Diagnostic value of CT contrast extravasation for major arterial injury after pelvic fracture: A meta-analysis

Abstract

Purpose

We conducted a meta-analysis to determine diagnostic performance of CT intravenous contrast extravasation (CE) as a sign of angiographic bleeding and need for angioembolization after pelvic fractures.

Materials and methods

A systematic literature search combining the concepts of contrast extravasation, pelvic trauma, and CT yielded 206 potentially eligible studies. 23 studies provided accuracy data or sufficient descriptive data to allow 2x2 contingency table construction and provided 3855 patients for meta-analysis. Methodologic quality was assessed using the QUADAS-2 tool. Sensitivity and specificity were synthesized using bivariate mixed-effects logistic regression. Heterogeneity was assessed using the I2-statistic. Sources of heterogeneity explored included generation of scanner (64 row CT versus lower detector row) and use of multiphasic versus single phase scanning protocols.

Results

Overall sensitivity and specificity were 80% (95% CI: 66–90%, I2 = 92.65%) and 93% (CI: 90–96, I2 = 89.34%), respectively. Subgroup analysis showed pooled sensitivity and specificity of 94% and 89% for 64- row CT compared to 69% and 95% with older generation scanners. CE had pooled sensitivity and specificity of 95% and 92% with the use of multiphasic protocols, compared to 74% and 94% with single-phase protocols.

Conclusion

The pooled sensitivity and specificity of 64-row CT was 94 and 89%. 64 row CT improves sensitivity of CE, which was 69% using lower detector row scanners. High specificity (92%) can be maintained by incorporating multiphasic scan protocols.

Introduction

Approximately one in ten blunt trauma victims admitted to level 1 trauma referral centers sustain pelvic fractures [1]. Bleeding pelvic fractures are an immediate life-threatening injury associated with significant mortality [2], [3], [4], [5], [6], [7]. Rapid hemorrhage control is associated with improved survival [2], [8], but surgical decision making remains challenging due to difficulty determining the bleeding source [2], [4], [9]. Hemorrhage can arise from arterial injury, venous injury, or fractured bone ends [2], [5], [10]. Angioembolization and external fixation are the most common treatment pathways for hemorrhage associated with pelvic fracture, with each therapy aimed at addressing different sources of bleeding [2], [3], [11]. A central decision point critical to the timely and optimal deployment of appropriate resources and initial treatment strategies hinges on whether active arterial bleeding is present [2], [3], [12].

Early aggressive trans-catheter arterial embolization (TAE) is well established as an effective means of reducing transfusion requirement, complications, and mortality from arterial hemorrhage [2], [3], [4], [13], [14], [15], [16], [17], [18], [19], whereas low pressure bleeding from the rich pelvic venous plexus or fractured bone ends is best controlled through splinting, reduction of pelvic volume, and tamponade using external fixation [2], [3], [19], [20]. Contrast enhanced CT is the cornerstone screening exam for evidence of arterial bleeding in patients with pelvic fractures who are sufficiently stable for transport to a trauma resuscitation unit CT scanner [19]. In a recent epidemiologic study spanning 11 Level 1 trauma centers, CT was used in up to 85% of patients admitted in shock [2].

The Eastern Association for the Surgery of Trauma (EAST) practice management guidelines note that research has primarily focused on two imaging signs for determining need for TAE- CE and pelvic hematoma volume [19]. The latter has been difficult to measure reliably or efficiently at the point of care using diameter-based or manual segmentation techniques [21], [22], [23]. The EAST guidelines therefore emphasize CE as the most useful imaging predictor of the need for pelvic angiography and TAE in the clinical setting and recommend that patients with CE be considered for TAE regardless of hemodynamic status [19]. A number of studies have assessed the accuracy of CE for predicting angiopositivity or hemostatic intervention with TAE [19], however published sensitivities and specificities are highly variable [11], [19], [24]. Improvements in CT scanner technology should improve detection and characterization of bleeding, but there is speculation that improved image quality and temporal resolution with 64-detector row or higher CT scanners might also confound assessment due to increased detection of small self-limiting foci of CE [5], [9], [20], [24]. Dynamic characterization of CE using multiphase image protocols is thought to improve diagnostic certainty in such cases, but there are no comparative effectiveness studies assessing the diagnostic performance benefit of multiphase over single phase protocols. Our objectives were to a) establish pooled accuracy metrics of CT for predicting angiopositivity and need for TAE despite the wide variability described in the literature, and b) determine whether diagnostic performance improves with the use of 64 detector row CT and multiphasic protocols [9], [22],

We hypothesized that 64- or higher MDCT scanners and multiphasic protocols would improve diagnostic performance. We also sought to provide more precise estimates of the diagnostic performance of CE for predicting major arterial injury (defined by positive angiographic findings and use of TAE for hemorrhage control). Several potentially confounding aspects of study design were investigated as sources of heterogeneity in the published results.