Radiol med (2015) 120:3–11 DOI 10.1007/s11547-014-0455-3

EMERGENCY RADIOLOGY

The role of CEUS in the assessment of haemodynamically stable patients with blunt abdominal trauma Fabio Pinto · Massimo Valentino · Laura Romanini · Raffaella Basilico · Vittorio Miele 

Received: 4 July 2014 / Accepted: 14 July 2014 / Published online: 21 August 2014 © Italian Society of Medical Radiology 2014

Abstract Computed tomography (CT) still represents the preferred imaging method in the assessment of patients presenting with multiple trauma. Nevertheless, in patients with low-energy abdominal trauma, the use of CT is debated because of the possible unnecessary radiation exposure. Accordingly, conventional ultrasound (US) imaging has been increasingly employed as the initial imaging modality in the workup of minor traumatic emergency conditions. Focused assessment with sonography for trauma is widely used to detect free intra-abdominal fluid, but its role is controversial, because the absence of free fluid does not exclude the presence of injuries to abdominal organ. Injection of an ultrasound contrast agent (UCA) may give the radiologist relevant additional information to that obtained with conventional US. Thus, in trauma patients, following early assessment with conventional US imaging, a contrast-enhanced US (CEUS) can provide a more reliable evaluation of solid organ injuries and related vascular F. Pinto (*)  Department of Diagnostic Radiological Imaging, Marcianise Hospital, ASL Caserta, CE, Italy e-mail: [email protected] M. Valentino  Diagnostic Radiology Department, S. Antonio Abate Hospital, Tolmezzo, UD, Italy L. Romanini  Istituto di Radiologia, Policlinico S. Matteo, Universita’ di Pavia, Pavia, Italy R. Basilico  Istituto di Radiologia, Universita’ di Chieti, Chieti, Italy V. Miele  UOC di Diagnostica per Immagini Cardiovascolare e d’Urgenza, Azienda Ospedaliera S. Camillo-Forlanini, Rome, Italy

complications, including active bleeding, pseudoaneurysms, and artero-venous fistulas. CEUS cannot replace abdominal CT, but it represents a noninvasive and repeatable imaging tool capable of providing a reliable assessment of trauma severity and expedite the patient’s treatment. Keywords  Ultrasound · Contrast media · Trauma · Emergency radiology

Introduction On admission, patients with blunt abdominal trauma are usually investigated with US to exclude the presence of free abdominal fluid [1, 2]. This method is referred to as Focused Assessment with Sonography for Trauma (FAST), and it has been formally incorporated into the trauma protocol [1, 3, 4]. FAST enables a reliable identification of haemoperitoneum: its sensitivity, specificity, and overall accuracy in detecting free fluid have been reported to be 81–94, 88–100, and 86–98 %, respectively [4, 5]. However, this technique requires the operator’s expertise [6]; moreover, injuries to solid organs can be overlooked at conventional US and free abdominal fluid may be missing in patients with traumatic abdominal injuries. Accordingly, to provide a complete assessment of patients sustaining severe trauma, contrast-enhanced CT represents the most used and sensitive imaging modality [7]: nevertheless, to decrease unnecessary radiation exposure, a limited use of CT in selected series, such as paediatric patients, females of reproductive age and low-energy trauma patients has been advocated [5]. To overcome this dualism, in the last decade, a new US technique has been developed using new generation US contrast agents (UCAs) [8–12], with the possibility of recognising or excluding abdominal solid

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Fig. 1  18-year-old male admitted to hospital after a motor vehicle accident: a conventional ultrasound (US) shows an inhomogeneous hyperechoic area in the right lobe of the liver. b Contrast-enhanced US (CEUS) scan in the same position shows a large hypoechoic area due to a parenchymal laceration. c Computed tomography (CT) with contrast medium (CECT) confirms the diagnosis

organ injuries and assessing their location and size [13]. After illustrating the CEUS findings of traumatic injuries to abdominal organs, this review article will discuss the possible role of this technique in the assessment of blunt abdominal trauma in the stable patient.

Contrast‑enhanced ultrasound (CEUS) Technique UCAs commonly used in our practice consist of stabilised gas microbubbles, of 1–10 μm of diameter, surrounded by a phospholipid shell [14]. In our institutions, as a protocol, CEUS imaging follows conventional US examination in the assessment of blunt abdominal trauma [15]. The patient is initially evaluated by US for free fluid and organ abnormalities. Then a bolus of 1.2–2.4 mL of UCA is administered, depending on available equipment, followed by a 5- to 10-mL saline flush via a cannula in the antecubital fossa. To avoid the rupture of the bubbles, the focus is set to the deepest insonated area. A total of 3–6 min is required for investigating all the solid abdominal organs

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(liver, pancreas, spleen and kidneys). The examination is stored as a movie and can be carefully evaluated at the end of the procedure. The CEUS technique can be carried out in a variety of scenarios, including bedside, operating room, and trauma suite. In traumatised patients, whenever necessary, the contrast material injection can be repeated to clarify a parenchymal area that has initially proved unclear. CEUS skills can be acquired after 40–50 examinations, after which most radiologists become confident in the technique [16]. Normal abdominal organ enhancement Microbubbles are blood pool agents that remain within the vessels, both in macro- and in micro-vascularity without interstitial extravasation. This feature, in addition to specific software using dynamic low mechanical index (MI) [17], enables differentiation of the signal between background tissue and gas-filled microbubbles, without bursting the latter. CEUS findings mainly overlap those obtained at CT and magnetic resonance (MR) during arterial phase imaging, but there is no similarity in the venous and the delayed phases, because CT and MR contrast

