Abstract

Aim: To quantify the incidence of unsuspected pulmonary emboli (PE) in an unselected in-patient population undergoing contrast enhanced multidetector CT (MDCT) thorax and to assess aetiological factors in their development.

Materials and Methods: All in-patients undergoing MDCT thorax over a ten month period were prospectively identified. Patients with previous or suspected current PE were excluded. CT scans were reviewed and the degree of contrast enhancement and presence of PE recorded. Where PE was found the level of most proximal thrombus was identified. Patient age, length of admission, slice scan thickness and clinical indication was noted.

Results: 547 in-patients having undergone MDCT were identified. Following exclusions 487 remained. 5.7% (28/487) demonstrated PE. Unsuspected PE was more common with increasing age (p<0.001), identified in 9.2% (20/218) of all patients over 70 years and 16.7% (11/66) of over 80 year olds. 64.3% were at segmental or sub- segmental level. No other aetiological factor was identified which significantly increased the incidence of unsuspected PE No significant difference was noted between 4- and 16-slice MDCT. 32.1% of incidental PE were not identified by the original reporting radiologists.

Conclusion: PE is an unsuspected finding on contrast enhanced MDCT thorax in 5.7% of all in- patients. This includes an incidence of 9.2% in patients > 70 years rising to 16.7% in over 80 years old. Most are peripheral and >30% are missed on initial review. PE should be routinely sought in all contrast enhanced MDCT of the chest irrespective of the indication for the CT scan.