At the CT suite, the child has to be accompanied by an emergency physician or a senior pediatric intensivist or at least a pediatrician and a peripheral venous line must have been placed. Since the hemodynamics of a child are potentially very unstable, it is essential that the child has pulse and blood pressure monitoring. Installing on the scanner table is a crucial time. It is necessary to move the child with precaution, remove from the field of exploration all the metallic structures to avoid artifacts (ECG cables, electrodes…) (Fig. 25.2). The scan protocol should be chosen according to the weight of the child and the severity of the trauma (whole bodyscan, abdominal or thoracoabdominal acquisition).

A negative CT has a strong negative predictive value allowing a very early return home or even no hospitalization [12]. However, the impact of CT on the management is not always linked to the clinical status, but overall this examination allows a precise initial assessment of solid organs lesions as well as a conservative treatment. To be noted, the performance of CT for the detection off bowel and/or mesenteric lesions is lower than for solid organs.

Not uncommonly, children are transferred from a non-specialized pediatric center after an initial CE-CT. It is important to review these CT preferably by pediatric radiologists; this second interpretation can find discrepancies in more than 10% of cases including lesions not described or an increase in the severity of lesions [13].

It is of upmost importance that the pediatric exploration protocols remain recorded in the CT and can easily be adapted to the child’s weight in order to remain in the recommended doses:

Regarding the amount of iodine contrast media:

Oral contrast is not useful, characteristics for detecting intra-abdominal injury are similar between CE-CT with and without oral contrast [14].

MR imaging is very useful for monitoring abdominal trauma due to its performance and lack of ionizing radiation. It will surely have indications for the follow up of severe trauma (liver, spleen, kidneys) instead of CE-CT, in children who are old enough to avoid sedation (Fig. 25.3). In case of kidney trauma, MR urography will be performed allowing both the morphological and split renal function assessment [16]. MR cholangio-pancreatography is useful in some acute or delayed complications of liver or pancreatic trauma, in order to demonstrate bile duct injuries and estimate the origin of “collections” (bilomas or pancreatic cysts).

The use of MR imaging as first step for acute trauma is still limited because of the length of the examination, the need for child cooperation or sedation, and the difficulty to explore the whole body in case of severe trauma unlike CE-CT.

Despite all these limitations, the development of rapid abdominal sequences of about 10 s makes it possible to use MR imaging as a first-line exploration in the next future in addition to ultrasound, avoiding ionizing radiation.

Imaging aspects of liver trauma are the same in children as for adults. The initial diagnosis is made on CE-CT. It will depict accurately any hepatic laceration appearing as a hypodense area, with variable shapes. When the laceration reaches the capsular surface and breaks the capsule, there is an associated hemoperitoneum (Fig. 25.4). Subcapsular hematoma typically compresses the lateral margin of the hepatic parenchyma. The demonstration of active bleeding will influence the prognosis and has to be searched actively [17].

Conservative treatment is possible thanks to close follow-up by US with Doppler looking for acute or delayed vascular or biliary complications. AAST classification of liver injury is presented in Table 25.1.

Vascular or biliary complications are present in about 10% of cases.

Vascular complications include hemorrhage, hemobilia, arteriovenous fistula and pseudo-aneurysm, portal vein thrombosis, portal vein stenosis, Budd Chiari. They usually occur around day 15 and may progress asymptomatically or become complicated (hemorrhagic shock or portal hypertension). Their diagnosis is based on US with Doppler and CE-CT. Their treatment is conservative with the possibility of an endovascular treatment.

Biliary complications include fistulas, bilhemia, biloma, bilioperitoneum and stenosis of the biliary tract. The bilomas are present in 2–12% of hepatic trauma and their frequency increases with the severity of the trauma. Their discovery is delayed from day 15 to sometimes several years after the trauma and this is the first diagnosis to be evoked in case of any post-traumatic collection (Fig. 25.5). Spontaneous regression is usual for small bilomas (<3 cm); in case of persisting collection, percutaneous puncture, drainage or endoscopic surgery can be performed. The bilomas can become infected and also favor the development of pseudo-aneurysms. Bilio-peritoneum should be considered whenever an intraperitoneal effusion with stable hemoglobin is demonstrated. It conveys an infectious risk. The management by peritoneal drain and biliary prosthesis (endoscopically) is based on the “stent and drain” concept, which achieves satisfactory results in 90% of cases [18, 19]. Biliary stenosis is exceptional. It is secondary to direct trauma or traumatic pancreatitis. It exposes to the risk of cirrhosis. Diagnosis is based on US, MR cholangiography and endoscopic retrograde cholangiopancreatography (ERCP) (Fig. 25.5). It may be treated by drainage, balloon dilation and endoprosthesis.

Excluding multiple trauma, splenic trauma can be suspected during the initial US examination in the presence of a hemoperitoneum and a heterogeneous appearance of the spleen. The study of the spleen with a superficial probe is essential as well as the use of color Doppler. One of the indirect signs of splenic trauma is a globular aspect of the spleen with loss of visualization of its hilum. The more recent the trauma, the more discrete and even absent the US signs might be (Fig. 25.6). US usually underestimates the importance of splenic lesions. CEUS is very useful to depict traumatic spleen injury (Fig. 25.7).

In the case of a positive US, if the child is hemodynamically stable, CE-CT will confirm the lesions but above all will look for signs of severity (active bleeding in free peritoneum) and associated lesions. The sensitivity and specificity of CT in the detection of splenic injury is close to 100%. Splenic lesions are best displayed in the venous phase, and are usually represented by lacerations [17]. The presence of congenital clefts can lead to misinterpretation and false-positive patients. These congenital clefts have regular and homogeneous well-defined limits whereas the lacerations would appear more irregular.

In case of hemodynamic shock, FAST echo will be the only exam performed before surgical management.

The use of AAST grades for spleen trauma is not always easy with poor inter-observer reproducibility of this classification [20] (Table 25.2).

Long-term complications of conservative management are very rare (<1%) in contrast to early complications, which can occur in up to 15% [21] and mostly affect the older child.

It is therefore necessary to perform an early US follow-up with Doppler to look for these complications:

The time table of follow-up varies according to the teams and the grade of severity. In case of severe liver trauma, US follow-up can be: US at day 0, day 2, day 7, day of discharge and day 30. This follow-up US examinations should control the disappearance of the hemoperitoneum before day 7 signing the absence of active bleeding as well as the analysis of the spleen; it must include a color Doppler study in order to look for a possible pseudo-aneurysm. Some teams highlight the performance of CEUS [23]. These pseudo aneurysms are not so rare when searched systematically. Most of these pseudo aneurysms thrombose spontaneously after a few days but if they persist, embolization can be proposed (Fig. 25.8).