CT venography in suspected pulmonary thromboembolism
Section snippets
Rationale for CT pulmonary angiography
While much of the diagnosis and management of PE remains controversial, the tenet that 10% of acute PE are fatal before effective therapy can be initiated is widely accepted. In the 90% who survive the initial embolic event, detection and appropriate therapy can reduce mortality to 5% or less. For a generation, the standard diagnostic algorithm for suspected PE included three components: clinical suspicion/assessment, lung ventilation/perfusion (V/Q) scanning, and, when necessary, catheter
Rationale for combined CT pulmonary angiography and leg/abdominal/pelvic venography
PE and DVT are each part of the continuum of venous thromboembolic disease,22 and are each notoriously difficult to diagnose clinically. More than 90% of PE are thought to arise from deep venous thrombi in the legs and pelvis, and the primary prognostic factor for recurrent PE is probably residual DVT in the proximal legs.21, 22 Patients with DVT are asymptomatic up to 50% of the time8 and develop asymptomatic pulmonary emboli up to 50% of the time.22 Some authors have advocated sonography (US)
Experience of DVT imaging using CT prior to development of CTVPA
Venous thrombosis was first identified on CT relatively soon after its clinical introduction. Zerhouni et al31 described several cases of iliofemoral DVT as dilated veins containing low attenuation material and with higher attenuation, sharply defined walls, the latter attributed to the arterially supplied vasa vasorum. Years later, Baldt et al26 reported a technique which combined conventional venography and helical CT, where diluted contrast was injected concurrently into a dorsal vein in
Our experience with CTVPA
In 1998, we reported CTVPA for imaging patients with suspected venous thromboembolism.21 We acquired 10-mm axial images every 5 cm, from the diaphragm to the calves, starting 3 minutes after the beginning of the IV contrast injection for CTPA (Fig 1). Our criteria for DVT were an intraluminal filling defect or nonopacified vein, with wall enhancement or venous expansion as additional suggestive criteria. This preliminary report was followed by a series of 71 patients who also underwent US
Our current algorithm and CTV protocol
If a patient with suspected thromboembolism presents with signs and/or symptoms suggesting DVT, then lower extremity US is usually performed first, although this does not address the issue of whether PE is really present and if so to what extent. If CTPA is ordered, and there are no potential contraindications (e.g., pregnancy), then CTV is automatically included Fig 2, Fig 3 unless US has already been done. If there has been a recent US, CTV may be performed on a case-by-case basis (e.g.,
Experience of others
Our initial reports were followed closely by work from a group led by Cornell University Medical Center. Their retrospective review of routine pelvic CT and US performed within a week of each other showed 94% agreement for the presence or absence of DVT in the distal external iliac vein, the common femoral vein, and the proximal superficial femoral vein (52 patients).33 Cham et al34 then reported CTVPA in 541 patients, 116 with US correlation. These authors used contiguous 10-mm images from the
Limitations and pitfalls of CT venography
In all radiologic studies, there is a learning curve. The most common pitfall of CTV remains mixing artifacts, which occur in a minority of cases.27, 44, 45 These are usually ill-defined and at multiple levels. In these cases, or if the finding of a possible DVT is seen on only one image or venous level (in the absence of definite PE), some authors advocate corroborative sonography prior to the institution of therapy.44 Alternatively, rescanning the area(s) in question 1–2 minutes later may be
Continuing controversies
There are multiple technical issues involving CTV that have not been fully resolved. First, what parts of the body to routinely image? Some authors do not include the abdomen, pelvis, mid thighs, or calves. We believe that all of these areas should be scanned routinely. In the most recent series from Cham et al,35 23% of the 167 cases that were positive for DVT had isolated pelvic or superficial femoral venous (i.e., mid thigh) clot. Maki et al47 reviewed the results of 2704 US studies and
Summary
Combined CT venography and pulmonary angiography has become the standard CT imaging study for suspected venous thromboembolism at our institutions. While there are some continuing controversies regarding the most optimal and appropriate technique, the examination has been shown to be highly accurate in the evaluation of lower extremity DVT, compared with sonography. We believe the combination of CTPA and venous phase imaging allows the radiologist to perform a comprehensive evaluation of
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Cited by (10)
Prospective comparison of emergency physician-performed venous ultrasound and CT venography for deep venous thrombosis
2010, American Journal of Emergency MedicineCitation Excerpt :Historically, ventilation-perfusion (V/Q) scans and pulmonary angiography have been used. CT angiography (CTA) of the chest is now being used extensively, largely replacing V/Q scanning and conventional angiography [5]. Because DVT and PE represent different manifestations of the same disease process, there has been increasing interest in ruling out both processes simultaneously.
Suspected pulmonary embolism and deep venous thrombosis: A comprehensive MDCT diagnosis in the acute clinical setting
2008, European Journal of RadiologyCitation Excerpt :The relatively limited performance of the first spiral CTs prevented CTV in being effectively proposed as a follow-on adjunct to CTPA from the beginning, apart from few pioneers. As technical evolution progressed and comprehensive CT evaluation became feasible, after a few years, first convincing efforts were made to evaluate and propose the possible role of additional CTV as a valuable option to allow complete one-step evaluation of VTE, being the reported values of sensitivity and specificity and adopted gold-standards in first series quite non-homogeneous, as did proposed protocols [18]. The rationale for follow-on CTV after CTPA is threefold.
Prevention, Diagnosis and Treatment of Thromboembolic Complications in Traumatology and Orthopedics: Methodological Guidelines
2022, Travmatologiya i Ortopediya RossiiAcute lower extremity deep venous thrombosis
2015, Italian Journal of Vascular and Endovascular SurgeryContrast-enhanced sonographic diagnosis of unsuspected internal iliac vein thrombosis
2011, Journal of Clinical UltrasoundPulmonary embolism and deep venous thrombosis in trauma: Are they related?
2009, Archives of Surgery