A 27-year-old woman with a history of intravenous drug use was admitted to the hospital with complaints of fever, fatigue, and anorexia. An admission chest radiograph was performed (figure 1). A chest computed tomography (CT) scan was obtained to further define the lung disease (figure 2).
Prepared by Victoria Griffiths, MD and Charles White, MD
from the Department of Radiology at the University of Maryland
Medical Center, Baltimore, MD.
A 27-year-old woman with a history of intravenous drug use was
admitted to the hospital with complaints of fever, fatigue, and
anorexia. An admission chest radiograph was performed (figure 1). A
chest computed tomography (CT) scan was obtained to further define
the lung disease (figure 2).
Septic pulmonary emboli
The chest radiograph demonstrates multiple rounded parenchymal
nodules, several with central lucency suggesting cavitation (figure
1). There is no obvious pleural disease. The chest CT shows
multiple parenchymal nodules that occur in a vascular distribution
(figure 2). Some of these nodules demonstrate a feeding vessel;
some lesions are cavitary. Multiple pleural-based wedge-shaped
densities are noted that were not identified on the plain chest
Septic pulmonary emboli travel to the lungs from numerous
sources, including infected heart valves, peripheral sites of
septic thrombophlebitis, and infected indwelling venous catheters.
Other patients at risk are those with odontogenic infections.
In patients with a history of intravenous drug use, the most common
source of septic pulmonary emboli is an infected tricuspid valve.
An echocardiogram can be obtained to evaluate for the presence of
tricuspid valve vegetations. However, echocardiography may be
limited technically and very small vegetations (less than 3 to 4
mm) may not be detected.
Patients with septic pulmonary emboli who are diagnosed early
and treated with broad-spectrum antibiotics have a better prognosis
than patients with a delayed diagnosis. Establishing the diagnosis
of septic pulmonary emboli is not always straightforward, as the
radiographic findings may be non-specific. Blood cultures may be
negative initially and there may not be a detectable heart murmur.
Documented CT findings in septic pulmonary emboli include
multiple peripheral parenchymal nodules, a feeding vessel sign,
cavitation, and wedge-shaped peripheral lesions abutting the
This case demonstrates all of these findings. Additional CT
findings associated with septic pulmonary emboli include
air bronchograms within nodules, and extension into the pleural
When the chest radiograph is indeterminate, further evaluation with
CT can be extremely valuable as it may disclose unsuspected
pulmonary nodules and wedge-shaped subpleural densities.
The extent of disease documented by CT is generally greater than
that detected by radiography. There have been patients with
negative chest radiographs in whom subsequent CT examination
confirmed septic pulmonary emboli.
The diagnosis of septic pulmonary emboli is made on the basis of
characteristic imaging abnormalities in association with one or
more of the following criteria: positive blood cultures, tricuspid
valve vegetations proven by echocardiography, a clinical course
compatible with bacterial endocarditis (a new murmur which resolves
after treatment), or other signs of septic embolization
(splenomegaly, petechiae, or both).
In this case, the patient had
bacteremia and a heart murmur.
Chest radiography remains the screening test of choice for
septic pulmonary emboli.
Not every patient with suspicion of septic pulmonary emboli
requires CT evaluation. However, studies have shown that the
pattern of parenchymal involvement in septic pulmonary emboli is
more recognizable and specific by CT than by radiography.