Our study demonstrated the long-term incidence and timing of SPA formation after blunt splenic injury treated with NOM. Five of 49 patients developed SPA during the follow-up period, and delayed rupture was not observed in our study cohort. The incidence of delayed SPA formation was in agreement with the findings of previous studies[8, 15, 18, 19]. We believe that our study reports two clinically important findings: The first finding was that SPA formation occurred within 15 days (range, 8–15 days). The second finding was that TAE application during hospital admission tended to reduce the formation of SPA.
Most cases of delayed SPA formation were detected approximately within a week of injury[8, 15]. Based on these data, some studies recommend performing follow-up CT approximately a week later after injury[15]or within 48 hours after admission[18]. However, the timing of SPA formation in our study was later than that reported in published studies. This finding suggests that performing follow-up contrast-enhanced CT after approximately 2 weeks, in addition to performing one at 48 hours or at 1 week, might be a useful approach to evaluate delayed formation of SPA. This difference might have been due to the variation in patients’ severity. The guideline states that hemodynamically unstable patients should be managed with urgent laparotomy[2]. According to the guidelines, previous studies[8, 15, 18] were limited in terms of the adaptation of NOM to hemodynamically stable patients. Compared with them, NOM for TAE was chosen even in patients with hemodynamic instability in our institution. Due to this difference in NOM indication, more severe patients might have been included in this study. In fact, the median value of ISS was 30 in our study, and this value tended to be higher than that reported in previous studies[8, 18]. Moreover, our finding suggested that performing routine follow-up CT after approximately 2 weeks of injury may not be necessary. In previous studies[8, 15], the maximum period for follow-up CT was limited to within 25 days because follow-up CT was performed during only intensive care unit stay or hospital stay. In contrast, we performed follow-up contrast-enhanced CT in 32 of 49 patients for more than 2 weeks, for up to 1170 days, even if the patient had been discharged. However, no patient developed SPA after 15 days.
The trauma severity in patients with emergency TAE was more severe than that in patients without the emergency TAE. Nonetheless, patients who received the emergency TAE tended to have a lower incidence of delayed SPA formation than those who did not receive the emergency TAE in our study. Although the incidence of SPA formation was not significantly different between the two groups, emergency TAE might have an essential role in preventing subsequent SPA formation. This result was supported by the fact that adjunctive TAE improved NOM success rates[4–6] and that SPA rupture was the main cause of NOM failure[8]. Indeed, the NOM failure rate in all patients in this study was 2.0% (1 of 49 patients), which is lower than that of 8.3% (95% confidence interval, 6.7–10.2) reported in a previous meta-analysis[7]. This discrepancy may have been due to differences in the initial TAE indication. In our institution, emergency TAE is generally performed even for grade Ⅲ injury patients. Briefly, emergency TAE is also applied to patients who should have undergone laparotomy according to the guideline. This inclusion criterion is slightly more aggressive than the EAST guideline recommendation[2]. By contrast, the previous meta-analysis[7] included observational studies wherein TAE was not applied for high-grade injury patients. Therefore, a large prospective observational study or a randomized controlled study is needed to confirm the utility of TAE to prevent SPA formation.
This study had several limitations. First, our study had a retrospective descriptive design, and we did not follow any strict protocol for NOM management and TAE indication. Decision making for TAE induction depended on the physician’s discretion. Consequently, patients with more severe conditions might have been managed by NOM together with TAE instead of operative management in the present study compared to that in previous studies. Therefore, caution should be exercised during the generalization of our findings in terms of the incidence and timing of SPA formation. However, the incidence of SPA observed in this study was in agreement with that of previous studies[8, 15, 18, 19]. Hence, we believe that our findings can be applied to most patients with blunt splenic injury, even though the strategy followed was slightly different. The second limitation was the variation in the timing and frequency of performing follow-up CT. In our institution, patients considered to be at high risk of SPA formation (e.g., high-grade injury or presence of CB at the initial CT) tended to have a long follow-up period. While this trend was reasonable in clinical practice, we could not set the schedule of the follow-up CT at a constant timing. Some patients did not visit our institution, which might lead to withdrawal bias. In fact, among all 49 patients, follow-up CT over 60 days was performed only in 20 patients in our analysis. However, we could conduct the follow-up for approximately 70% of patients for more than 2 weeks, and SPA formation was not detected after 15 days from injury onset. This effect of withdrawal bias was considered to be small. The third limitation was the small number of eligible patients and the single-center study. Therefore, the results of this study may not be generalizable to other settings.
Despite these limitations, this study has strengths, as it was the first observational study to evaluate the long-term clinical history of SPA after blunt splenic injury treated with NOM by utilizing long-term repeat contrast-enhanced CT. Thus far, no previous studies have conducted follow-up contrast-enhanced CT for patients until after discharge or confirmed whether SPAs were formed in the long-term. Our findings may have clinical implications in terms of the duration of follow-up CT in case of blunt splenic injury treated with NOM. A large-sample, multicenter prospective trial is warranted to confirm our findings.