Imaging of suspected pulmonary embolism and deep venous thrombosis in obese patients

Abstract

Obesity is a growing problem around the world, and radiology departments frequently encounter difficulties related to large patient size. Diagnosis and management of suspected venous thromboembolism, in particular deep venous thrombosis (DVT) and pulmonary embolism (PE), are challenging even in some lean patients, and can become even more complicated in the setting of obesity. Many obstacles must be overcome to obtain imaging examinations in obese patients with suspected PE and/or DVT, and to ensure that these examinations are of sufficient quality to diagnose or exclude thromboembolic disease, or to establish an alternative diagnosis. Equipment limitations and technical issues both need to be acknowledged and addressed. Table weight limits and scanner sizes that readily accommodate obese and even morbidly obese patients are not in place at many clinical sites. There are also issues with image quality, which can be substantially compromised. We discuss current understanding of the effects of patient size on imaging in general and, more specifically, on the imaging modalities used for the diagnosis and treatment of DVT and PE. Emphasis will be placed on the technical parameters and protocol nuances, including contrast dosing, which are necessary to refine and optimize images for the diagnosis of DVT and PE in obese patients, while remaining cognizant of radiation exposure. More research is necessary to develop consistent high-level evidence regarding protocols to guide radiologists, and to help them effectively utilize emerging technology.

Figure 1.

CT pulmonary angiography in a 15-year-old boy with a BMI of 50. Although the patient is obese, and there is truncation artifact on the left side, the examination is diagnostic for saddle PE (arrows in a, b) and associated right heart strain (c). BMI, body mass index; PE, pulmonary embolism.

Figure 2.

CT pulmonary angiography in a 46-year-old male with a BMI of 86. The examination shows dilated central pulmonary arteries (a), mild cardiomegaly (b) and no obvious central embolus. The examination is extremely limited secondary to the patient’s body habitus and poor i.v. contrast opacification. BMI, body mass index.

Figure 3.

CT pulmonary angiography in a 39-year-old female with a BMI of 40. An initial scan with a kVp of 100 (a) shows a questionable PE (arrow). Repeat scan with a kVp of 120 (b) shows that this was an artifact. BMI, body mass index; .

Figure 4.

CT pulmonary angiography in a 17-year-old boy with dyspnea and possible PE. An initial scan with 1 mm thick images (a) shows excessive noise. A repeat scan with 3 mm thick images (b) shows reduced noise.

Figure 5.

CTPA in a 34-year-old male with a BMI of 75. Initial evaluation (a) was markedly limited due to infiltration of i.v. access and the patient's large body habitus. This was a non-diagnostic examination for PE. A new i.v. was placed, and subsequent repeat CTPA (b−d) demonstrated extensive bilateral PE (arrows) with a saddle component, and associated right heart strain. BMI, body mass index; CTPA, CT pulmonary angiography; PE, pulmonary embolism.

Figure 6.

Lower extremity ultrasound in a 73-year-old female with a BMI of 63.5. Non-compression (a) and compression (b) views of the right femoral and deep femoral vein shows probable thrombus of the right common femoral vein. Subsequent CTV (c) of the same patient, performed after sonography, confirms right upper thigh DVT (arrow). BMI, body mass index; CTV, CT venography; DVT, deep venous thrombosis.

Figure 7.

Lower extremity ultrasound in a 64-year-old female with a BMI of 51. Non-compression (a) and compression (b) views of the right superficial femoral vein (arrows). No obvious acute DVT is appreciated, although these vessels are partially obscured by overlying tissues. The examination must be considered inconclusive at this level for determining the presence or absence of lower extremity DVT. BMI, body mass index; DVT, deep venous thrombosis.

Figure 8.

Ultrasound in a 30-year-old male with a BMI of 68.7. Non-compression longitudinal image of the right femoral vein (a) shows limited visualization of the vein due to overlying soft tissue. The vein is identified by Doppler imaging (b) at a depth of 7 cm. No DVT was identified. Subsequent CTPA shows an embolus in the right lower lobe pulmonary artery (arrow in c), mild cardiomegaly (c) and contrast-blood mixing artifact in the left heart (arrow in d). BMI, body mass index; CTPA, CT pulmonary angiography; DVT, deep venous thrombosis.

Figure 9.

Lung V/Q scan in a 26-year-old male with a BMI of 83. Planar ventilation images of the lungs were obtained in the anterior (a), right anterior oblique (b) and left anterior oblique projections. Corresponding planar perfusion images of the lungs were obtained in the anterior (d), right anterior oblique (e) and left anterior oblique (f) projections. Posterior views of the lungs could not be obtained due to the patient's body habitus. Dedicated gamma camera imaging table for the lung scan could not be utilized, and lung images were only obtained in the anterior views while the patient was in a supine position on his hospital stretcher. Paired ventilation images demonstrate matched ventilation defects, which are larger than the perfusion defects. There are no segmental or subsegmental mismatched perfusion and ventilation abnormalities to suggest pulmonary embolism in the visualized anterior view. BMI, body mass index; V/Q scan, ventilation-perfusion scan.