Splenic artery embolization for trauma: a narrative review

Article information

J Trauma Inj. 2024;37(4):252-261

Publication date (electronic) : 2024 December 16

doi : https://doi.org/10.20408/jti.2024.0056

Simon Roh, MD

Department of Interventional Radiology, St. Luke’s University Hospital, Bethlehem, PA, USA

Correspondence to Simon Roh, MD Department of Interventional Radiology, St. Luke’s University Hospital, 801 Ostrum St, Bethlehem, PA 18015, USA Tel: +1-484-526-4716 Email: simon.roh@temple.edu

Received 2024 August 21; Revised 2024 September 26; Accepted 2024 October 21.

Abstract

INTRODUCTION

The spleen is one of the most frequently injured solid organs in cases of blunt trauma. Traditionally, splenic injuries have been treated with splenectomy. However, over recent decades, there has been a shift towards more conservative treatment methods. This change is due to the critical role the spleen plays in immune function; patients without a spleen are at increased risk of opportunistic infections, including overwhelming post-splenectomy infection syndrome [1,2]. Conservative management of splenic trauma typically involves nonoperative measures, such as angiography and embolization, especially for patients who continue to exhibit signs of blood loss [2]. This review article will discuss current trends in the management of splenic trauma, with a detailed examination of splenic artery embolization (SAE) techniques.

SPLENIC INJURY GRADING

In trauma cases, the spleen is often evaluated using imaging techniques, primarily computed tomography (CT) and ultrasound. The grading of splenic injuries typically utilizes two main systems: the American Association for the Surgery of Trauma (AAST) spleen organ injury scale (Table 1) [3] and the World Society of Emergency Surgery (WSES) spleen trauma classification (Table 2) [4]. The AAST organ injury grading scale includes CT findings of splenic injuries and integrates several criteria from the CT severity index (CTSI) [3,5].

Table 1.

AAST spleen organ injury scale 2018 revision

Table 2.

WSES spleen trauma classification

Multiphase CT with intravascular contrast, encompassing arterial, venous, and delayed phases, can aid in resolving abnormal findings. The arterial phase is useful for detecting vascular injuries, the portal venous phase helps characterize parenchymal defects, and the delayed phase assists in distinguishing between active arterial bleeding and contained vascular injuries, such as pseudoaneurysms or arteriovenous fistulas [6].

MANAGEMENT OF PATIENTS SUSTAINING SPLENIC TRAUMA

Patients who sustain trauma are assessed in the emergency department, where Focused Assessment with Sonography for Trauma (FAST) is a mainstay to evaluate hemoperitoneum [7]. Diagnostic peritoneal lavage may also be used to assess hemoperitoneum, though a positive result does not specifically identify the injured organ [7]. If a patient is found to be hemodynamically unstable with evidence of hemoperitoneum and splenic injury, an immediate laparotomy is required to control active bleeding [8]. Currently, splenorrhaphy is rarely performed in modern trauma centers, with only 1.4% of patients undergoing this procedure [9].

If a patient is hemodynamically stable, conservative management with CT imaging to assess for internal organ injuries and serial hemoglobin monitoring to detect ongoing hemorrhage is appropriate [10]. High-grade spleen injuries (AAST grades III–V) may warrant angiography, even in the absence of active bleeding on CT scans [11,12]. The management of CTSI grade III splenic injuries continues to be controversial. Nonoperative management (NOM) and a follow-up CT at 72 hours to monitor for injury progression are recommended, as patients with grade III injuries have demonstrated higher rates of NOM failure [5].

NOM for all grades of splenic injuries demonstrated a clinical success rate ranging from 100% for AAST grade I injuries to 83.3% for grade V injuries [13]. The success rate of NOM increased when SAE was selectively incorporated into the management plan for patients exhibiting signs of ongoing blood loss, as well as prophylactic SAE for those at high risk of NOM failure [14–16]. Patients at high risk for NOM failure include those with active contrast extravasation or pseudoaneurysm observed on CT, and those with high-grade splenic injuries (AAST grades III–V) [14]. The overall splenic salvage rate with NOM, which includes SAE as part of the management strategy, was 96.7% [17]. The decision to preemptively perform splenic artery angiography in patients with high-grade splenic injuries, even without CT evidence of vascular injury, remains a matter of debate [13,17,18]. The proposed management of splenic trauma patients is outlined in Fig. 1.

Fig. 1.