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Fig. 2  41-year-old female with direct trauma: a US shows an inhomogeneous area in the hepatic parenchyma associated with a subcapsular haematoma. b CEUS shows grade III traumatic laceration of the liver and clearly depicts the parenchymal and subcapsular haematoma. c, d CE-MDCT confirms the CEUS findings, showing the

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hepatic lacerations, with subcapsular and parenchymal haematoma. e 3 months later, the follow-up T1-weighted magnetic resonance (MR) sequence with fat suppression shows the well-demarcated haematoma, surrounded by an hyperintense rim, due to fibrous reparative tissue

media spread out into the extravascular interstitium. At CEUS, the arterial phase starts approximately after 10– 20 s and proceeds up to 30–40 s. This phase is followed by the venous and the late phases, in which the contrast agent is distributed to the whole capillary bed and the concentration slowly decreases followed by the removal of contrast agent through the lungs. The venous and the late phases last in the range from 2 to 6 min, varying in each abdominal parenchyma. While inaccurate timing of CT or MR acquisition phases may result in the inadequate characterisation of a focal parenchymal injury, CEUS allows continuous depiction of the lesion through all the vascular phases.

>90mmHg), uncontrolled systemic hypertension, and patients with adult distress syndrome. UCAs are widely marketed and used in the clinical practice throughout Europe and in some eastern Asian countries. Recently, UCAs have been approved in the USA for cardiac and trauma evaluation [18, 19]. UCAs are usually well tolerated, and serious reactions have been seldom reported [20–22], with only 1:7,000 (0.014 %) anaphylactoid reactions, rates lower than the equivalent of CT contrast agents (0.035–0.095 %). They are not licenced in pregnancy and also breastfeeding represents another contraindication in some countries [23]. The use in paediatric patients and in those younger than 18 years old is not allowed at the moment. UCAs do not interact with Contraindications and adverse reactions the thyroid gland. Finally, because of absence of renal excretion, they are Major contraindications include right-to-left shunts, severe not nephrotoxic, so that UCAs can be safely employed in pulmonary hypertension (pulmonary artery pressure  patients with renal insufficiency.

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Fig. 3  10-year-old female with direct trauma: a US shows wide inhomogeneity of the splenic parenchyma. b CEUS well demonstrates a large lesion of the lower pole. c, d Axial and coronal CE-MDCT images confirm a large lesion of the lower pole of the spleen; huge haemoperitoneum

CEUS imaging of abdominal traumatic injuries

hypoechoic regions without mass effect or vessel displacement (Fig. 2).

Liver Spleen Timing in liver enhancement starts with an initial arterial phase (at 15–25 s). Because of its dual vascular supply, the hepatic phases after the arterial phase include the portal phase (30–120 s after contrast injection) and the sinusoidal (or late) phase (120–300 s after contrast injection) [24]. Overall, the portal phase is the most effective for investigating any suspected traumatic injury [23]. As in CT, active extravasation is considered when there is evidence of contrast agent collection with echogenicity similar to that of an adjacent vessel. At CEUS, hepatic injuries are shown as enhancement defects, sharply demarcated from the intensely enhanced, undamaged hepatic tissue. Traumatic lacerations are recognisable as hypoechoic bands (Fig. 1), linear or branched, sometimes perpendicular to the organ capsule, whereas parenchymal contusions or subcapsular haematomas appear as in homogeneous

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The spleen shows a strong but persistent enhancement (up to 6 or to 8 min): the injected microbubbles are retained within the parenchyma so that nonperfused parenchyma can easily be detected during the late-phase scanning. It is the most frequently affected parenchymal organ if a lowvelocity abdominal trauma occurs in childhood (Fig. 3). In patients with splenic trauma, CEUS may also display further findings that can be missed at conventional US imaging, including active bleeding and pseudoaneurysms (Fig.  4) [25–27], which are visualised in the early stages as extravasation of microbubbles into the parenchyma or as perivisceral haematomas, respectively (25–30). Conventional US can initially miss a splenic injury and/or underestimate its extent, in particular if haemoperitoneum is absent (Fig. 5).

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in series including all grade injuries [28, 29, 32]. Although UCA injection does improve the sensitivity of conventional US imaging for identification of renal injuries, the role of this technique has to be still clarified: in fact, injury to the renal collecting system may be overlooked at CEUS because of a lack of urinary excretion of microbubbles. Pancreas After the contrast agent injection, the pancreas shows a mounting enhancement of its intensity. Pancreatic disruption or laceration (Fig. 7) can appear as anechoic and hypoechoic perfusion defect areas at both arterial and parenchymal phases, sometimes associated with fluid collections. These findings can be missed at conventional US examination. Injury to the pancreas is relatively uncommon, occurring in

The role of CEUS in the assessment of haemodynamically stable patients with blunt abdominal trauma.

Computed tomography (CT) still represents the preferred imaging method in the assessment of patients presenting with multiple trauma. Nevertheless, in...
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