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Evaluation of Pulmonary Embolism in Pediatric Patients with Nephrotic Syndrome with Dual Energy CT Pulmonary Angiography

Posted Feb 29, 2012 Updated Apr 10, 2023
By Long Jiang Zhang MD PhD , Zhen Jane Wang MD , Changsheng Zhou BS , Li Lu MS , Song Luo BS , Guang-Ming Lu
8 min read

Rationale and Objectives

The purposes of this study were to evaluate the prevalence of pulmonary embolism (PE) and renal vein thrombosis in pediatric patients with nephrotic syndrome using combined dual-energy (DE) computed tomographic (CT) pulmonary angiography (CTPA) and renal CT venography and to evaluate whether DE CTPA can improve the detection of PE in these children.

Materials and Methods

Thirty-two children (aged ≤ 18 years) were included in this study. All children underwent contrast-enhanced DE CTPA and renal CT venography; seven also underwent follow-up DE CTPA and renal CT venography. The presence of PE was determined by (1) CTPA derived from the average weighted 120-kVp images and (2) DE CTPA using dedicated DE software (syngo DE Lung PBV and syngo DE Lung Vessels), which can extract the iodine contents in lung parenchyma and pulmonary arteries. The prevalence and anatomic distribution of PE on CTPA from the average weighted 120-kVp images and DE CTPA and of renal vein thrombosis on CT venography were recorded by two radiologists in consensus; χ 2 tests were used to compare the difference in the detection rate of PE between DE CTPA and conventional CTPA.

Results

Of 32 children, nine (28.1%) had PE on the basis of the comprehensive DE CT pulmonary angiographic evaluation (CTPA from average weighted 120-kVp images and perfusion images and vascular images generated using the DE CT software). PE was localized in the lobar pulmonary artery in five patients (55.6%), the segmental pulmonary artery in six (66.7%), and the subsegmental pulmonary artery in five (55.6%). PE was distributed in the right upper lobe in two patients (22.2%), the right middle lobe in two (22.2%), the right lower lobe in five (55.6%), and the left lower lobe in six (66.7%). Compared to the CTPA derived from average weighted 120-kVp data, comprehensive DE CTPA showed solitary subsegmental PE in one additional patient (nine vs eight patients), one additional segmental (11 vs 10 segments), and four additional subsegmental pulmonary emboli (two vs six subsegmental pulmonary emboli) ( P > .05 for all). Eight children (25%) had renal vein thrombosis extending to the inferior vena cava ( n = 5).

Conclusions

The prevalence of PE was 28.1% and that of renal vein thrombosis 25.0% in the pediatric population with nephrotic syndrome on the basis of our small cohort. DE CTPA has the potential to improve the detection of PE in the pediatric population.

Pulmonary embolism (PE) is regarded as relatively rare in the pediatric population . Risk factors for pediatric PE include renal disease, especially nephrotic syndrome, because of altered levels of antithrombin and increases in other coagulation proteins . As in adults, PE is also difficult to diagnose clinically in the pediatric population, because of nonspecific symptoms. Echocardiography can be used to show clots within the heart and central pulmonary arteries and to evaluate pulmonary hypertension and right ventricular function, but it has low specificity and sensitivity for peripheral clots . Magnetic resonance imaging has been used for the diagnosis of PE in pediatric patients, without radiation dose, but magnetic resonance imaging has limited value for peripheral clots, and it is difficult to use magnetic resonance imaging in acutely ill patients. Multiple–detector row computed tomographic (CT) pulmonary angiography (CTPA), the reference standard for the diagnosis of PE in adults , was described as the study of choice for evaluating PE in children in one recently published survey .

