Comparison of Colour Doppler Ultrasonography and Indirect Computer Tomography Venography for the Diagnosis of Deep Venous Thrombosis in Patients with Suspected Pulmonary Thromboembolism at a Tertiary Care Centre in Chennai, Tamil Nadu, India
Correspondence Address :
Dr. Pon Shankar Anandaraja,
Assistant Professor, Department of Radiodiagnosis, Government Stanley Medical College and Hospital, Old Jail Road, Old Washer Menpet, Chennai, Tamil Nadu, India.
E-mail: ponshankara@gmail.com
Introduction: Pulmonary Thromboembolism (PTE) and Venous Thromboembolism (VTE) are prevalent conditions with a high mortality rate and need immediate medical attention. The initial and standard imaging techniques are Computed Tomography Pulmonary Angiography (CTPA) for the diagnosis of PTE and Colour Doppler Ultrasonography (CDUS) for Deep Vein Thrombosis (DVT). However, there can be some issues when using these two different approaches, like the requirement for a separate area and more time. With the so-called indirect Computed Tomography Venography (CTV) approach, thrombi in the deep venous system that may cause PTE can be examined right after pulmonary CT Angiography (CTA) without the need for additional contrast agent.
Aim: To determine the accuracy of indirect CTV for the diagnosis of deep venous thrombosis in patients with suspected PTE.
Materials and Methods: This cross-sectional study was conducted in the Department of Radiology in Government Stanley Medical College, Chennai, Tamil Nadu, India, India from June 2021 to May 2022. A total of 50 patients with a probable diagnosis of PTE and was established with CTA were included. All 50 patients underwent indirect CTV and CDU on the same day. For indirect CTV lower extremities between the iliac crest and the popliteal region were scanned without administration of extra contrast medium. Colour Doppler Ultrasound (CDUS) was considered as Gold standard. To find the efficacy of CTV in determining DVT the Receiver Operating Characteristics curve (ROC) was used.
Results: Of the total 50 patients, who were enrolled in the study, 21 (42%) patients were females and 29 (58%) patients were males. The mean age of the study subjects was 43.5±12.1 years. Among these DVT was detected in 25/50 patients (50.0%) by Doppler Sonography, Similarly DVT was detected in 23/50 patients (46%) by CTV. The sensitivity of CTV was 76% and the specificity was 84%, Positive Predictive Value (PPV) of 82.6%, Negative Predictive Values (NPV) of 77.8%. The p-value and kappa value between CTV and CDUS was calculated as 0.0005 and 0.600, respectively.
Conclusion: According to the results of the present study, a combined CTA indirect CTV method can determine the DVT with a moderate level of sensitivity and specificity.
Contrast media, Lower limb, Pulmonary artery
The PTE and VTE are common conditions that are fatal and require urgent treatment (1). It is the common emergency seen after surgery, childbirth, prolonged bed rest, and trauma (2). The likelihood of pulmonary embolism is evaluated by clinical prognosis and laboratory studies. Utilising imaging tools, a definitive diagnosis is frequently made (3). DVT is the primary aetiology of PTE in 90% of patients (4). PTE and DVT, two distinct thromboembolism components, are diagnosed using various techniques. Today, among these techniques, CDUS for the detection of DVT and CTPA for the diagnosis of PTE has emerged as the first fundamental imaging modalities (5),(6). However, applying these two different methods separately can lead to the following problems: Need for extra space and time, difficulty in moving the patient, delay in diagnosis, and failure to use CDUS effectively in some patients.
Recently, in patients undergoing CTA for PTE, venous structures below the level of iliac crest have been assessed with CT venography sections obtained after a given waiting period, based on the assumption that adequate opacification would be attained without administration of additional contrast medium (6),(7).
The aim of the present study was to determine the accuracy of indirect CTV for the diagnosis of deep venous thrombosis in patients with suspected PTE.
This cross-sectional study was conducted in the Department of Radiology in Government Stanley Medical College Chennai, Tamil Nadu, India from June 2021 to May 2022 after obtaining Ethical Committee clearance (20210692).
Inclusion and Exclusion criteria: Patients with a presumptive diagnosis of pulmonary embolism which was confirmed by CT pulmonary angiogram were included in the present study. Patients who have contrast hypersensitivity, all pregnant patients, children less than 18 years, patients with renal failure, and those patients who are not willing to give consent to the study.
Sample size calculation: The sample size was calculated based on a previous study by Nayman A and Odev K in which sensitivity to determine PE was 81.8% with indirect CTV of the leg (8).
