NONEMBOLI HIGH-PROBABILITY PERFUSION LUNG-SCAN FOR PULMONARY THROMBOEMBOLISM

Pulmonary thromboembolism (PTE) is a disease whose diagnosis in the em ergency department constitutes a challenge to the clinician. Perfusion lung scans have been important in helping in this context, mainly bec ause of the fact that a normal perfusion lung scan rules out the prese nce of a clinically significant PTE. Nevertheless, false-positive resu lts are sometimes observed, causing a diagnostic dilemma. An example i s a case of bronchogenic carcinoma involving a pulmonary artery or its branches. In such patients, some characteristics of the scintigraphic imaging could guide the diagnosis toward a nonembolic origin of the p erfusion defect. A case of small-cell carcinoma of the lung involving the left pulmonary artery whose clinical presentation suggested consid ering the possibility of PTE is reported. The so-called ''stripe sign' ' is reviewed, and certain clues for the differential diagnosis of a m assive and one-sided perfusion defect are discussed.