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SARS: Imaging of Severe Acute Respiratory Syndrome

¹ All authors: Department of Radiology, Vancouver General Hospital, University of British Columbia, 899 W. 12th Ave., Vancouver, B. C., V5Z 1M9, Canada.

Received March 26, 2003; accepted after revision March 28, 2003.

 
Address correspondence to S. Nicolaou (snicolao{at}vanhosp.bc.ca).

Introduction

Top Introduction Case Report Discussion References

 
Severe acute respiratory syndrome (SARS) is an atypical pneumonia that has recently been reported in Asia, North America, and Europe. More than 2671 patients have been affected, and 103 have died [1].

As part of an effort to facilitate early diagnosis, we report the radiographic and CT findings in one patient with SARS.

Case Report

Top Introduction Case Report Discussion References

 
A 55-year-old previously healthy man who had recently traveled to Hong Kong presented with a 2-week history of fever, headache, malaise, dyspnea, and a slightly productive cough. The patient was a nonsmoker with no known risk factors. At physical examination, he had a fever of 101.3°F (38.5°C) and decreased air entry to both lower lobes on auscultation. Oxygen saturation level for room air was 45% (normal level, > 95%). Laboratory results revealed an increased WBC (14.2 x 10⁹/L; normal range, 4.0-11.0 x 10⁹/L) with neutrophilia (13.7 x 10⁹/L; normal range, 2.0-8.0 x 10⁹/L). Lymphocytes were low (0.6 x 10⁹/L; normal range, 1.2-3 x 10⁹/L). Eosinophils were normal (0.0; normal range, 0-0.7 x 10⁹/L). Creatinine (151 µmol/L; normal range, 60-115 µmol/L) and urea (16.8 mmol/L; normal range, 1.8-8.2 mmol/L) levels were elevated, indicating renal insufficiency. The patient was anemic (hemoglobin level, 84 g/L; normal range, 135-175 g/L). Bedside anteroposterior computed radiography (Fig. 1A) performed with the patient in an upright position revealed diffuse bilateral ground-glass opacification with poorly defined nodules and mild air-space consolidation in the retrocardiac region of the right lower lobe. Mild cardiomegaly was noted.

View larger version (146K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1A. —55-year-old previously healthy man with history of recent travel to Hong Kong. Bedside anteroposterior computed radiograph obtained with patient upright shows extensive bilateral ground-glass opacities and poorly defined nodular pattern. Abnormalities are diffuse in right lung, but radiograph shows relative sparing of left lung apex. Mild air-space consolidation is seen in retrocardiac region of right lower lobe. Note mild cardiomegaly.

The patient was admitted to the intensive care unit with a diagnosis of atypical pneumonia. Twelve hours after admission, the patient's condition worsened, and he was treated with intubation. A computed chest radiograph (Fig. 1B) obtained after intubation revealed diffuse bilateral air-space consolidation. Further questioning of the family revealed that the patient was exposed to other individuals recently diagnosed with SARS in Hong Kong; therefore, the diagnosis of SARS was made.

View larger version (132K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1B. —55-year-old previously healthy man with history of recent travel to Hong Kong. Bedside anteroposterior computed radiograph obtained with patient supine 12 hr after initial radiograph (A) shows diffuse bilateral air-space consolidation. Note prominent air bronchograms, low position of endotracheal tube, and gaseous distention of stomach. Radiographic findings and rapid progression are consistent with adult respiratory distress syndrome.

The following day, a chest CT scan was obtained using a multidetector four-track CT scanner (LightSpeed QX/i, General Electric Medical Systems, Milwaukee, WI) (Fig. 1C) (5-mm collimation, 0.8 sec per rotation, 11.25-mm table feed, 120 kV, 181 mA; lung window and level settings, 1500 and 700 H, respectively; mediastinal window and level settings, 350 and 35 H, respectively). Images were reviewed on a PACS (picture archiving and communication system) monitor (IMPAX, version 4.1, Service Pack 4.0, Agfa, Toronto, Ontario). The examination was performed without administration of contrast agent because of the patient's renal insufficiency. The chest CT scans showed extensive bilateral areas of ground-glass attenuation and dependent areas of consolidation in both lower lobes. The CT findings were interpreted as consistent with adult respiratory distress syndrome. Findings of bronchoalveolar lavage were negative for malignancy and viral inclusion bodies; initial Ziehl-Neelsen stains were negative for acid-fast bacilli. Silver stains were negative for Pneumocystis carinii pneumonia. The bronchoalveolar lavage specimen showed mixed acute and chronic inflammatory cells and large numbers of lymphocytes. Findings of Gram stains and Legionella and blood cultures were also negative. Tracheal aspirates were sent to the Canadian Centre for Disease Control (Winnipeg, Manitoba), and results were negative. The patient is still being treated with mechanical ventilation but has improved slightly 4 weeks after admission.

