20 Abdominal Traumas
Emilio Quaia
E. Quaia, MD
Department of Radiology, Cattinara Hospital, University of Trieste, Strada di Fiume 447, 34149 Trieste, Italy
is clinically suspected despite negative US findings (Brown et al. 2001), and it is generally performed only in hemodynamically stable patients. Anyway, contrast-enhanced CT presents a lower sensitivity compared with US in detecting abdominal free fluid (Poletti et al. 2003) and presents higher costs and radiation exposure.
Diagnostic peritoneal lavage to clarify free fluid has been replaced in Europe by US and CT. If a large amount of free fluid is found and the patient is hemo- dynamically unstable, an emergency laparotomy is performed (Zügel et al. 2004).
20.2
Baseline US
The first post-traumatic lesion in abdominal organs is parenchymal contusion, which is defined as an area of abnormal vascularization and edema, but with only little collected hemorrhage (Dondelinger et al. 2004).
Parenchymal contusion appears as a hypoechoic area which does not show any signal of perfusion at color or power Doppler US (Dondelinger et al. 2004).
Acute hematoma appears as a hyperechoic rounded lesion with sharp margins at baseline US. When the location is subcapsular, the shape of hematoma is lenticular and the normal hepatic parenchyma is dis- placed centrally (Dondelinger et al. 2004). When clot organization is completed, the hematoma pres- ents an anechoic pattern if the clot lysis is prevalent or a calcific pattern with posterior acoustic shadowing if the solid component persists.
Parenchymal tear or laceration is defined as a parenchymal interruption without connection to the opposite margins. Parenchymal fracture is defined as a complete parenchymal interruption with opposite- margins connection. Abdominal free fluid is always present in parenchymal laceration or fracture. Both parenchymal tears and fractures appear as hypere- choic bands, lines, or stellate strands (Dondelinger et al. 2004).
CONTENTS
20.1 Introduction 295 20.2 Baseline US 295
20.3 Contrast-Enhanced US 296
20.4 When Microbubble-Based Agents Should Be Employed 299
References 299
20.1
Introduction
Abdominal ultrasound (US) is useful in screening for injury in patients with blunt abdominal trauma, and it presents high (82–96%) sensitivity (Poletti et al. 2003) and high (94–100%) specificity (Kimura and Otsuka 1991; McKenney 1999; Dondelinger et al. 2004) to detect free fluid in blunt abdominal trauma. On the other hand, the sensitivity of US is very low (40–55%) for directly demonstrating organ injury (Poletti et al. 2003).
The detection of free intraperitoneal fluid by US is considered very useful in hemodynamically unstable patients, while the value of US in hemo- dynamically stable patients is not clear for the large percentage of organ injuries that are not associated with free fluid (Shanmuganathan et al. 1999;
Poletti et al. 2004); however, the combination of negative US findings and negative clinical observa- tion virtually excludes abdominal injury in patients who are admitted and observed for at least 12–24 h (Sirlin et al. 2004).
Contrast-enhanced computed tomography (CT) is the reference imaging procedure for diagnosing traumatic abdominal injuries (Poletti et al. 2002;
Huppert 2004). Contrast-enhanced CT is used when
screening US findings are positive or when injury
Fig. 20.1a,b. Splenic laceration. At baseline US (a) the spleen (arrows) appears diffusely heterogeneous. At contrast-enhanced US (b) an avascular wedge-shaped parenchymal zone becomes evident.
a b
US improves the visibility of injuries in all abdomi- nal parenchymas, the spleen (Figs. 20.1, 20.2), the liver (Fig. 20.3), and the kidneys (Fig. 20.4; Poletti et al. 2004). Microbubbles injection improves the visibility of parenchymal hematoma, lacerations, and fractures (Fig. 20.2), by increasing the contrast resolution in comparison with the adjacent normal parenchyma. In fact, after microbubble-based agent injection, hematoma appears as a hypovas- cular intraparenchymal lesion, while parenchymal fracture and lacerations (Figs. 20.1, 20.3) appear as wedge-shaped avascular zones. Post-traumatic lesion of the hilar branches of the main renal artery may determine focal perfusion defects in the renal parenchyma appearing as hypovascular wedge- shaped lesions (Figs. 20.4).
