The Role of Venography in the Diagnosis of DVT in Trauma Patients

I.   Statement of the Problem

Venography is the diagnostic modality to which all other invasive or non-invasive diagnostic modalities for DVT are compared. It is often referred to as the "gold standard" for the diagnosis of DVT in trauma patients.

II.   Process

A Medline search from 1966 to present identified 3,520 articles related to venography in the diagnosis of DVT. Only eight articles were specifically related to the use of venography to diagnose DVT in the trauma patient. These articles, as well as some seminal review articles, were reviewed.

III.   Recommendations

A.   Level I

There are insufficient data to support a Level I recommendation on this topic.

B.   Level II

1.   Ascending venography should be used as a confirmatory study in those trauma patients who have an equivocal IPG or ultrasound for DVT.

2.   Ascending venography should not be used to screen asymptomatic trauma patients at high risk for DVT. There may be a role for ascending venography in research studies on the incidence of DVT in trauma patients.

IV.   Scientific Foundation

Ascending contrast venography as a diagnostic modality has been around since the 1920s but was considered to be unreliable or even dangerous until Rabinov and Paulin¹ standardized the technique in 1972. When this proper technique is utilized by a skilled radiologist, the entire lower extremity venous system should be visualized in a normal patient. Rabinov and Paulin¹ described the four cardinal signs of DVT: 1) constant filling defects 2) abrupt termination of the dye column 3) non-filling of the entire deep venous system or portions thereof, and 4) diversion of flow. Despite improvements in technique several logistical problems remain for venogram. A venogram requires transport of the patient to the radiology suite which is often difficult in critically ill trauma patients. Venography requires a cooperative patient who can be examined in a semi-erect position on a tilting fluoroscopy table. Venous access is not always possible especially in those with massive leg swelling. Usually 150-300cc of contrast material is required for adequate visualization of the deep venous system. With the use of nonionic contrast agents, the risk of allergic reactions and nephrotoxicity is very uncommon. Although the possibility of contrast-induced DVT exists,² the risks of this complication are unknown but likely to be low. Injection of the contrast media may result in local discomfort and, if significant extravasation of contrast occurs, skin necrosis may result. Despite its common label as "gold standard" in DVT diagnostic imaging, up to 30% of venograms will fail to visualize some segment of the venous system.³ Due to problems visualizing the entire venous system, a review of consecutive series of venograms by independent radiologists has resulted in only a 90% accuracy for venography.⁴ As a result, most radiologists now believe that accurate, noninvasive imaging procedures such as duplex ultrasound are the imaging procedure of choice for suspected DVT above the knee. However, the accuracy of venography in the calf appears to exceed noninvasive tests in most centers.⁵ Accordingly, it can be considered the "gold standard" for the diagnosis of calf DVT.

The most notable study in which venography was used as a screening technique in high risk trauma patients was that of Geerts et al.⁶ In this study, all patients admitted with

ISS>9 were assessed with contrast venography for evidence of DVT. No patient received any DVT prophylaxis. DVT was found in 201/349 patients (58%) and proximal DVT was found in 63(18%). Multivariate analysis identified five independent risk factors for DVT: increasing age, blood transfusion, surgery, fracture of the femur or tibia, and spinal cord injury. Most of these thrombi were asymptomatic. The authors did not articulate on the nature of the thrombi - how many were nonocclusive, or were small and confined to single venous segments below the knee. This has been a criticism of venography in that it may detect small isolated thrombi such as those on valve cusps that are clinically insignificant.³ It can be difficult to predict which ones will emerge as one of the 5-30%⁷ that go on to propagate an extensive, proximal (dangerous) thrombi. A decision to treat these patients is not insignificant as anticoagulant treatment can be associated with substantial morbidity in the trauma patient. Brathwaite et al.,⁸ in a cohort of 70 trauma patients treated with full anticoagulation, found a 36% complication rate requiring termination of anticoagulation. In a study of 39 immobilized patients, Kudsk et al.⁹ evaluated the lower extremities with venography between 7-12 days after injury. They found 63% of patients immobilized for 10 days or longer developed DVT, with thrombi extending above the knee in 50% of these patients. All but one of these DVTs were clinically silent. In 1967, Freeark et al.¹⁰ studied 124 trauma patients admitted for hospital stays of 3 weeks or longer. They found 44 (35%) had venographic signs of DVT. Less than one third of these patients had any clinical signs and symptoms related to a DVT. Although this study was performed prior to refinement in technique by Rabinov and Paulin it was one of the first to draw attention to the high rate of DVT in immobilized trauma patients. Likewise, serial lower limb venography was performed in 127 spinal cord injured patients by Yelnik et al.¹¹ They found a 33% incidence of DVT on first examination with another 13.8% developing DVT on subsequent exam.

V.   Summary

Although venography traditionally has been the diagnostic modality for DVT by which all other diagnostic modalities have been compared, logistical problems and complications associated with the procedure make it less appealing than other non-invasive diagnostic measures. Nevertheless, it still has a role in confirming DVT in trauma patients when diagnostic studies are equivocal, or possibly, as an outcome measure in clinical trials of thromboprophylaxis efficacy.

VI.   Future Investigation

A study comparing venography to other non-invasive imaging for DVT such as duplex ultrasound should be performed.

VI.   References

Reference Conclusions