This study offers a new perspective in proximal splenic artery embolization, with the use of plug alone in comparison to combination embolization with additional coils. There is a significant decrease in adverse events with the use of vascular plug alone, that contributes to overall splenic preservation. The importance of the spleen in maintaining the body’s immune system and antibody production is well known, with knowledge that open splenectomy is strongly associated with systemic infection (Demetriades et al., 2012). Therefore, splenic preservation treatment options are important in the management of splenic trauma, with splenic artery embolization widely accepted as a safe and effective treatment in patients with hemodynamically stable grade III or higher splenic injury (Haan et al., 2005; Brahmbhatt et al., n.d.; Cretcher et al., 2021; Quencer & Smith, 2019). Technical success was achieved in all patients in this study with grade IV or higher splenic trauma, comparable to the rates described in the literature (Habash et al., 2021; Frandon et al., 2014; Cinquantini et al., 2018). Cessation of bleeding and maintained hemodynamic stability occurred in 94.7% of the patients, comparable to literature rates of both distal and proximal SAE (Habash et al., 2021; Frandon et al., 2014; Banerjee et al., 2013; Wu et al., 2008; Ekeh et al., 2013). The splenic salvage rate in this study was 96.1%, comparable to the reported literature rates in proximal SAE with the use of coil and plug embolization (Habash et al., 2021; Jambon et al., 2018; Quencer & Smith, 2019; Zhu et al., 2011).
Combined embolization, such as with plug and coil in proximal SAE, is described in the literature (Habash et al., 2021; Patil et al., 2020; Brahmbhatt et al., n.d.; Quencer & Smith, 2019; Zhu et al., 2011). However, there are no dedicated analyzes comparing the use of combined embolic agents to single embolic agents. Due to local practice, it was possible to compare the outcomes in proximal splenic artery embolization with the use of a plug versus plug and coils. Interestingly, this demonstrated a statistically significant increased adverse event rate in the group of patients that had embolization with both plug and coils (p = 0.036). The most common adverse event was splenic infarct. One postulation for the increased rate of splenic infarct may be due to the theoretical faster time to complete occlusion with the addition of coils. As a result, collateral vessels may not be established to perfuse the spleen in certain patient populations, resulting in ischemia, and ultimately infarct, of the spleen. Additionally, with addition of coils, the landing zone of the embolic agents is longer, which could result in the occlusion of the ostia of potential collateral vessels to the spleen. Other factors could be involved, but further studies would be required to establish this relationship. A potential benefit of proximal SAE with plugs alone could include a “plug and forget” approach where the operator would deploy the plug without having to chase it with a coil or wait for complete stasis of flow to terminate the intervention. This offers reassurance in the procedural outcomes, such that there should theoretically be a decrease in need for additional radiation with need for less repeat angiographic images and fluoroscopy time following deployment of the plug. Furthermore, the procedural time should also theoretically decrease in this approach as the need for further embolization was shown to not needed to achieve a desired outcome of hemodynamic stability in this study.
The literature reported adverse event rates up to 20–29% for major adverse events, which include splenic infarct, splenic abscess, and continued bleed necessitating open splenectomy (Habash et al., 2021; Wu et al., 2008; Ekeh et al., 2013). This is comparable to moderate to severe adverse events per the new SIR guidelines, and the rate of moderate to severe adverse events is lower with proximal SAE than distal SAE as described in several reviews (Brahmbhatt et al., n.d.; Frandon et al., 2014; Wong et al., 2017; Quencer & Smith, 2019; Cinquantini et al., 2018). The most common adverse event in this study was splenic infarct, occurring in seven of the patients (9.2%). Three patients required open splenectomy within 1–5 days following embolization, which was documented as severe adverse events, but are considered treatment failure rather than a complication of the procedure.
Following SAE, the development of a left-sided pleural effusion has been described, thought to be from irritation of the diaphragm from inflammation in upper pole splenic embolizations (Habash et al., 2021; Cinquantini et al., 2018; Araten et al., 2014; Wu et al., 2008; Ekeh et al., 2013). This is a known adverse event described in SAE for hypersplenism (Araten et al., 2014), and this was investigated in this study as a surrogate marker for degree of splenic inflammation that SAE caused. This occurred in eight of the patients in this study (10.5%), which is lower than Wu et al (Wu et al., 2008) (33%) that had distal embolization patients and Ekeh et al (Ekeh et al., 2013) (17%) that saw a similar number in both proximal, distal, and combined SAE. There was no statistically significant difference in the rate of left pleural effusion based on embolization techniques in this study. The overall percentage of this adverse event was similar in literature reports, with a higher rate reported in distal upper splenic embolizations (Araten et al., 2014; Wu et al., 2008; Ekeh et al., 2013). Interestingly, the adverse event rates in this study were similar to the literature despite the proximal embolization location being placed over the dorsal pancreatic artery origin. This suggests good alternative collaterals are available proximal to this vessel origin to maintain flow to the surrounding solid organs. The mortality rate between the two groups in this study was not significantly different and were due to polytrauma with other injuries that the patient ultimately succumbed to.
In the setting of proximal SAE, the procedure time and radiation dose has been described in literature to be decreased in comparison to distal SAE (Quencer & Smith, 2019; Johnson et al., 2021; Zhu et al., 2011). In comparison of plug to coil, Zhu et al. (Zhu et al., 2011) found that the procedure time was not significantly different, with a trend toward decrease in the plug alone group. However, the radiation dose was significantly decreased with the use of a plug compared to coil for proximal SAE (Zhu et al., 2011). Similar results have been reported with other reviews and studies (Jambon et al., 2018; Johnson et al., 2021). Due to a migration of the data storage system at the local institute during the study data review period, the details of procedure length were not available for review, and the total radiation dose was only available in 31 cases. This showed no statistically significant difference between the use of plug and combination embolization, which is likely due to the small sample size.
There are limitations to this study. First, as a retrospective cohort review, the nature of the study leads to possible cofounding factors that are not fully accounted for in the analysis such as patient past medical history, medication history or associated traumatic injuries. Additionally, this is a single centre review, which could limit the range of external validity. Furthermore, not all data points where available for the entirety of the study population. Moreover, as the use of the embolic agents is up to the interventionist at the time of the procedure and not standardized, there may be other procedural factors not documented that could ultimately skew the results if the sicker or more complex patients were heavily represented in one group over the other.
Follow-up imaging was limited in this study, with only 35 patients getting CT scans in the same institution after the embolization. This would limit the assessment of the cessation of bleeding or resolution of the pseudoaneurysm from an imaging perspective. If the patient was clinically stable, the local clinical practice, and to appropriately utilize resources, favor to not further image the patient. This would not significantly limit the assessment of clinical success in this study, as patients that did not require further imaging were clinically stable, although there remains a possibility of under-representing persistent small pseudoaneurysms.