To the best of our knowledge, the prevalence and anatomic distribution of PE on CTPA have rarely been reported in pediatric patients with nephropathy. Additionally, it was reported in several preliminary studies that the syngo DE Lung PBV and syngo DE Lung Vessels applications (Siemens Medical Solutions, Forchheim, Germany) for dual-energy (DE) computed tomography can be used for the detection of subsegmental pulmonary emboli. Lung PBV was shown to improve the detection of peripheral PE in experimental and clinical studies . Lung Vessels was developed to discriminate nonenhancing subsegmental pulmonary arteries from enhancing ones using DE iodine extraction data . Whether DE CTPA can provide additional diagnostic information for PE in nephrotic children is unclear. Therefore, the purposes of this study were to evaluate the prevalence of PE using DE CTPA and to evaluate whether DE CTPA can improve the detection of PE in a cohort of consecutive pediatric patients with nephrotic syndrome who were imaged with DE CTPA and renal CT venography.

Materials and methods

Study Subjects

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CT Imaging

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Image Postprocessing and Analysis

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Radiation Dose

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Statistical Analysis

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Results

Image Quality of DE CTPA

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Prevalence and Distribution of PE and Venous Thrombosis

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Figure 1, A 18-year-old female patient with chronic glomerulonephritis. Renal computed tomographic (CT) venography and conventional CT pulmonary angiography did not detect emboli in the renal veins and pulmonary arteries (not shown). Images from syngo DE Lung PBV (a–c) derived from dual-energy CT show typical triangular perfusion defects in the lateral segment of the right lower lung lobe ( arrow ). Images from syngo DE Lung Vessels (d–f) also show the subsegmental pulmonary artery, color coded red, in the right lower lung lobe ( arrow ).

Figure 2, A 9-year-old male patient with chronic nephrotitis. (a) Multiplanar reformatted (MPR) image shows a filling defect in the right renal vein extending into the inferior vena cava ( arrow ). (b) Oblique MPR image shows a filling defect in the right lower pulmonary artery ( arrow ), but no other emboli could be found in conventional computed tomographic pulmonary angiographic images from the average weighted 120-kVp data. (c) Axial, (d) coronal, and (e) sagittal images from syngo DE Lung PBV show triangular perfusion defects ( arrows ). (f) Image from syngo DE Lung Vessels shows the subsegmental pulmonary artery, color coded red, in the right lower pulmonary artery ( arrow ).

Figure 3, An 18-year-old male patient with membranous nephropathy. (a) Curved reformatted image shows a filling defect in the left renal vein extending into the orifice of the inferior vena cava ( arrow ). (b) Coronal multiplanar reformatted image shows the filling defect in the left lower pulmonary artery ( arrow ), but no other definitive filling defect was detected in conventional computed tomographic pulmonary angiographic images from the average weighted 120-kVp data. (c) Axial, (d) coronal, and (e) right sagittal images from syngo DE Lung PBV show a subsegmental perfusion defect in the right upper lobe ( solid arrow ) and a lobar perfusion defect in the left lower lobe ( open arrow ). (f) Axial, (g) coronal, and (h) right sagittal images from syngo DE Lung Vessels show subsegmental emboli in the right upper pulmonary artery ( solid arrow ) and lobar emboli in the left lower pulmonary artery ( open arrow ).

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Figure 4, A 16-year-old patient with podocytopathy. (a) Renal computed tomographic (CT) venography shows a filling defect in the right renal vein ( arrow ). (b) Conventional CT pulmonary angiography shows a filling defect in the right lower pulmonary arteries ( arrow ). Filling defects in the right upper and middle pulmonary arteries are not shown in this figure. (c) A sagittal image from syngo DE Lung PBV shows a lobar perfusion defect in the right middle and lower lung lobe and a segmental perfusion defect in the upper lung lobe ( arrows ). (d) Image from syngo DE Lung Vessels shows the segmental and lobar pulmonary arteries, color coded red, in the right middle lobe ( open arrow ) and in the lower lobe ( solid arrow ).

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Radiation Dose

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Discussion

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Conclusions

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Academic Radiology, Volume 19, Issue 3
Journals General Radiology
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