Radiological Investigation of Pulmonary Embolism: an Audit in a Teaching Hospital

VWK Au, E Veitch, S Gustafson, F Kermeen, MR Sage

Hong Kong J Radiol 2005;8:141-5

Objective: Since the introduction of computed tomography pulmonary angiography, radiological investigation of pulmonary embolism has been revolutionised. Escalating numbers of computed tomography pulmonary angiography have been performed in the past 5 years in our institution. The purpose of this study was to audit the use of radiologic investigations in the assessment of patients with suspected pulmonary embolism.

Patients and Methods: A retrospective study was performed during a 3-month period in 2002. All patients who underwent computed tomography pulmonary angiography or ventilation-perfusion lung scan or both for suspected pulmonary embolism were approached for inclusion in the study.

Results: Of the 145 patients consented to the study, 92 (63%) had computed tomography pulmonary angiography with 12 (13%) being positive for pulmonary embolism. Fifty nine (41%) had ventilation-perfusion lung scan, of which 6 (10%) had a high probability scan. Only 6 patients underwent both investigations. There was a very low rate of intermediate probability ventilation-perfusion lung scans, occurring in only 6 cases (10%). Duplex ultrasound scan of the lower limbs was performed in 27 patients (19%), with deep vein thrombosis being detected in 8 patients. The only statistically significant risk factor for pulmonary embolism was underlying malignancy (p < 0.01). Patients referred for computed tomography pulmonary angiography were significantly older, more likely to have an abnormal chest X-ray and more likely to have underlying respiratory disease than those referred for ventilation-perfusion lung scan (p < 0.005 for all 3 parameters). Ancillary findings on computed tomography pulmonary angiography were reported in 74 (80%) patients.

Conclusions: Although patients were appropriately streamed to computed tomography pulmonary angiography versus ventilation-perfusion lung scan, the relatively low prevalence of pulmonary embolism in our audit indicates poor patient selection, and consequently an over-utilisation of these investigations.