Proposed algorithm for the management of splenic trauma patients. AAST, American Association for the Surgery of Trauma; WSES, World Society of Emergency Surgery; NOM, nonoperative management; CT, computed tomography. ^a)Unsuccessful NOM includes the development of hemodynamic instability, hemoglobin levels showing a downward trend, diffuse peritonitis, and findings of vascular injury on imaging.

SPLENECTOMY VS. SPLENIC ARTERY EMBOLIZATION

NOM requires serial monitoring of a patient's hemodynamic status, hemoglobin levels, and repeat imaging as necessary [19]. A complete blood cell count is obtained every 6 hours, and arterial blood gas measurements are taken every 12 hours for a period of 48 to 72 hours to assess the success of NOM [13]. Unsuccessful NOM is characterized by hemodynamic instability, decreasing hemoglobin levels, the development of diffuse peritonitis, and evidence of vascular injury. At this stage, the patient may be considered for additional endovascular intervention if it has not already been performed, or for surgery [13]. Indications for SAE include active arterial contrast extravasation on CT, splenic vascular injuries such as pseudoaneurysm or arteriovenous fistula, high-grade injuries (AAST grades III–V), and hemoperitoneum [20]. Splenic artery angiography with embolization has been reported in 8.1% of patients undergoing NOM [11]. Delayed splenic rupture is a rare occurrence and may indicate either a delayed diagnosis or a missed splenic injury, which can also be successfully managed with NOM in a select group of patients [21].

The overall rates of NOM failure range from 3.4% to 27%, with increasing failure rates for higher grade injuries [17,22,23]. The NOM failure rate decreased from 13.3% to 3.1% when embolization was performed for pseudoaneurysms [24]. Untreated pseudoaneurysms can lead to high mortality rates [25]. Selective implementation of SAE among patients undergoing nonoperative treatment increases the success rate of NOM [26–28]. The failure rate of SAE that requires operative management ranges from 2.7% to 27% [14,16,22].

Splenectomy was not identified as an independent risk factor for mortality in one study [29]. Additionally, splenectomy was associated with lower morbidity rates compared to SAE [30]. However, other studies reported a lower mortality rate, along with shorter hospital stays and reduced costs, in patients who underwent embolization rather than surgery [22,31].

Hospital length of stay increases with the severity of splenic injury. The mean hospital length of stay varied from 11 to 13 days for patients undergoing splenectomy, from 9 to 11.94 days for those undergoing SAE, and from 6 to 7.56 days for those undergoing NOM without intervention across all grades of splenic injury [22,29,32]. The mean length of stay in the intensive care unit ranged from 7 to 8.62 days for patients undergoing splenectomy, from 4 to 8.14 days for those undergoing SAE, and from 3 to 5.55 days for those undergoing NOM without intervention [22,29,32]. Readmission for rebleeding following NOM occurs in 1.4% of patients within 180 days of discharge [33]. When comparing the mean costs of hospitalization for grade III to V injuries, the cost for NOM ranged from US $26,788 to $39,837, while the cost for SAE ranged from US $41,217 to $48,883 [34]. Although SAE is a relatively low-cost procedure [31], NOM without SAE may be a more cost-effective strategy in managing patients with high-grade splenic injuries. This is because the slightly improved outcomes among patients undergoing SAE may not justify the higher costs [34].

One of the main advantages of SAE compared to splenectomy is its capacity to preserve partial to nearly full splenic function. Maintaining splenic function helps preserve the patient's immunocompetence and prevents opportunistic infections. However, it remains uncertain what percentage of the spleen needs to remain post-embolization for a patient to be considered as having adequate immunologic function. Some institutions use 50% as the threshold to differentiate between sufficient splenic function and being functionally asplenic [35].

Patients who undergo splenectomy are at risk of infections from Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria meningitidis, necessitating lifelong immunizations against these pathogens. This requirement can be burdensome and confusing, leading to many patients not completing their vaccination protocols [35]. Splenectomy has been associated with a higher incidence of early infectious complications, such as pneumonia, compared to SAE in patients with AAST grade IV and V splenic injuries [29]. A systematic review further supports this finding, indicating an increase in infectious complications and a rise in immunosuppressive cells, alongside a decrease in immune-activating cells in patients who have undergone a splenectomy [36].

Patients who have undergone a splenectomy exhibit an increased susceptibility to certain cancers, including those of the head and neck, digestive tract, and hematologic malignancies [37]. The mechanism underlying the development of malignancy following splenectomy remains unclear; however, it is hypothesized that asplenic patients are immunocompromised and, consequently, at a higher risk for infections such as Helicobacter pylori, which is associated with gastric cancer [37].

