Traumatic Retroperitoneal Hematoma – Causes, Symptoms

The retroperitoneal space lies directly posterior to the peritoneal cavity. An organizational schema dividing the retroperitoneal space into three different “zones” is widely prevalent in the surgical literature.

• The central-medial zone (Zone I) falls between the two psoas muscles and contains midline structures such as the abdominal aorta, inferior vena cava, pancreas, and duodenum.
• The perirenal zone (Zone II) begins lateral to the psoas muscles on either side and contains the kidneys, ureters, and portions of the colon.
• The pelvic zone (Zone III) includes the bladder as well as a multitude of vascular structures, including a robust network for presacral veins. Also, the retroperitoneum contains vital musculoskeletal structures such as the psoas muscles, vertebra, quadratus lumborum, and iliacus muscles. It houses connections to the diaphragm and bony pelvis.[rx]

The term “retroperitoneal hematoma” comprises several distinct clinical entities that are best characterized according to their underlying mechanisms. The easiest way to dichotomize this diagnosis is to classify retroperitoneal hematoma as traumatic versus nontraumatic. The traumatic retroperitoneal hematoma heading can be further subdivided into penetrating versus blunt. The nontraumatic retroperitoneal hematoma category can be further broken down into spontaneous and iatrogenic.[rx][rx][rx]

Types of Retroperitoneal Hematoma

Traumatic Retroperitoneal Hematoma

• The true overall incidence of retroperitoneal hematoma is difficult to ascertain as the label comprises such a heterogeneous group of injuries. Traumatic retroperitoneal hematomas are more commonly the result of blunt injuries (67-80%) versus penetrating (20 to 33%). One retrospective series identified retroperitoneal hematoma in 12% of a population of stable patients with documented abdominal trauma. The majority of these patients suffered from renal injuries as identified on computed tomography (CT) scan. It is estimated that renal injury affects up to 10% of those suffering blunt abdominal trauma.[rx]
• Large vascular injuries such as direct aortic injuries due to blunt trauma are rare. However, avulsion injuries to smaller aortic branches often occur and can be a cause of centromedial (Zone I) retroperitoneal hematoma.
• Pelvic fractures comprise an estimated 2 to 8% of all fractures. Severe fractures often cause excessive bleeding, and extremely high mortality rates are often reported. In one prospective registry study, the mortality rates of those undergoing angioembolization for pelvic hemorrhage were 17.6%. This is in comparison to the group that received no embolization with a mortality rate of 32.6%.[rx]
• Blunt injuries to other retroperitoneal structures such as the duodenum and pancreas are rare in incidence (0.2% and 5%, respectively) but carry similarly high mortality rates, each cited above 20%.[rx]

Non-traumatic Retroperitoneal Hematoma

The etiology of non-traumatic retroperitoneal hematoma can be related to complications of percutaneous procedures or spontaneous in nature.

• Retroperitoneal hematoma related to cardiac catheterization has been decreasing in incidence over the years. While some of this decrease can be related to the rise in radial artery access, it is interesting to note that even in cohorts of radial artery access, a small minority of patients still suffered a retroperitoneal hematoma. A retrospective study from the early 1990s demonstrated an incidence of 0.5% for post-cardiac catheterization retroperitoneal hematomas.[rx] A similar study spanning 2007-2014 showed a decline in incidence in retroperitoneal hematoma from 0.09% to 0.03% during the study period, demonstrating that in the modern era, this is an infrequent complication. Patients who do suffer retroperitoneal hematoma, however, are at significantly higher risk for mortality (odds ratio 3.59) and adverse cardiac events (odds ratio 5.76).[rx]
• Spontaneous retroperitoneal hematoma is a rare occurrence confined mainly to case reports, case series, and small retrospective cohorts. Clearly defined incidence is difficult to ascertain as the disease entity is rare and heterogenous in mechanism and presentation. One single-center retrospective study identified only 89 patients over a seven-year period. The observed mortality of that cohort was 5.6% during the first week and 19.1% at six months. Forty percent of that cohort required ICU monitoring.[rx] A similar retrospective study that identified 100 spontaneous retroperitoneal hematoma patients 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 an elderly, moribund population.[rx]

Causes of Traumatic Retroperitoneal Hematoma

Retroperitoneal hematomas are the result of blood loss due to the injury of parenchymal tissue or vascular structures within the retroperitoneal cavity.

