Scintigraphic appearances in patients with pulmonary infection and lung scintigrams of intermediate or low probability for pulmonary embolism.

Out of 294 patients with lung scintigrams of low or intermediate probability for pulmonary embolism, the appearances in 54 patients with a final diagnosis of pulmonary infection were reviewed. The most common finding was a matched defect in ventilation and perfusion occurring in 40 patients (76%). Regional reverse mismatch occurred in 13 patients (24%) and both appearances were found in one patient (2%). Reverse mismatch was also present in a further seven patients, four of whom had bronchial obstruction. Although occurring less frequently than matched defects, 81% of regional reverse mismatched defects were because of chest infection. The presence of regional reverse mismatch in patients investigated for pulmonary embolism suggests the alternative diagnosis of chest infection.