Even though the improvement in visibility of abdominal organs injuries is improved after micro- bubble injection, if compared with baseline US, some recent clinical studies showed clear limita- tions of contrast-enhanced US in detecting paren- chymal injuries in hemodynamically stable patients (Poletti et al. 2004). The only exception was the intraparenchymal pseudoaneurysms from vascular injuries which appear as focal pooling of microbub- bles (Fig. 20.5) in the injured parenchyma correlat- ing with contrast extravasation in CT (Catalano et al. 2003; Poletti et al. 2004). Contrast-enhanced US was found effective also in revealing the active bleeding in the injured spleen, liver and kidney
parenchyma, and in abdominal aortic aneurysm rupture. Active contrast medium extravasation is a known angiography and CT sign of ongoing bleed- ing. Owing to the current possibilities of real-time, contrast-specific US systems, it is now possible to detect contrast leakage by using contrast-enhanced US, frequently the first image option in screening patients with abdominal emergencies (Cusati et al.
2004). At contrast-enhanced US, the active bleeding appears as a subcontinuous hyperechoic jet which tends to pool dependently. It should be differenti- ated from calcifications, opacified normal vessels, small pseudoaneurysm, and still-vascularized areas within injuries parenchyma (Cusati et al. 2004).
Some studies have reported the high accuracy of contrast-enhanced US in the visibility of parenchy- mal lesions in children (Oldenburg et al. 2004), in whom the splenic injury is the most common com- plication in blunt abdominal traumas. Even though contrast-enhanced CT is the most accurate imaging procedure to identify splenic injuries (Krupnick et al. 1997), US has several advantages over CT in children, such as the absence of radiation (particu- larly important in children), lower costs, no seda- tion, and the possibility of imaging at the bedside (Oldenburg et al. 2004).
fracture (arrows).
a b
c d
Fig. 20.3a–d. Liver laceration in a 33-year-old man after a motorbike accident. At baseline power Doppler US (a) a heterogeneous area (arrows) is identifi ed in the liver parenchyma. At contrast-enhanced US a liver parenchyma laceration becomes evident (arrows) in different scan planes (b,c). Contrast-enhanced CT (d) confi rms liver laceration (arrow).
a b
c d
a b
c d
Fig. 20.4a–d. Post-traumatic renal perfusion defects in a 32-year-old woman after a car accident. Immediately after the accident, the patient revealed hematuria. a–c At contrast-enhanced US a wedge-shaped renal perfusion defects (arrows) is evident in renal parenchyma after microbubble injection. Contrast-enhanced CT (d) reveals a similar fi nding (arrow) also with evidence of renal parenchyma interruption. A small and covered renal parenchyma laceration was found at surgical laparoscopy.
Fig. 20.5a,b. a Intraparenchymal focal pooling of microbubbles from vascular injuries in splenic trauma. b Contrast-enhanced CT revealed contrast extravasation at arterial phase 30 s after iodinated agent injection. (Courtesy of O. Catalano)
a b
20.4
When Microbubble-Based Agents Should Be Employed
The employment of microbubble-based agents in the abdominal traumas is not still defined. Microbub- bles should be employed in hemodynamically stable patients, without or with evidence of free fluid at baseline US, to improve the accuracy of US in detec- tion of parenchymal injuries. Contrast-enhanced US has been showed to be particularly useful to detect splenic injuries in children, principally for the absence of radiation and sedation (Oldenburg et al. 2004). Moreover, some recent studies have shown the low accuracy of contrast-enhanced US in detect- ing organ injuries (Poletti et al. 2004), except for the depiction of delayed splenic pseudoaneurysm from trauma. According to these studies, contrast- enhanced US cannot be recommended to replace CT in the triage of hemodynamically stable patients with negative findings on abdominal US at admis- sion (Poletti et al. 2004).
In conclusion, contrast-enhanced CT still has to be performed if free fluid or pathological findings are shown by US. In hemodynamically unstable patients surgical laparoscopy remains the unique procedure.
References
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Catalano O, Lobianco R, Sandomenico F, Siani A (2003) Splenic trauma: evaluation with contrast-specific sonography and a second generation contrast medium: preliminary expe- rience. J Ultrasound Med 22:467–477
Cusati B, Catalano O, Nunziata A (2004) Contrast medium
extravasation as an indicator of active bleeding: demon- stration with contrast-enhanced sonography (abstract).
RSNA 2004
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