There is growing evidence that most of these injuries heal spontaneously or stabilize without further compromising the distal circulation and perfusion [6].

Vascular injuries may be initially undiagnosed in hemodynamically stable patients, so a detailed clinical history including the mechanism of the trauma is important. Factors that can jeopardize diagnosis of acute vascular injuries usually are the presence of distraction injuries, lack of correlation with clinical presentation, radiologist experience, or inadequate CT scan protocol [7].

Subclinical vascular injuries with intact distal perfusion may be observed with serial monitoring, antiplatelet therapy or systemic anticoagulation, and repeat noninvasive imaging [8].

Subclinical vascular defects have been defined as those exhibiting the following characteristics:

The liberal use of imaging in the presence of any hard sign to confirm or exclude vascular injury is recommended [4].

Most hard signs in this setting (as much as 87%) are not due to vascular injury, but rather to soft tissue and bone bleeding, traction of intact arteries with pulse loss, or compartment syndrome [9].

If significant vascular injuries (such as occlusion, extravasation, or transection) are excluded, the treatment of soft tissue and skeletal injuries may proceed. How reperfusion is achieved depends on the patient’s hemodynamic status, physiologic parameters, skeletal stability, wound characteristics, and resource availability [10].

Vascular imaging is mandatory when expectant management is chosen, but resolution can be seen in 85–90% of these lesions with no operative intervention [11].

Doppler Ultrasound (DUS) has shown an overall accuracy of 98% for diagnosing vascular injury, but it requires time and high experience [1].

DUS provides additional information on clinical examination but there is not consensus in the literature about its importance in the diagnostic management in the injuries of the limbs in trauma patient. DUS can be obtained rapidly and used to detect occlusion, intimal flaps, and luminal defects [12].

For the lower limbs evaluation a DUS assessment should be done also to confirm the absence of pedal pulses and to perform an ankle-brachial index (ABI) when possible. In emergency traumatic setting, an ABI is useful for the evaluation of a patient who is at increased risk for lower extremity arterial injury: an ABI < 0.90 suggests a need for further vascular imaging, whereas an ABI > 0.90 decreases the likelihood of an arterial injury, and the patient may be observed with serial ABI assessments or may undergo a vascular study on a delayed basis [13].

DUS has some diagnostic limitations in locating the exact point of artery cutoff point and the traumatized area. Moreover, the DUS evaluation of the vascular limbs injuries, especially in trauma patients, requires high level of expertise; it is highly operator dependent and can be time-consuming [14].

Large retrospective reviews have shown that Computed Tomography Angiography (CTA) significantly increases the probability of survival in polytrauma patients [15].

It has the added advantage of simultaneously being able to assess extensive body areas as well as demonstrating associated soft tissue and bony injuries.

CTA has dramatically improved over the last few years and has overtaken catheter angiography as the initial first choice diagnostic tool in the trauma patients [4].

While traditional angiography has been the gold standard and affords opportunity for intervention, the ability to rapidly acquire high-specificity diagnostic imaging with spiral CTA has been a game changer as a rapid screening test and plays a major role in the management of multi-trauma patients.

Digital Subtraction Angiography (DSA) is the diagnostic standard for vascular injury and allows for therapeutic intervention [16].

CTA has a sensitivity of 90–95% and specificity of between 98% and 100% for the detection of upper and lower limbs arterial injuries [16]. CTA may be limited by poor arterial opacification, motion artifact, streak artifact from adjacent metallic fragments, or slowing of flow beyond injured sites [16]. CTA has nowadays replaced catheter angiography as the primary imaging technique to evaluate patients with suspected acute vascular injuries [7, 10, 17]. Nevertheless, some investigators still recommend DSA as the primary imaging test, particularly in patients with finding of metallic fragments or shrapnel on conventional imaging to avoid technical artifacts which may render affected vascular segments non-diagnostic on cross-sectional images [18]. However, in this set, DSA requires an highly trained team readily available at the time of patient admission, it is costly and it is not free from the possibility of serious complications due to catheter insertion, especially in an artery with local hematoma formation, vessel thrombosis and, in more severe cases, post-angiography dissection, embolization and pseudoaneurysm formation [19–21].

CTA pledge the acquisition of three-dimensional images with submillimetric spatial resolution of the entire body, from head to foot in only a few seconds with a single contrast bolus, and state-of-the-art workstations allow Multiplanar Reformations (MPR), Maximum Intensity Projection (MIP), and Volume Rendering (VR) reconstructions [10, 21–24].

It is of fundamental importance the appropriate selection of scan parameters and CT protocols. It is consolidated knowledge that acquiring images in arterial phase improves the detection of arterial injures, AVF, and PSA while the venous phase is essential to detect venous injuries and to differentiate contained vascular injures from actively bleeding lesions. Therefore, both phases should be routinely included in the whole-body CT evaluation of patients with deceleration injury [17].

All studies should be performed with multiphasic, high-resolution protocol, slice thickness and reconstruction interval value of about 1 mm, before and after administration of intravenous, highly concentrated contrast media (350–400 mgI/mL, with a 3.5–5 ml/s infusion rate, followed by a 25–50 ml bolus of isotonic saline at the same flow rate). The field of view (FOV) should be the smallest including both limbs, to minimize the isotropic voxels and to allow evaluation of symmetry of contrast material arrival time and symmetry of flow. The scan coverage should include both the proximal and distal joints to the region of suspected injury. All study should be performed under the supervision of a radiologist, to evaluate any need of additional late phases. An automated bolus tracking, with region of interest placed at the diaphragmatic aorta (for whole-body scanning) at an attenuation threshold of 100HU, is suggested to time the beginning of the arterial phase, in order to avoid poor timing of the contrast material bolus or bolus outrun [10, 17, 21]. Three-dimensional multiplanar reconstructions and maximum intensity projection should be routinely performed to facilitate recognizing the vessel anatomy and look for possible injuries [10, 17, 21].

Many different vascular injuries can be detected. Active arterial hemorrhage or extravasation can be defined as extravascular contrast media leakage, recognized as hyperattenuating regions with density similar to that of the arteries. Dissection is the evidence of an intraluminal flap with intramural extension of intravenous contrast material. Arteriovenous fistula formation is a communication between an artery and an adjacent vein, with premature venous enhancement. Pseudoaneurysm is a well-contained accumulation of contrast material-enhanced blood beyond the confines of the arterial wall. Narrowing of an artery is an abrupt change in caliber of the vessel within the area of traumatic injury with maintained patency while occlusion of an artery is an abrupt complete termination of an artery. Vessel transection is seen as an abnormality in the vessel contour due to full thickness laceration with free contrast extravasation detectable in the arterial phase [10, 17].

Hemodynamic instability in limbs injuries is more often associated with Penetrating Extremity Trauma (PET) or exposed fractures. In a 14 patient series who died from isolated limb PET, 70% occurred to the lower extremity and 86% were proximal to the elbow and knee [25].

A patient in shock with PET belong in the operating room and no diagnostic studies, except X-rays of the chest, pelvis and the involved extremity are indicated. If there is no inspective evidence that an arterial injury is present but clinical evidence is still strongly suggesting so, DUS, MDCT or DSA can be obtained [8, 14, 26, 27].