Splenic artery embolization

Access

Endovascular therapy can be performed using either radial artery or femoral artery access [33]. Traditionally, the femoral artery has been the preferred access point. However, recent advancements have increased the use of radial artery access, particularly in mesenteric artery cannulation, even in trauma settings. A study comparing radial versus femoral access for SAE in trauma patients found that radial access led to quicker splenic artery cannulation and required fewer catheters for the procedure. There were no significant differences in procedure length, fluoroscopy time, radiation dose, or contrast volume [38]. The improvements in cannulation time and catheter usage with radial access may be attributed to the more favorable angle of the celiac artery relative to the aorta. However, the experience of the interventionist also plays a crucial role, as radial access may not be as familiar as femoral access to those with extensive experience in the latter. Ultimately, the choice of access should be determined by the interventionist, based on which method is safest and most efficient for treating the patient.

Embolization techniques

SAE is generally classified into two types: proximal and distal embolization [33]. Proximal SAE involves placing embolics between the origins of the dorsal pancreatic and great pancreatic arteries. Conversely, distal SAE refers to embolization performed beyond the origin of the caudal pancreatic artery (Fig. 2). A combination of the two can also be performed [39,40]. The choice of embolization technique depends on the severity of the splenic injury and the degree of selectivity required in the embolization process [11,41].

Fig. 2.

Diagram of splenic artery branches. Proximal splenic artery embolization is embolization performed between the origins of the dorsal and great pancreatic arteries. Distal splenic artery embolization is embolization performed distal to the origin of the caudal pancreatic artery.

Proximal embolization is performed for high-grade splenic injuries to reduce perfusion pressure to the spleen and help prevent ongoing hemorrhage [42]. The celiac artery is selectively cannulated using a reverse curve catheter, such as Simmons (Merit) and SOS (Angiodynamics), or a curved catheter, such as Cobra (Angiodynamics) or Rosch Celiac RC2 (Boston Scientific), depending on the acuity of the celiac artery's take-off angle [26,41,43,44]. Once the base catheter has been secured in the celiac artery, a celiac angiography is conducted to evaluate the collateral vascular supply to the spleen [20,40]. Efforts should be made to perform embolization between the take-off of the dorsal pancreatic and great pancreatic arteries to minimize the risk of pancreatic ischemia and to allow distal collateral flow into the spleen [40,44,45].

A microcatheter, ranging in size from 2F to 2.8F, is advanced through the base catheter into the proximal splenic artery [45]. Coil embolization is typically performed in the proximal splenic artery by oversizing the coils by 20% relative to the vessel diameter. This oversizing is crucial to prevent coil migration within the high-flow splenic artery. If the coils cannot be anchored in the proximal splenic artery, they may migrate distally, necessitating the use of a vascular plug [5].

Vascular plugs can be delivered through a microcatheter, but the maximum diameter suitable for a microvascular plug (MVP) is 5 mm. For vessel diameters greater than 5 mm, a larger 4F or 5F diagnostic catheter is required. If an Amplatzer Vascular Plug (AVP; Abbott) is necessary, advancing a 4F or 5F catheter into the proximal splenic artery is essential. However, advancing a diagnostic catheter into the splenic artery can be challenging due to several anatomical factors: the take-off angle of the splenic artery from the celiac artery, the acute angle of the celiac artery's take-off from the aorta, and calcifications or stenoses at the origins of the celiac and splenic arteries, which can significantly reduce luminal size and hinder the advancement of larger catheters. An advantage of using plugs is the reduction in fluoroscopy time, which decreases radiation exposure [46].

Distal SAE is typically performed when localized active hemorrhage or vascular anomalies are visualized, or when pseudoaneurysms are present [13,42,43]. This procedure is not necessarily linked to any specific grade of splenic injury. Access to the splenic artery is achieved using a microcatheter, as previously described. Digital subtraction angiography increases the likelihood of detecting small vessel hemorrhages [44]. To access third- or fourth-order branches of the splenic artery, various wires may be required. Wires as thin as 0.014 inch (0.04 cm) are usually available in the interventional suite. If thinner wires are necessary, utilizing equipment from cardiac or neurointerventional suites may be beneficial. Microcatheters with angled tips can be advantageous for accessing vessels that branch at sharp angles.