Traumatic Retroperitoneal Hematoma

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 victim. The blunt mechanism results in compressive and deceleration forces, which often lead to 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 trajectory of the knife or missile. It is important to note that many of these penetrating injuries will have concomitant injuries within the peritoneal cavity as well.[rx]

Non-traumatic Retroperitoneal Hematoma

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 (PCI) or endovascular procedures. While the literature demonstrates that this is a rare complication of such procedures, associated morbidity and mortality are high when it does occur. Rates of PCI 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.[rx]
• Risk factors for retroperitoneal hematoma following PCI appear to be arterial puncture above the level of the inguinal ligament, female sex, treatment with GPIIb/IIIa inhibitors, and treatment with warfarin.[rx][rx][rx]
• Spontaneous retroperitoneal hematoma is a relatively rare clinical entity 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 the elderly, patients receiving anticoagulation therapy, and those with underlying coagulopathy. While a majority of patients who suffer retroperitoneal hematomas are receiving anticoagulation therapy (oral or parenteral), it is important to note that in one larger cohort, showed that 15% of patients were receiving no blood thinning regimen.[rx][rx]

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 implicated in case reports have included a wide range, such as the superior gluteal artery, various lumbar arteries, renal artery, and pancreaticoduodenal artery.[rx]

Diagnosis of Traumatic Retroperitoneal Hematoma

History and Physical

The mainstay of diagnosis for retroperitoneal hematoma is a contrast-enhanced CT-scan. The hallmark feature of retroperitoneal hematomas, both traumatic and nontraumatic, is their occult nature. The physical examination is commonly nondiagnostic at best, and they are not readily detectable on plain film imaging or ultrasonography.[rx]

Patients who are victims of significant blunt and penetrating trauma will likely undergo extensive CT scanning as part of their trauma workup. These scans will commonly reveal evidence of retroperitoneal hematoma, with sensitivities reportedly approaching 100%. The bedside focused assessment with sonography in trauma (FAST) exam is notoriously unreliable at detective presence of a retroperitoneal hematoma.[rx][rx]

• CT scan – serves to identify presence, location, and to guide therapy of retroperitoneal hematoma potentially. The presence of intravenous contrast extravasation has been shown to be an independent predictor of the need for interventional radiology or surgical intervention.[rx][rx]
• Ultrasonography (USG) –  CT, and MRI  all are highly beneficial in the diagnosis of adrenal myelolipoma, with CT scan being the most sensitive for identification of fat within the lesions. As these tumors are nonfunctional, endocrinological tests are not useful as these lesions are mostly functionally inert. The differential diagnosis of fat-containing retroperitoneal masses would include retroperitoneal lipoma or liposarcoma and renal angiomyolipoma.
• USG – Myelolipoma has the typical appearance of a hyperechoic mass with intermixed hypoechoic regions. Echogenicity is mainly determined by the variable proportions of the constituent elements in the lesion. The areas of intermixed fatty and myeloid tissue are the most echogenic, whereas regions of pure fat may appear hypoechoic. Because of inhomogeneous architecture, myelolipomas often have heterogeneous echogenicity. Calcification foci appear hyperechoic with acoustic shadowing. Myelolipoma has vague and no appreciable margins due to having almost the same echogenicity as surrounding retroperitoneal fat. Hemorrhage alters the sonographic picture, with hemorrhagic areas appearing hypoechoic compared with fat.[rx][rx]
• CT – CT is the preferred imaging modality for the diagnosis of adrenal myelolipoma. It is seen as a hypodense well-circumscribed heterogeneous mass with an attenuation value of -90 to -129 HU. Almost all myelolipomas have some focus of fat, although the fatty tissue focus may be very small. Large amounts of fat are frequently encountered with “smoky” or “variegated” areas of interspersed higher-attenuation tissue. This denser tissue has attenuation values of 20 HU to 30 HU, inferring the presence of both fat and myeloid elements. Myelolipomas are usually relatively well circumscribed, however, due to the presence of abundant fat they can be difficult to distinguish from surrounding retroperitoneal fat. Foci of punctate calcification may be seen in 25% to 30% of cases. CT is the most sensitive for detecting hemorrhage which may be hyper to hypodense depending on the age of evolution.
• MRI – The predominantly fatty areas in myelolipoma appear hyperintense on T1 MR images and intermediate to hyperintense on T2. Admixed marrowlike elements have medium intensity signals similar to that of the spleen. Fat-suppression techniques are best for demonstrating the fat in a myelolipoma with MR imaging. The presence of marrow like elements or hemorrhage results in persistent areas of increased signal intensity on fat-suppressed MR images. Opposed-phase imaging demonstrates signal loss in admixed voxels containing both fat and myeloid tissue which is also described for adrenal adenoma and other masses with mixed components. At MR imaging, the signal intensity will vary depending on the presence and age of hemorrhage. Post-contrast images show a striking enhancement. The imaging features of extra-adrenal myelolipoma are similar to those of adrenal myelolipoma and do not allow distinction extra-adrenal myelolipoma from other fat-containing tumors.
• Positron emission tomography (PET) – Adrenal myelolipomas typically do not demonstrate an avid FDG uptake, which is usually less than that of the liver. However, in rare instances, the adenomatous and hematopoietic elements can show an increased FDG uptake.[rx]

