Angioembolization: pros and cons
The higher rate of nonoperative failure for injured spleens with vascular abnormalities has prompted an aggressive pursuit for the early diagnosis and treatment of vascular abnormalities. One of the earliest reports examining the role of angioembolization in patients with splenic injuries was a case series from Kings County Hospital Center in New York City.37 Using a variety of materials to embolize the splenic vessels, the authors were able to curtail splenic bleeding and, based on these successes, they began to collect data on subsequent patients with injured spleens. Several years later, the authors published the results of 60 patients undergoing angioembolization for blunt splenic injury with a 93% success rate for hemorrhage control and improved splenic salvage rates.33
Angioembolization is both a diagnostic and therapeutic intervention as it is effective in verifying the presence of a vascular abnormality and selectively embolizing its associated vessel to improve splenic salvage. In general, angioembolization is indicated for the termination of bleeding from intraparenchymal or extraparenchymal splenic blushes. When the presence of an actively bleeding vessel or ‘blush’ is noted on the initial CT scan, it is associated with more than a 20-fold increased risk of splenectomy.2
Although angioembolization is indicated for defined vascular abnormalities present on the initial CT scan, it may also be considered for higher-grade splenic injuries even when there is no obvious vascular abnormality identified.2 30 34 35 38 39 Differences in the timing of the arterial contrast bolus may influence the visibility of these abnormalities on the CT scan. Some surgeons recommend that patients who sustain higher-grade splenic injuries should undergo angiography after the initial CT scan to identify any latent vascular abnormalities.5 36 39 Although lower-grade splenic injuries may contain several vascular abnormalities, Haan et al showed that the use of routine angioembolization to detect latent vascular abnormalities in these patients resulted in a low yield and hence were unnecessary procedures.40 Studies like these have helped to focus the routine use of angiography for those patients with high-grade splenic injuries as failure rates for nonoperative management decreased.38 39
Despite the evidence to support angiography for high-grade splenic injuries, the adaptation of such protocols to do so remains controversial. A survey of 260 members of the AAST showed that only 25% thought that grades IV and V splenic injuries should undergo mandatory angiography.41 The hesitancy to adopt strict angiography protocols may be based on studies that have shown no consistent improvement in patient outcomes after angiography was performed, even for high-grade splenic injuries.4 35 39 40 42 Further, angioembolization has some drawbacks including (1) despite selective or main artery splenic angioembolization, the spleen can bleed, indicating that the procedure does not ensure splenic salvage (figures 1–3); (2) angiography may not identify a vascular abnormality that was seen on CT scan, hence making selective angioembolization challenging; and (3) despite selective angioembolization of a segmental artery, vascular abnormalities not related to that segmental artery may arise and splenic bleeding may occur at a later time42 43 (figures 4 and 5). Haan and colleagues studied 126 patients who sustained blunt splenic injury and underwent angiography to enhance the rate of splenic salvage.3 Although 86 (68%) patients had normal angiographic findings, that is, no identifiable blush to embolize, seven of the patients subsequently bled and required splenectomy. The other 40 (32%) patients underwent angioembolization for positive angiographic findings (actively bleeding vessels) but three of those patients bled and required splenectomy. Both groups had statistically similar splenic salvage rates as 10% in either group failed to achieve hemostasis. Another study examined the efficacy of angiography for blunt splenic trauma and found that of the 349 patients who were managed nonoperatively, 46 had angioembolization whereas the remaining 303 underwent observation only.4 The authors found that both groups were well matched for age, gender, initial and lowest systolic blood pressure, and hospital length of stay. When the outcomes of the 46 patients were compared with those patients who underwent observation alone, there were no statistically significant differences, thus diminishing enthusiasm for the routine use of angiography for blunt splenic injuries. Further, there are data to suggest that angiography may not be as effective in preserving spleens after blunt splenic injury as some studies using retrospective controls indicate. Harbrecht et al showed that there has been a significant increase in the detection of minor spleen injuries over time as the resolution of the CT scanner has improved.4 A higher detection rate of minor injuries would enrich the denominator with patients who are unlikely to bleed, making nonoperative management appear more successful than overall studies indicate. Compared with historical controls with patients who sustained fewer lower grade injuries in the denominator, a spurious reduction in splenectomy rates may appear to be attributed to the use of angioembolization when, in fact, it is more likely due to more patients with lower grade splenic injuries in the denominator. In a multi-institutional study, the six-month risk of delayed splenectomy after nonoperative management showed no positive association between angiography and splenic salvage.44 Without a randomized controlled trial to guide management, there is likely to be continued controversy in this area of blunt splenic injury management. Regardless of the success or failure of angioembolization in controlling bleeding, the procedure has some drawbacks as previously noted and potential complications, such as rebleeding, splenic abscess, and iatrogenic vascular injury to another organ or vessel, and adverse immune function. Bessoud et al evaluated the immunological effects after proximal splenic artery angioembolization in 37 patients by examining for Howell-Jolly bodies (basophilic nuclear remnants found in the blood after splenectomy) and serum antibody titers for pneumococcus and Haemophilus influenza B.45 The Howell-Jolly bodies were found in only 2 patients and yet all 37 patients had sufficient immunity as measured by a response to the H influenza B. Based on these findings, the authors concluded that immune function remains relatively normal after proximal splenic artery embolization. The authors recognized that this study has a small number of patients and no control group, so they suggested that a large prospective study would add more credibility to the findings. In a systematic review and meta-analysis, authors from the University of Southern California found that proximal and selective angioembolization had equivalent rates of rebleeding, infarctions, and infections, hence underscoring that proximal splenic artery embolization is not necessarily harmful compared with a selective procedure.42 Overall, despite some drawbacks, angioembolization is a valuable tool in the nonoperative management of patients with blunt splenic injury but its timing relative to the injury may be crucial. In a study that compared the results from high-use ANGIO centers (those with ANGIO use proportion >20%) and low-use ANGIO centers (those with ANGIO use proportion >0.01% to 19.9%), the authors found that the high-use centers performed the angiography sooner and therefore are more often associated with splenic salvage.39 Similarly, Banerjee noted that centers that used frequent angioembolization of the splenic artery had higher rates of splenic salvage.35
Figure 1Pseudoaneurysm (arrow) noted on initial CT scan.
Figure 2Selective angioembolization of bleeding splenic vessel (arrow).
Figure 3Specimen shows embolized portion of spleen as dark area (arrow). Bleeding occurred from splenic hilum.
Figure 4Transverse image of spleen with pseudoaneurysms in the upper pole. Contrast is poorly timed as neither the aorta nor pseudoaneurysm appear bright.
Figure 5Repeat CT scan showing splenic hematoma and extraparenchymal pseudoaneurysm (arrow).