Embolic agents

The embolic agents most commonly used in SAE include coils, plugs, and gelatin sponges [33,42,44]. As noted in the previous section, plugs are primarily employed for proximal splenic embolization. MVPs are suitable for vessels ranging from 1.5 to 9 mm in diameter. MVPs that are compatible with a microcatheter can be utilized in vessels up to 5 mm. For vessels measuring between 5 and 7 mm, 4F catheters are necessary, while vessels between 7 and 9 mm require 5F catheters [47].

AVPs represent another type of device utilized in the interventional suite. AVPs come in three different configurations: AVP, AVP II, and AVP 4. The AVP 4 is the most commonly used model for SAE, as it is specifically designed for use in tortuous vessels [47]. Its deployment requires a diagnostic catheter capable of accommodating a 0.038-inch wire (0.1-cm wire), which typically corresponds to either a 4F or 5F diagnostic catheter, depending on the manufacturer. The AVP 4 is suitable for vessels ranging from 2.5 to 6 mm in diameter [45].

Coils are commonly utilized in SAE for their flexibility, ease of use, and broad availability from various manufacturers [43]. They can be classified into two main types: pushable and detachable. Pushable coils are less expensive and can be deployed more quickly, but they offer less precision in placement. Detachable coils, on the other hand, are ideal for use in vessels that demand precise coil positioning, as they can be retracted and redeployed until they are correctly positioned.

Many manufacturers are now offering coils that incorporate various agents, such as nylon fiber or hydrogel, attached to the main platinum coil element. These additions aim to enhance thrombus formation on the coils, thereby accelerating the embolization of the targeted vessel. Specialized hybrid coils, featuring rigid preformed loops followed by a long soft coil, have been demonstrated to reduce procedural and fluoroscopy times by facilitating faster embolization of the targeted vessel [48].

A gelatin sponge is a water-insoluble material composed of purified porcine skin, gelatin granules, and water. It is used as a temporary embolic agent and is typically absorbed completely within 4 to 6 weeks. The exact mechanism of action of a gelatin sponge is not fully understood, but it is thought to function through mechanical occlusion of the vessel, as it can absorb many times its weight in blood and fluids. Other materials such as polyvinyl alcohol particles, ethiodized oil, polymethylmethacrylate with Polyzene-F shell particles, and N-butyl cyanoacrylate have also been utilized in SAE [26,40,41,49].

HYBRID ANGIOGRAPHY SUITE IN THE EMERGENCY/OPERATING ROOM

Timely treatment of trauma patients is crucial. To accelerate the care process, several top academic medical centers have started integrating interventional fluoroscopy units into the emergency/operating room. The objective is to facilitate swift endovascular management of internal hemorrhages in trauma patients. Research has shown that the presence of an interventional suite within the emergency/operating room significantly speeds up patient treatment and improves outcomes [50].

COMPLICATIONS/PHYSIOLOGICAL CHANGES AFTER SAE

SAE has demonstrated a success rate exceeding 90% in controlling splenic hemorrhage in trauma settings [1,15,38,42,43,45,51,52]. Complication rates between proximal and distal splenic embolization have shown conflicting results, with some studies indicating higher rates for distal embolization, while others report similar rates for both techniques [11,27,39,42]. A meta-analysis showed lower rates of life-threatening complications (rebleeding, infarction, abscess, and contrast nephropathy) with proximal embolization (10.7%) than with distal embolization (30.7%) [53]. The lower complication rate associated with proximal embolization is attributed to the technically less challenging nature of the procedure, which results in faster procedure times and reduced contrast use. Additionally, the maintenance of flow to the splenic parenchyma through collateral vessels decreases the risk of splenic infarct [53]. Success rates in controlling hemorrhage using the two techniques have varied. One study reported a rebleeding rate of 11.8% for proximal embolization and 17.4% for distal embolization, with the latter requiring further management with splenectomy [54]. However, other studies have shown similar technical success rates between the two techniques in controlling hemorrhage [19,55]. Due to the decreased selectivity of proximal embolization, intraprocedural fluoroscopy times are shorter [54]. Additionally, combining proximal and distal embolization has been shown to result in lower rebleeding rates compared to using distal embolization alone [56].

The categorization of complications into major or minor categories depends on the definitions provided by the author. Despite this variability, the rate of major complications has been reported to range from 4% to 14%, including conditions such as splenic infarct, abscess formation, arterial dissection, and pleural effusion [11,17,42,52]. Similarly, the rate of minor complications has been reported to range from 2% to 56%, encompassing issues such as postprocedural pain, fever, and clinically silent coil migration [11,17,42,45,57].

