first week and 19.1% at 6 months. Forty percent of that cohort required intensive care unit monitoring.[4] Results from a similar retrospective study that identified 100 patients with spontaneous retroperitoneal hematoma identified a 6% mortality rate directly attributed to retroperitoneal hematoma. The overall mortality rate of that cohort, however, was 20%, suggesting that retroperitoneal hematoma itself was more common in older adults.[10]

History and Physical

Accurate diagnosis requires a high clinical index of suspicion and a focused history and physical examination. The clinical features of retroperitoneal hematoma are primarily based on the injured organs. In patients with traumatic injuries, the diagnostic approach for retroperitoneal hematoma begins with the standard history and initial survey used in all trauma settings. Clinicians should obtain as much detail as possible regarding the exact mechanism of injury to determine the risk of specific injury patterns. In patients who are stable and able to provide a history, complaints of abdominal, flank, or back pain could be indicative of retroperitoneal hematoma. However, these complaints could also be consistent with intra-abdominal or musculoskeletal injuries. The clinician must maintain high clinical suspicion for retroperitoneal hematoma, as no reliable historical features help confirm the diagnosis. The physical examination should start with airway, breathing, and circulation evaluation following standard advanced trauma life support protocol. Immediate life-threatening conditions should be addressed as identified by primary and secondary surveys. Specific physical exam findings, such as an unstable pelvis, are suggestive of potential pelvic retroperitoneal hematoma, while penetrating trauma to the back or flank may be suggestive of renal or great vessel injury. Classic signs such as flank bruising are less useful in acute traumas.[3][16] Hemorrhage should be suspected as the primary cause of hypotensive shock in a patient with trauma. Clinicians may be guided by clinical history, mechanism of injury, and the physical exam findings when identifying occult bleeding sources. The clinician should consider retroperitoneal bleeding as a source of shock in those with trauma who do not have another clear source for blood loss.

Presenting signs and symptoms of spontaneous retroperitoneal hematomas are often vague and nonspecific. In several retrospective studies, abdominal pain seems to be the most common complaint in 46% to 67.5% of patients. Other complaints include pain in the back, flank, and hip. Nonspecific complaints were observed in other cases—symptoms of hypovolemia are also commonly observed. Reports of femoral nerve palsy present retroperitoneal hematoma symptoms.[17] A comprehensive physical exam should be conducted to evaluate all patients. Findings consistent with hypovolemia or anemia are common in patients with ongoing blood loss from a retroperitoneal hematoma. These can include tachycardia, hypotension, and poor peripheral perfusion. Abdominal tenderness may or may not be present. Findings such as flank ecchymosis are of poor sensitivity, present in only 6.5% of cases in one cohort and 1% in another.[4][10] Findings in patients who suffer retroperitoneal hematoma after undergoing percutaneous coronary intervention are similar to the above, including abdominal, flank, and back pain. Results from one study revealed that inguinal tenderness and swelling following the femoral approach presented in most retroperitoneal hematoma cases. Another common finding reported is femoral neuropathy, likely caused by nerve compression due to hematoma formation.[6][8]

Evaluation

Imaging Studies

The hallmark clinical feature of traumatic and nontraumatic retroperitoneal hematomas is their occult nature, as the physical examination is typically nondiagnostic, and findings on plain film imaging or ultrasonography are equivocal. Therefore, contrast-enhanced computed tomography imaging is the diagnostic modality for retroperitoneal hematoma.[1] Patients with significant blunt and penetrating trauma will undergo extensive computed tomography scanning as part of their trauma evaluation, which commonly reveals evidence of retroperitoneal hematoma and a sensitivity of approximately 100%. The bedside-focused assessment with sonography in trauma exams is notoriously unreliable in detecting a retroperitoneal hematoma.[2][18] Evaluation of patients with no history of trauma is more difficult. Computed tomography scans characterize the hematoma, location, and size, which informs management. Intravenous contrast extravasation is an independent predictor of the need for interventional radiology or surgical intervention.[10][11]

Laboratory Studies

The remainder of the evaluation of patients with retroperitoneal hematoma should include comprehensive laboratory evaluation commensurate with the patient’s overall presentation, including complete blood count to assess for anemia, a comprehensive metabolic panel to check for renal or electrolyte abnormalities, liver function tests to evaluate for hepatic dysfunction, coagulation studies to assess for coagulopathies and bleeding risk, especially those receiving anticoagulation, and a type and screen for transfusion protocols. Pancreatic injury may elevate serum amylase levels in patients with trauma with blunt abdominal injuries. Additionally, in patients who are symptomatic with blunt trauma, the presence of hematuria on a urinalysis may indicate underlying kidney injury.[3]

Treatment / Management

The management of retroperitoneal hematoma, regardless of etiology, is multifaceted and requires an interprofessional approach. Specific therapeutic interventions must be individualized depending on each patient's etiology and overall clinical condition. Treatment modalities include supportive care with close observation for patients who are stable, angioembolization, or surgical exploration for those who are unstable. In all instances, adequate resuscitation with blood products for acute hemorrhage is recommended according to standard trauma protocol.

