Article, Radiology

A patient with a transient high-density area on computed tomography in juvenile lung injury

Case Report

A patient with a transient high-density area on computed tomography in juvenile lung injury

Abstract

An 8-year-old boy was struck by a truck, and the impact carried him 10 m away from the scene. On arrival at the hospital, his chest and left thigh roentgenograms revealed fractures of the left clavicle, scapular, and left femur shaft. His chest computed tomography scan demonstrated right domi- nant bilateral multiple ill-defined and hazy ground-glass density areas 70 minutes after the accident. He was treated with Conservative therapy with 2 L/min of oxygen. On the fourth hospital day, the chest computed tomography scan revealed the disappearance of most of the pulmonary lesions. Based on the natural time course of pulmonary contusions, it was impossible to explain why most of the pulmonary lesions in this patient disappeared within 4 days. A transient malfunction of the blood-gas barrier in the alveoli induced by blunt trauma might lead to the generation of lung edema.

The histopathological pattern of pulmonary contusions involves the disruption of alveoli, with consequent intra- alveolar and interstitial edema and hemorrhage [1]. They are most frequently bilateral and multiple, particularly in young patients, both in the impact and contrecoup areas. Pulmonary contusions are generally located subpleurally, in the periph- eral region of the lung. Computed tomography (CT) allows for earlier identification of lung contusion than do plain roentgenograms because of its high contrast resolution. The CT patterns for pulmonary contusions are ill-defined and confluent areas of hazy ground-glass density, without air bronchograms and with no anatomical repartition [1]. In children, these predominantly subpleural regions have been reported as subpleural sparing [2]. Computed tomography examinations usually reveal complete resolution of pulmon- ary contusions, without sequelae, within 1 to 2 weeks after the trauma [1]. However, in one patient, the pulmonary lesions induced by a blunt chest trauma observed on CT completely disappeared 4 days after the trauma. This report explores the hypothesis that some pulmonary lesions induced by blunt trauma that are detected by CT are pulmonary edema.

An 8-year-old boy was struck by a truck and thrown 10 m from the scene. When the emergency medical technicians

arrived, his oxygen saturation at Room temperature was 92%. He was transported to the hospital and arrived 30 minutes after the traffic accident. He had no particular past or family history. On arrival, he showed clear consciousness, and his vital signs were stable. He had scrubbing wounds on the face and the right and left knees and showed a deformity of left thigh. His oxygen saturation after administration of 10 L/min oxygen was 100%. The biochemical analysis of the blood and urine did not indicate specific injuries. His chest and left thigh roentgenograms revealed a fracture of the left clavicle, scapular, and left femur shaft. His chest CT (Aquilion TSX- 101A; Toshiba, Tokyo) demonstrated right dominant bilat- eral multiple ill-defined and hazy ground-glass-density areas (Fig. 1A) 70 minutes after the accident. He underwent conservative therapy with 2 L/min oxygen. On the second day in the hospital, his oxygen saturation was 100% with room air. On the third day in the hospital, a blood gas

analysis showed the following: pH 7.476; PCO2, 30.0 mm Hg; PO2, 100.0 mm Hg; HCO 22 mmol/L; and base excess,

3

-1.5 mmol/L. On the fourth day in the hospital, chest CT

revealed the disappearance of most of the pulmonary lesions (Fig. 1B). He underwent an internal fixation for the left femur fracture on the eighth day in the hospital and was moved to the orthopedic ward on the 11th day without any respiratory problems.

After pulmonary contusions, the tissue shows diffuse areas of intra-alveolar hemorrhage with disruption of the alveoli, followed by local and systemic inflammation. Systemic levels of chemokines are increased and correlate with increased levels of chemoattractants for inflammatory cells. As a result, 24 hours after a contusion, a predominant neutrophic pattern of leukocyte infiltration is apparent in the alveolar spaces. At 48 hours, thickening of the alveolar lining with a continuing leukocytic infiltration is apparent along with intra-alveolar edema [3]. These areas form bronchiolitis obliterans organizing pneumonia-associated fibrosis at 7 days [4]. Therefore, it was impossible to explain why the patient showed the disappearance of most pulmonary lesions within 4 days.

Interestingly, in a unilateral open-lung injury model, a contralateral peripheral lung edema, apart from the region that underwent mechanical impact, is observed within 24 hours by both morphological observation and measurement of the wet-to-dry weight [5]. These indirect lesions are thought to be generated by a systemic inflammatory reaction.

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249.e4 Case Report

Another possibility is that the transient pulmonary lesions were a transient malfunction of the blood-gas barrier in the alveoli. The lung is particularly vulnerable to injury because the blood-gas barrier is extremely thin [7]. Accordingly, mechanical insult may cause a malfunction of the blood-gas barrier and lead to the formation of lung edema. The occurrence of such a mechanism was reported in (1) high-altitude pulmonary edema, (2) Neurogenic pulmonary edema, (3) severe left ventricular failure, (4) mitral stenosis, and (5) overinflation of the lung [7]. However, this mechanism has not been proven clinically or experimentally in the trauma setting; therefore, further examinations are warranted.

Youichi Yanagawa MD, PhD

Department of Traumatology and

Critical Care Medicine National Defense Medical College (NDMC)

Saitama 359-8513, Japan E-mail address: [email protected]

doi:10.1016/j.ajem.2008.05.027

References

Fig. 1 Time course of pulmonary lesions on CT. (A) On arrival at the hospital, the chest CT demonstrates bilateral multiple ill-defined and hazy ground-glass-density areas 70 minutes after the traffic accident. (B) On the fourth hospital day, chest CT reveals the disappearance of the pulmonary lesions.

The edema without disruption of the alveoli can disappear within a few days [6]. This mechanism may explain the current case. However, the pulmonary lesions in this case appeared within 90 minutes of the impact, which is insufficient time to generate lung edema by systemic inflammatory reaction.

  1. Wintermark M, Duvoisin B, Schnyder P. Trauma of the pulmonary parenchyma. In: Wintermark M, Schnyder P, editors. Radiology of blunt trauma of the chest. New York: Springer; 2000. p. 57-69.
  2. Donnelly LF, Klosterman LA. Subpleural sparing: a CT finding of lung contusion in children. Radiology 1997;204:385-7.
  3. Raghavendran K, Davidson BA, Helinski JD, et al. A rat model for isolated bilateral lung contusion from blunt chest trauma. Anaesth Analg 2005;101:1482-9.
  4. Raghavendran K, Davidson BA, Woytash JA, et al. The evolution of isolated bilateral lung contusion from blunt chest trauma in rats: cellular and Cytokine responses. Shock 2005;24:132-8.
  5. Hoth JJ, Stitzel JD, Gayzik FS, et al. The pathogenesis of pulmonary contusion: an open chest model in the rat. J Trauma 2006;61:32-44.
  6. Rubin DM, McMillan CO, Helfaer MA, et al. Pulmonary edema associated with child abuse: case reports and review of the literature. Pediatrics 2001;108:769-75.
  7. West JB, Mathieu-Costello O. Stress-induced injury of pulmonary capillaries. Proc Assoc Am Physicians 1998;110:506-12.

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