Case Author(s): Scott Winner, M.D. and Jerold Wallis, M.D. , 9/27/96 . Rating: #D2, #Q3

Diagnosis: Pulmonary Embolism

Brief history:

41-year old woman with shortness of breath.

Images:

Perfusion images of the lungs

View main image(vq) in a separate image viewer

View second image(vq). Ventilation images of the lungs

View third image(ct). CT of the chest

The chest radiograph (not shown) was without infiltrates or effusions.

Full history/Diagnosis is available below

Diagnosis: Pulmonary Embolism

Full history:

41-year old woman with history of metastatic breast cancer, increased shortness of breath, and decreased 02 saturation.

Radiopharmaceutical:

4.3 mCi Tc-99m MAA iv and 19.7 mCi Xe-133 gas by inhalation

Findings:

Decreased perfusion is seen to the right lung (particularly evident in the right lower lobe on the RPO image) and (after allowing for the heart) a moderate segmental defect in the anterior portion of the left lower lobe (best seen on the left lateral image). In the absence of significant ventilation or radiographic abnormalities, this yields a high likelihood ratio for pulmonary embolism.

CT findings are discussed in the "followup" section below.

Discussion:

Isolated lobar or whole lung decreased perfusion is relatively atypical in pulmonary embolism, and should raise the suspicion of other central obstructing lesions (e.g. hilar tumor mass, fibrosing mediastinitis). In this case, an additional defect is present in the contralateral lung to increase the suspicion for pulmonary embolism.

Computed tomography may be the confirmatory test of choice in this setting, since it can both evaluate for hilar mass and detect central obstructing clot.

References: Remy-Jardin M, et al., Diagnosis of Pulmonary Embolus with Spiral CT: Comparison with Pulmonary Angiography and Scintigraphy. Radiology 1996; 200:699-706.

Followup:

CT scan of the chest dated 8- 31-96 showed a large central pulmonary embolus in the right interlobar pulmonary artery with additional filling defects seen in the left lower lobe pulmonary artery consistent with pulmonary embolism.

Major teaching point(s):

When a perfusion abnormality involves an entire lung or lobe, one should consider other etiologies for the perfusion defect. This is a somewhat unusual presentation for pulmonary emboli.

Differential Diagnosis List

Central tumor obstructing the pulmonary artery, mediastinal fibrosis, vascular anomaly (pediatric patients) and large central pulmonary embolus.

ACR Codes and Keywords:

References and General Discussion of Ventilation Perfusion Scintigraphy (Anatomic field:Lung, Mediastinum, and Pleura, Category:Organ specific)

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Case number: vq019

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