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ECR 2018 / C-0629
Are we over imaging the obese patient with suspected pulmonary embolus?
Congress: ECR 2018
Poster No.: C-0629
Type: Scientific Exhibit
Keywords: Emergency, Radioprotection / Radiation dose, Pulmonary vessels, CT-Angiography, Health policy and practice, Embolism / Thrombosis, Patterns of Care
Authors: M.-L. Gargan1, M. O'sullivan2, W. Torreggiani3; 1Dublin, N/A/IE, 2Dublin/IE, 3Dublin 24/IE


CT pulmonary angiography is the most sensitive test for diagnosis of pulmonary embolism and accounts for a significant proportion of the workload for any tertiary referral centre. Studies have shown that the diagnostic accuracy of CTPA in patients weighing 75-99kg or 100-150kg is not significantly different [4].                                                                                                                                

As the Irish population’s problem with obesity continues to rise, more requests for CTPAs will be placed due to the nonspecific signs and symptoms often present at baseline in the obese patient. Our audit has demonstrated that there is no significant difference in the proportion of positive studies between the obese and non-obese population, with 16% of positive studies demonstrated in the obese cohort and 15% of positive studies demonstrated in the non obese cohort.

This confirms that despite baseline symptoms of respiratory compromise being present in the obese population, it is a risk factor that contributes to pulmonary embolus along with other genetic and environmental factors, and that we are not over imaging the obese population, compared to the non obese population, as was initially suspected. 


However, in general, out of 221 patients, 186 (84%) were negative and 103 patients (46%) had a completely normal study with no significant findings. This indicates that we are over imaging patients in general with suspected pulmonary embolism and, whether obese or non-obese, exposing these patients to unnecessary radiation.


Understandably, sometimes this cannot be avoided as anxiety induced tachycardia in the emergency department and the wide range of GI, cardiac and musculoskeletal conditions that can cause pleuritic chest pain pose a diagnostic dilemma [5].

The non specific D dimer laboratory test often blurs the clinical picture, resulting in an increasing number of requests for CTPA due to raised D dimers. Our study proved its low specifity in the obese population, as 52 out of 59 patients who had a D dimer performed (88%) had a positive result, and only 11 of these had an acute pulmonary embolus (21%).          

With this in mind, careful physical examination and use of the Well’s score and PERC criteria should be strictly implemented to avoid a relatively high effective dose to young patients[6,7]. Furthermore, when appropriate, V/Q scanning should be performed as an alternative, especially in young women of child bearing age.  


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