Treatment of Traumatic Retroperitoneal Hematoma

The management of retroperitoneal hematoma, regardless of etiology, is multifaceted and requires an interprofessional team approach. Specific therapeutic interventions must be individualized, depending upon the etiology and overall clinical condition of each patient. Treatment modalities include supportive care with close observation for stable patients or angioembolization/surgical exploration for more unstable patients. In all instances, adequate resuscitation with blood products for acute hemorrhage should be undertaken in the usual fashion.

Traumatic Retroperitoneal Hematoma

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 managed based upon the totality of their 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 the majority of these 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, an expanding or pulsatile hematoma, are all indications to move forward with definitive surgical management.[rx]
• The specific location of retroperitoneal hematoma in the setting of blunt injury is often able to be localized on contrast-enhanced CT scan, and can be utilized to guide management. Centromedial (Zone I) hematomas are commonly explored as the underlying etiology is often attributable to injury to the great vessels or one of their branches. Lateral (Zone II) injuries are largely comprised of renal injuries that are amenable to conservative management in the stable patient with favorable CT findings, however large hematomas which are expanding or show evidence of contrast extravasation may require surgical exploration or angiographic embolization.[rx]
• Pelvic (Zone III) 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 external pelvic fixation/binding, which may help to slow or tamponade the bleeding. Definitive management is by angiographic embolization of the bleeding vessels.[rx]

Non-traumatic Retroperitoneal Hematoma

The treatment of non-traumatic retroperitoneal hematoma is mainly based upon the location and characteristics of the bleeding.

• As noted above, anticoagulation is common in the patient populations who suffer from spontaneous retroperitoneal hematoma, and reversal of the coagulopathy should be undertaken to prevent further bleeding. Additionally, appropriate resuscitation should be undertaken for patients demonstrating hemodynamic instability. Blood transfusion should be ordered for those 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 there is evidence of contrast extravasation on contrast-enhanced CT scan. Several retrospective cohort studies have shown that a majority of patients with spontaneous retroperitoneal hematoma and even those with post-procedural 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.[rx] In another series of 100 patients with retroperitoneal hematoma, the rate of invasive management (IR intervention or surgery) was only 16%. One of the greatest predictors of the need for invasive therapy was contrast extravasation on CT scan.[rx]

Differential Diagnosis

Traumatic Retroperitoneal Hematoma

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

Non-traumatic Retroperitoneal Hematoma

• GI bleeding
• Musculoskeletal pain
• Appendicitis
• Cholecystitis
• Diverticulitis
• Abdominal aortic aneurysm
• Pancreatitis
• Pyelonephritis

Prognosis

Traumatic Retroperitoneal Hematoma

Prognosis 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.[15] In a cohort dominated by penetrating trauma victims, mortality was noted to be 18%.[rx]

Non-traumatic Retroperitoneal Hematoma

Prognosis of spontaneous retroperitoneal hematoma is poor overall. This may reflect the fact that elderly 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. Forty percent of those studied required ICU care, suggesting that nearly half of the cases are critical.[rx]

Complications

Complications of retroperitoneal hematoma include:

• Infection/sepsis
• Symptomatic anemia
• Exsanguination
• Abdominal compartment syndrome