Study Procedure
The CTA and CTV were performed using a multislice CT with 128 detectors (GE-Optima 660). An 18-20 Gauge catheter was used to provide vascular access before the procedure in the antecubital vein. The patient was positioned properly to allow for a full examination of the lower extremities. An autoinjector was used to administer 60 mL of non ionic contrast at a rate of 3 mL/sec through the antecubital vein. Prior to and following the administration of the contrast medium, automated injectors were used to administer 10 mL and 20 mL of isotonic saline, respectively.
In order to prevent breathing artifacts, the patients were instructed to hold their breath throughout the examination. The investigation was performed at the supine position with hands over head level to avoid artifacts. From the lung apex to the diaphragm, CTPA was done. Then, reconstruction images with 1 mm section thicknesses were created. Vascular structures were assessed using images with a 1 mm slice thickness. Images with a 1 mm section thickness were used to assess the pulmonary parenchymal structures. From the iliac crests to the popliteal fossa, indirect CTV was carried out. Indirect CTV was performed three minutes after contrast was administered, without the use of any extra contrast. With a slice thickness of 2 mm, CTV images were obtained craniocaudally. The evaluation of PTE and DVT was done using pulmonary CTA and CTV images, respectively. Utilising density measurements in the main femoral vein, it was determined whether the level of venous opacification was optimum. Opacification of atleast 70 HU was considered adequate.
Doppler ultrasonography was performed for all patients on the same day (Mindray DC-60). Patients in the supine position using high-frequency linear probe lower limb veins were first examined with B-mode (brightness mode) gray-scale sonography in transverse, and longitudinal views followed by CDUS examination in which the direction of flow, filling of the vessel can be assessed and spectral doppler wave form was obtained from small interrogation region (sample volume) in the vessel of the target, which gives characteristic waveform and velocity of flow of the target vessels.
For each examined vessel, the following were determined:
1) Presence or absence of the vessel image on real-time imaging;
2) Compressibility of the vessel;
3) Presence or absence of intraluminal echogenic material;
4) Presence or absence of a flow (Doppler signal) within the vessel.
Diagnostic Criteria
The presence of hypodense filling defect in the pulmonary artery and its branches, was accepted as direct diagnostic criteria for pulmonary embolism. Auxillary diagnostic criteria were peripheral wedge of airspace opacity, mosaic attenuation, and enlarged pulmonary artery. According to these criteria, the presence and location of pulmonary embolism was made. Similarly analysis of CTV was made, observation of a hypodense filled defect within the vein on consecutive CTV slices was accepted as a direct diagnostic criterion for DVT. Auxiliary diagnostic criteria were venous widening, infiltration/fat stranding in the perivenous fat tissue. In the study, CDUS was accepted as the gold standard.
Statistical Analysis
The collected data were analysed with IBM Statistical Package for the Social Sciences (SPSS) for Windows, version 23.0. (Armonk, NY: IBM Corp). To describe about the data descriptive statistics frequency analysis, percentage analysis were used for categorical variables and the mean and Standard Deviation (SD) were used for continuous variables. Sensitivity, Specificity, PPV and NPV and accuracy, and Cohen kappa was used to find the agreement. In all the above statistical tools the probability value of 0.05 was considered as significant.
Of the total 50 patients, who were enrolled in the study, 21 patients were females and 29 patients were males. The mean age of the study subjects was 43.5±12.1 years and the age distribution is summarised in the (Table/Fig 1).
Co-morbidities were present in 22 patients, hypertensive (n=6), diabetic (n=10), Tuberculosis (TB) (n=2), Chronic Obstructive Pulmonary Disease (COPD) (n=4). The signs and symptoms of DVT were present in 26/50 patients (52.0%), and previous history of DVT was present in six patients. Right pulmonary artery, partial thrombus has the highest percentage (18.0%), and left pulmonary subsegmental arteries, partial thrombus has the lowest percentage (2.0%) (Table/Fig 2).
The DVT was detected in 25/50 patients (50.0%) by doppler sonography, Similarly DVT was detected in 23/50 patients (46%) by CTV. Pathologies other than pulmonary embolism like COPD, inguinal hernia, and TB cardiomegaly were also detected In CTA and indirect CTV (Table/Fig 3).
The ROC curve shows the area of the curve was 0.800, p-value=0.0005 with 95% CI 0.671 to 0.929 (Table/Fig 4),(Table/Fig 5).
The sensitivity was 76%, specificity was 84%, PPV was 82.6%, NPV was 77.8% and diagnostic accuracy of 80.0%, p-value and kappa value between CTV and CDUS were calculated as 0.0005 and 0.600, respectively (Table/Fig 6).