Traumatic Retroperitoneal Hematomas

As with all cases of abdominal trauma, any overt peritonitis, refractory hemodynamic instability, or apparent free fluid in the abdomen necessitates laparotomy. Retroperitoneal injuries are often not isolated and commonly occur in conjunction with intra-abdominal injuries. Patients should be assessed and cases should be managed based on the totality of the injury burden. For patients presenting with penetrating abdominal trauma, retroperitoneal hematoma develops as a result of direct injury to solid organs, viscera, or vasculature. In most cases, surgical exploration is recommended to achieve hemostasis. For patients presenting with blunt abdominal trauma, the decision to proceed with surgical exploration depends on the clinical stability of the patient and the ability to identify the underlying etiology. Persistent hemodynamic instability and an expanding or pulsatile hematoma are indications of moving forward with surgical management.[3]

The specific location of retroperitoneal hematoma in blunt injury can be localized on contrast-enhanced computed tomography scans and utilized to guide management. Centromedial hematomas are commonly explored as the underlying etiology is often attributable to injury to the great vessels or one of their branches. Lateral injuries primarily comprise renal injuries that are amenable to conservative management in those who are stable with mild to moderate computed tomography findings; however, large hematomas that are expanding or show evidence of contrast extravasation may require surgical exploration or angiographic embolization.[19] Pelvic retroperitoneal hematomas are primarily the result of pelvic fractures and venous bleeding. These injuries are less amenable to surgical management. The initial approach to the patient with presumed blood loss due to pelvic injury is an external pelvic fixation or binding to slow or tamponade the bleeding. Definitive management is by angiographic embolization of the bleeding vessels.[13](B2)

Nontraumatic Retroperitoneal Hematomas

The treatment of nontraumatic retroperitoneal hematoma is mainly based on the location and bleeding characteristics. Anticoagulation is common in patient populations who develop a spontaneous retroperitoneal hematoma, and reversal of the coagulopathy is recommended to prevent further bleeding. Additionally, appropriate resuscitation should be provided for patients demonstrating hemodynamic instability. Blood transfusion should be ordered for patients with signs and symptoms or lab findings of anemia. Specific therapeutic modalities will depend upon the location and extent of bleeding and whether or not evidence of contrast extravasation is apparent on contrast-enhanced computed tomography scans. Results from several retrospective cohort studies have shown that most patients with spontaneous retroperitoneal hematoma and patients with postprocedural retroperitoneal hematoma do well with supportive care and blood transfusion alone. In one series, 24.7% of patients underwent an embolization procedure, and 6.7% underwent a surgical procedure. Seventy-five percent of the cohort received a blood transfusion.[4] In another series of 100 patients with retroperitoneal hematoma, the rate of invasive management (eg, interventional radiology procedures or surgery) was only 16%. One of the most significant predictors of the need for invasive therapy was contrast extravasation in computed tomography imaging.[10](B2)

Differential Diagnosis

Differential diagnoses should include:

Traumatic 

• Acute abdomen
• Perforated viscus
• Solid organ injury
• Vascular injury
• Pelvic fracture
• Abdominal compartment syndrome [20]

Nontraumatic

• Gastrointestinal bleeding
• Musculoskeletal pain
• Appendicitis
• Cholecystitis
• Diverticulitis
• Abdominal aortic aneurysm
• Pancreatitis
• Pyelonephritis [4][10][21]

Prognosis

The prognosis of retroperitoneal hematomas depends upon the extent and type of injury sustained. Aortic injuries carry significantly higher morbidity and mortality than isolated kidney injuries, causing a retroperitoneal hematoma. In one cohort of primarily blunt trauma-related retroperitoneal hematoma, mortality was 6.5% in the overall sample, with approximately 77% undergoing surgical management.[19] In a cohort dominated by penetrating trauma victims, mortality was noted to be 18%.[16]

The prognosis of spontaneous retroperitoneal hematoma is poor. This may reflect the fact that older patients with multiple comorbidities make up the majority of patients diagnosed with spontaneous retroperitoneal hematoma. One retrospective study found a mortality of 10% at 30 days, with 40% of patients requiring intensive care. This suggests that nearly half of spontaneous retroperitoneal hematomas are critical.[4]

Complications

Complications of retroperitoneal hematoma include:

• Infection or sepsis
• Symptomatic anemia
• Exsanguination with associated myocardial infarction, acute kidney injury, acute liver injury, diffuse cerebral hypoperfusion
• Abdominal compartment syndrome
• Small bowel or urinary obstruction [22][23]

Complications of surgical intervention include infection, damage to adjacent structures of the operative field, and worsening of bleeding. Complications of angioembolization include infection, damage to the vasculature, worsening of bleeding, contrast-induced nephropathy, and ischemia of embolized arterial distributions.