AJR 2001; 176:712
© American Roentgen Ray Society
Radiologic-Pathologic Conferences of the
MetroWest Medical Center,
Framingham, Massachusetts |
Unilateral Absence of Pulmonary Perfusion Mimicking Pulmonary Embolism
Bernard Chow1,2,
Conrad Wittram3 and
Victor W. Lee4
1
Department of Radiology, MetroWest Medical Center, Framingham Union Hospital,
Framingham, MA 01701.
2
Present address: Department of Radiology, Brigham and Women's Hospital,
Harvard Medical School, 75 Francis St., Boston, MA 02115.
3
Department of Radiology, Massachusetts General Hospital, Harvard Medical
School, 55 Fruit St., Boston, MA 02114.
4
Department of Radiology, Boston Medical Center, Boston University, 88 E.
Newton St., Boston, MA 02118.
Received June 12, 2000;
accepted after revision September 25, 2000.
Address correspondence to B. Chow.
Introduction
A finding of unilateral absence of pulmonary perfusion on a
ventilation-perfusion (V/Q) scan is associated with many congenital,
inflammatory, infectious, and neoplastic processes. When abnormalities are
detected on a scan, the diagnosis of pulmonary embolism should be considered.
However, another cause is more likely. In this patient, a finding of
uni-lateral nonperfusion illustrated a pulmonary artery sarcoma mimicking
acute pulmonary embolism.
A 69-year-old woman presented with sudden onset of pleuritic chest pain and
dyspnea. She was tachycardic, and the results of an arterial blood-gas test
showed mild hypoxemia. A chest radiograph showed a slight prominence of the
left hilum and a small left pleural effusion. A V/Q scan
(Fig. 1A) showed a virtual
absence of left lung perfusion when the lungs were normally ventilated. A
diagnosis of massive pulmonary embolus was made, and immediate tissue
plasminogen activator thrombolysis was performed. The patient showed no
clinical improvement. Subsequent CT with IV contrast material
(Fig. 1B) showed a mass filling
the pulmonary trunk and left pulmonary artery, a finding confirmed by
pulmonary arteriography (Fig.
1C). MR imaging with gadolinium showed heterogeneous enhancement
in the lobulated mass. An endovascular biopsy sample was obtained, and a left
pneumonectomy and pulmonary artery resection with graft replacement were
performed. The final pathologic diagnosis was malignant fibrous histiocytoma
(Figs. 1D and
1E).
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Fig. 1A. —69-year-old woman with pleuritic chest pain and dyspnea.
Composite image from posterior projection of ventilation-perfusion scan was
obtained with technetium-99m diethylenetriamine pentaacetic acid aerosol
(left) and technetium-99m macroaggregated albumin (right).
Absence of left pulmonary perfusion is noted when lungs are normally
ventilated.
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Primary tumors of the pulmonary artery are rare entities. As of 1997, only
138 cases had been reported in the literature
[1]. The most common signs and
symptons reported are dyspnea (76%), chest pain (60%), cough (53%), systolic
murmur (51%), and hemoptysis (29%)
[1]. Although pulmonary artery
neoplasm can cause unilateral nonperfusion, in rare cases it can mimic acute
pulmonary embolism [2]. In this
patient, the clinical presentation and abnormalities in the V/Q scan suggested
the diagnosis of pulmonary embolism. In cases in which there is an absence of
a chronic presentation, weight loss, or evidence of distant metastases, the
diagnosis is notoriously difficult, with 60% of cases diagnosed at autopsy and
the rest diagnosed at the time of surgery
[1]. Because of the high
surgical mortality and poor prognosis for treatment of the tumor itself, it is
important that the diagnosis be made without resorting to surgery. Contrast
enhancement on MR imaging, transthoracic needle biopsy, and endovascular
catheter biopsy have all been successful
[3]. In retrospect, we could
see that the CT scan showed the pulmonary artery-filling defect with subtle
enhancement, indicating that it was likely neoplasm and not pulmonary
embolus.
Unilateral absence of perfusion is a rare and dramatic finding of V/Q
scans. In one reported series, this finding was observed in only 13 (2.1%) of
607 V/Q scans obtained over the course of 1 year
[4]. Three (23%) of the 13
cases of unilateral nonperfusion were due to pulmonary embolism; the remaining
10 cases (76%) were due to miscellaneous causes
[4]. These miscellaneous causes
can be subdivided into neoplastic, inflammatory, infectious, and congenital
causes. Cases of bronchogenic carcinoma, mucous plug, cyst, or adenoma;
extrinsic lesions such as thoracic aortic aneurysm or dissection; and rare
causes such as congenital absence of pulmonary artery, histoplasma
mediastinitis, and Swyer-James syndrome have all been reported
[2,4].
These findings suggest that unilateral non-perfusion is more likely to be
caused by something other than acute pulmonary embolus.
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Introduction
References