In one of the case, pulmonary embolism was present right and left pulmonary arteries causing partial obstruction (Table/Fig 7)a. DVT was detected through indirect CTV in the right femoral vein and popliteal veins (Table/Fig 7)b,c, venous opacification degree was +84 HU (Table/Fig 7)d, the findings found in CTV was confirmed by doppler sonography (Table/Fig 7)e,f.
Venous thromboembolic disease is common disorders that contribute significantly to morbidity and mortality. The Prospective Investigation of Pulmonary Embolism Diagnosis II (PIOPED II) investigators (1) recommend that, clinical assessment should be performed before imaging and with an objective method. Most PIOPED II investigators recommend CTA and CTV for patients with a high probability of PE based on clinical assessment (1).
In a study by Duwe KM et al., 74 patients underwent indirect CTV with CT pulmonary angiography and used lower extremity venous ultrasonography as standard (9). In their study, CTV had a specificity of 94%, sensitivity of 89%, a NPV of 98% and PPV of 64%. Loud PA et al., performed indirect CTV after CT pulmonary angiography and used lower extremity venous sonography as the standard (10). In that study, the sensitivity and specificity of CTV were 97% and 100%, respectively, for the evaluation of femoropopliteal DVT. Loud PA et al., also found 17% of DVT in the pelvic or abdominal veins could not be imaged by sonography (10). In a study by Baldt MM et al., compared CTV with conventional venography as a standard (11). In this study, CTV for DVT analysis found a sensitivity of 100%, a specificity of 96%, a PPV of 91%, and a NPV of 100%.
In a study by Karaoglu O et al., Pulmonary embolism was determined in a total of 19 patients out of 80 patients (12). Six patients had DVT on CTV examination, even though the CDUS findings were normal. CDUS findings were considered as the gold standard, the sensitivity of CTV in determining DVT was found to be 100%, specificity 91%, PPV 60%, NPV 100%. In study by Taffoni MJ et al., indirect CTV, along with CT pulmonary angiography, was performed in 61 symptomatic ICU patients, with lower extremity duplex venous sonography performed within 24 hours (4). CTV and sonography were compared with an outcome standard. The sensitivity and specificity of CTV were 70% and 96%, respectively, with a PPV of 77% and a NPV of 94%.
In a study by Garcia-Bolado A and Del Cura JL, they compared the diagnostic value of the indirect CTV vs Doppler ultrasound, the current “gold standard” for the diagnosis of DVT in patients, in which DVT was the primary consideration (13). In this comparison, they obtained specificity 95.0%, NPV 93.2%, sensitivity 58.8% and PPV 66.7%.
The present study and the prior literature differ further in that, only cases with a diagnosis of pulmonary embolism were included to do indirect CTV. The present study did not calculate the radiation dose that the patients got. But according to a prior study in the literature, dosage values in a typical extremities CT examination, ranging from 7.25 to 8.26 millisieverts (mSv) were not excessive (13). No independent radiation dosage estimate was performed because these values were within permitted bounds.
Limitation(s)
Small sample size, patients with metallic implants, obesity, extreme leg oedema and patient compliance were the limiting factors in the present study.
The Multi-detector Computed Tomography-Pulmonary Angiography (MDCT-PA) is the first-line imaging study for patients with clinically suspected PE. Direct visualisation and quantification of thromboembolic material is the major advantage of this technique, combined CTPA-indirect CTV identify DVT at a moderate level of sensitivity and specificity. When early diagnosis is crucial to detect VTE, this method can be used as an alternative to CDUS. However, additional studies with larger sample sizes are needed to validate or confirm the findings of the present study.
DOI: 10.7860/JCDR/2023/61885.17627
Date of Submission: Nov 28, 2022
Date of Peer Review: Dec 15, 2022
Date of Acceptance: Feb 16, 2023
Date of Publishing: Mar 01, 2023
AUTHOR DECLARATION:
• Financial or Other Competing Interests: None
• Was Ethics Committee Approval obtained for this study? Yes
• Was informed consent obtained from the subjects involved in the study? Yes
• For any images presented appropriate consent has been obtained from the subjects. NA
PLAGIARISM CHECKING METHODS:
• Plagiarism X-checker: Nov 30, 2022
• Manual Googling: Jan 05, 2023
• iThenticate Software: Feb 14, 2023 (12%)
ETYMOLOGY: Author Origin
- Emerging Sources Citation Index (Web of Science, thomsonreuters)
- Index Copernicus ICV 2017: 134.54
- Academic Search Complete Database
- Directory of Open Access Journals (DOAJ)
- Embase
- EBSCOhost
- Google Scholar
- HINARI Access to Research in Health Programme
- Indian Science Abstracts (ISA)
- Journal seek Database
- Popline (reproductive health literature)
- www.omnimedicalsearch.com