Splenic infarction is a complication observed in 8.33% of cases following SAE, occurring more frequently after distal embolization [20,58]. The percentage of splenic volume infarcted varies depending on the extent and selectivity of the SAE. A higher grade of trauma is associated with an increased volume of infarction, with near-total and total splenic infarcts observed only in patients with AAST grade III injuries or higher [58]. Abscess formation occurs in 7.5% of cases involving near-total and total splenic infarctions. A splenic infarct volume of less than 50% generally does not lead to abscess formation. Management of total splenic infarction with abscess typically involves the placement of a percutaneous drainage catheter or surgical washout for cases that do not respond to percutaneous drainage [58]. A rare complication of splenic infarction is splenic rupture, which requires operative management [6].

Comparing various points of embolization along the splenic artery, embolization proximal to the dorsal pancreatic artery and between the dorsal pancreatic and great pancreatic arteries demonstrated a higher clinical success rate than embolization distal to the great pancreatic artery [59]. Embolization proximal but distal to the great pancreatic artery also showed reduced spleen perfusion rates compared to embolization proximal to the great pancreatic artery. No instances of pancreatic ischemia or pancreatitis were reported following embolization proximal to the dorsal pancreatic artery [59]. Given the theoretical risk of pancreatic ischemia with embolization proximal to the dorsal pancreatic artery, it is advisable to embolize between the dorsal pancreatic and great pancreatic arteries during proximal SAE.

Embolization with coils versus a gelatin sponge does not differ in terms of success rates or major complication rates, such as rebleeding that requires splenectomy [39,60]. One advantage of a gelatin sponge over coils is shorter procedural and fluoroscopy times [60]. However, proximal embolization with gelatin sponge has been associated with higher rates of minor complications, including abscess and necrosis, likely due to the development of segmental infarction [54]. A meta-analysis indicated a higher incidence of life-threatening complications with gelatin sponges compared to coils, leading to the recommendation that gelatin sponges be reserved for emergency situations where immediate hemorrhage control is necessary [53].

The impact of SAE on splenic volume remains a topic of debate. One study observed a decrease in spleen volume at 6 months post-embolization in patients with high-grade injuries [61]. Regarding the location of embolization, the study found no statistically significant association between either proximal or distal embolization and changes in spleen volume. Another study also reported reduced spleen volumes in patients who underwent SAE, though the differences were not statistically significant [62]. However, regarding the location of embolization, the study noted a reduction in spleen volume associated with distal embolization, but not with proximal embolization.

Altered red cell morphology, indicative of spleen dysfunction, was observed upon initial presentation following trauma but resolved at the 6-month follow-up [61]. Howell-Jolly bodies, which indicate damaged or absent spleen, were not observed after SAE [62]. This suggests that a decrease in spleen volume following embolization does not necessarily correspond to decreased splenic function and argues against the need for prophylactic immunization in patients undergoing embolization. Various changes in hematologic parameters were also noted after embolization [63]. A systematic review analyzing immune function in patients who have undergone SAE showed immune competency and recommended against routine vaccination [36]. Follow-up imaging after embolization for splenic trauma is recommended only in symptomatic cases [1].

The impact of SAE on immune function has been assessed by measuring immunoglobulin M (IgM) memory B cells, which are crucial for the immune response to encapsulated bacteria [64]. Patients who underwent SAE exhibited increased levels of IgM memory B cells compared to those who had a splenectomy. Distal SAE tended to preserve higher levels of IgM memory B cells than proximal embolization [64]. It is hypothesized that proximal SAE decreases the overall blood flow to the spleen, leading to ischemia or infarction in the splenic marginal zone where the majority of IgM memory B cells are located [64]. A review of various studies examining multiple aspects of splenic function concluded that splenic function is preserved following SAE, although no single parameter has been identified to assess overall splenic function comprehensively [65–67].

CONCLUSIONS

Splenic salvage has become a critical objective for patients with traumatic splenic injuries due to the spleen's significant role in immunologic protection. Patients with high-grade splenic injuries are typically managed nonoperatively if they are hemodynamically stable. Splenic artery angiography with embolization may be conducted in conservatively managed patients who exhibit clinical signs of ongoing hemorrhage. Proximal SAE can be utilized in patients with high-grade splenic injuries to reduce arterial perfusion pressure in the damaged arterioles and promote hemostasis. Distal SAE is indicated when active contrast extravasation is identified in a specific area, allowing for more selective arterial occlusion while preserving perfusion to the rest of the non-injured spleen. Patients retaining functional splenic tissue after trauma remain immunologically competent, and routine immunization against encapsulated organisms is generally not recommended.

Article information Continued