The spleen, an important component of the reticuloendothelial system in normal adults, is a highly vascular solid organ that arises as a mass of differentiated mesenchymal tissue during early embryonic development. The normal adult spleen weighs between 75 and 100 g and receives an average blood flow of 300 mL/min. It functions as the primary filter of the reticuloendothelial system by sequestering and removing antigens, bacteria, and senescent or damaged cellular elements from the circulation. In addition, the spleen has an important role in humoral immunity because it produces immunoglobulin M and opsonins for the complement activation system.
The increased availability of high-resolution CT scan and advances in arterial angiography and embolization techniques have contributed to the success of nonoperative management of splenic injuries.
The hemodynamically stable patient with blunt splenic trauma can be adequately managed with bed rest, serial abdominal exams, and hemoglobin and hematocrit monitoring. This approach, in combination with occasional angiography, especially for grade III and IV injuries, confers a splenic salvage rate of up to 95%.
In the setting of expectant management, indications for angiography have been delineated by several studies and include the following CT scan features: contrast extravasation, the presence of a pseudoaneurysm, significant hemoperitoneum, high-grade injury, and evidence of a vascular injury. The goal of angiography is to localize bleeding and embolize the source with coils or a gelatin foam product. Embolization can occur either at the main splenic artery just distal to the dorsal pancreatic portion of the vessel—known as proximal embolization—or selectively at the distal branch of the injured vessel. The goal behind the former technique is to decrease the perfusion pressure to the spleen to encourage hemostasis. The disadvantage to this technique is global splenic ischemia, and many have questioned the spleen’s immunocompetence following proximal embolization.
Malhotra et al. examined the effects of angioembolization on splenic function by examining serum levels of a particular T-cell line. T-cell proportions between patients who had undergone splenic embolization with asplenic patients and healthy controls were similar suggesting some degree of splenic immunocompetency was maintained. A Norwegian study comparing blood samples from patients who had undergone angioembolization with healthy controls demonstrated that the study samples had similar levels of pneumococcal immunoglobulins and no Howell-Jolly bodies, suggesting normal splenic function. Although these preliminary studies remain encouraging, there is no definitive evidence that splenic immunocompetency is fully maintained following angio-embolization.
There is no question that advancements in interventional techniques have contributed to the successful nonoperative management of splenic injuries. This has certainly changed the strategy, but it has not completely replaced operative intervention. The challenge now remains predicting those patients who will ultimately require splenectomy.
Many groups have studied potential predictors of nonoperative failure. Earlier studies found that a higher injury grade, increased transfusion requirement, and hypotension on initial presentation consistently predicted failure of nonoperative management. More recent literature reflects the use of advanced imaging techniques for predicting which patients will ultimately require splenectomy. Haan looked at the overall outcomes of patients admitted with blunt splenic trauma and reported several radiographic findings that were prevalent among patients requiring splenectomy after angioembolization:
- contrast extravasation,
- significant hemoperitoneum,
- and arteriovenous fistula.
Among these characteristics, an arteriovenous fistula had the highest rate of nonoperative failure at 40%. Nonradiographic features associated with significant risk of nonoperative failure include age greater than 40, injury severity score of 25 or greater, or presence of large-volume hemoperitoneum.
Aside from radiographic findings, some groups have also examined the mechanism of injury and its association with nonoperative failure. Plurad et al. conducted a retrospective review over a 15-year period and found that patients who were victims of blunt assault were more likely to fail nonoperative management: 36% of these patients required splenectomy versus 11.5% of patients from all other mechanisms combined. These findings suggest that regardless of overall injury severity, individuals who sustain a direct transfer of injury to the left torso are more likely to require splenectomy.
Currently, the accepted standard of care for most splenic trauma is expectant management with close observation. Operative intervention is reserved for the hemodynamically labile patient who shows signs of active hemorrhage and who does not respond appropriately to fluid resuscitation. Although these clinical scenarios seem straightforward, it is often the condition of the patient who falls in between the two ends of the spectrum that can be the most challenging to manage. In the setting of advanced imaging techniques and interventional radiology, the trauma surgeon has more diagnostic information and more treatment options for the patient with splenic trauma.