View larger version (107K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1C. —55-year-old previously healthy man with history of recent travel to Hong Kong. Transverse unenhanced image obtained on multidetector four-track CT scanner (LightSpeed QX/i, General Electric Medical Systems, Milwaukee, WI) at level of apical segments of upper lobes shows extensive bilateral areas of ground-glass attenuation, more severe on right, and focal areas of consolidation in right upper lobe. Note lobular areas of sparing particularly in left upper lobe.

Discussion

Top Introduction Case Report Discussion References

 
SARS is a new form of potentially fatal pneumonia. The illness usually begins with a fever greater than 100.4°F (38°C), often associated with chills or other symptoms including headache, malaise, and body aches. A dry nonproductive cough usually develops. Patients typically deteriorate over the following 48-72 hr. Approximately 10-20% of patients require mechanical ventilation [2].

The exact cause of SARS is not known. Recent reports from Germany, Hong Kong, and Canada suggest that SARS may be caused by an infectious agent, Metapneumovirus, part of the paramyxovirus family, which includes viruses responsible for mumps, measles, and respiratory infections, particularly in children. The paramyxovirus family also includes more rare and recently recognized viruses such as the Hendra and Nipah viruses, which caused a disease outbreak in Malaysia several years ago [2]. However, recent reports from the United States and Canadian Centers for Disease Control and Prevention have identified a common cold virus known as Coronavirus from the tissue of two infected patients [2]. Different types of viruses cause colds, including three different types of the Coronavirus. The Centers for Disease Control and Prevention currently believes that the type of Coronavirus responsible for SARS is genetically different and most likely represents a fourth lethal type.

The Centers for Disease Control and Prevention recommends that patients with SARS receive the same treatment as that used for any patient with a serious community-acquired atypical pneumonia of unknown cause. Treatment regimens have included supportive treatment and antibiotics in hope of treating known bacterial agents causing atypical pneumonias. Therapy has also included antiviral agents such as ribavirin and oseltamivar in combination with steroids and antibodies found in the serum of recovered patients [3].

Initial imaging features on chest radiographs include unilateral or bilateral patchy or confluent areas of air-space consolidation or ground-glass opacities. Small effusions may be present initially [4]. In our patient, the initial findings of extensive bilateral ground-glass opacification with a poorly defined nodular pattern likely reflected early findings of acute respiratory distress syndrome, which rapidly progressed to extensive bilateral air-space consolidation. The radiographic findings, rapid progression, and CT features of diffuse ground-glass attenuation and air-space consolidation are consistent with acute respiratory distress syndrome.

In summary, the imaging features of SARS are nonspecific and can range from consolidation in a lobar or nonlobar distribution to extensive ground-glass opacities and air-space consolidation characteristic of acute respiratory distress syndrome.

View larger version (110K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1D. —55-year-old previously healthy man with history of recent travel to Hong Kong. CT image obtained at level of right upper lobe bronchus shows diffuse bilateral areas of ground-glass attenuation and dependent areas of consolidation.

View larger version (123K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1E. —55-year-old previously healthy man with history of recent travel to Hong Kong. CT image obtained at level of lower lobe bronchi shows findings similar to those in B.

View larger version (104K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1F. —55-year-old previously healthy man with history of recent travel to Hong Kong. CT image obtained at mediastinal window settings (width and level, 350 and 35 H, respectively) shows dependent consolidation and small bilateral pleural effusions. Note presence of air bronchograms.

References

Top Introduction Case Report Discussion References

 

1. World Health Organization Web site. Available at: www.who.int/csr/sarscountry. Accessed April 1, 2003
2. Centers for Disease Control and Prevention Web site. Available at: www.cdc.gov/ncidod/sars/faq.htm. Accessed April 1, 2003
3. World Health Organization Web site. Available at: www.who.int/csr/sars/clinical/en/. Accessed April 1, 2003
4. CUHK Department of Diagnostic Radiology & Organ Imaging Web site. Available at: www.droid.cuhk.edu.hk/web/default.htm. Accessed April 1, 2003

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