Virchow's triad

Virchow's triad encompasses three broad categories of factors that are thought to contribute to venous thrombosis:

1. Alterations in normal blood flow (stasis)
2. Injuries to the vascular endothelium
3. Alterations in the constitution of blood (hypercoagulability)

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While the triad is now frequently applied to describe thrombosis arising within the arterial circulation, many continue to restrict it to that occurring within the venous vasculature.

The first category, alterations in normal blood flow, refers to several situations. These include turbulence, stasis, mitral stenosis, and varicose veins. The second category, injuries to endothelium includes damage to the veins arising from shear stress, hypertension. The last category, alterations in the constitution of blood, has numerous possible risk factors such as hyperviscosity, deficiency of antithrombin III, nephrotic syndrome, changes after severe trauma or burn, disseminated cancer, late pregnancy and delivery, race, age, whether the patient is a smoker, and obesity. All of these risk factors cause the situation called hypercoagulability.

History of the term

The origin of the term "Virchow's triad" is of historical interest. Rudolf Virchow elucidated the etiology of pulmonary thromboembolism, whereby thrombi occurring within the veins -- particularly those of the extremities -- become dislodged and migrate to the pulmonary vasculature. In detailing the pathophysiology surrounding pulmonary embolism, Virchow alluded to many of the factors known to contribute to venous thrombosis. While these factors had already been previously established in the medical literature by others, for unclear reasons they ultimately became known as Virchow's triad.

Thus, the elements comprising Virchow's triad were neither proposed by Virchow, nor did he ever suggest a triad to describe the pathogenesis of venous thrombosis. In fact, it was decades following Virchow's death before a consensus was reached proposing that thrombosis is the result of alterations in blood flow, vascular endothelial injury, or alterations in the constitution of the blood. Moreover, the eponym Virchow's triad did not emerge in the literature until almost 150 years after his original work.

Its nebulous origins notwithstanding, Virchow's triad remains a useful concept for clinicians and pathologists alike in understanding the contributors to venous, and perhaps arterial, thrombosis.

References

1. Dickson BC. Venous thrombosis: on the history of Virchow’s triad. UTMJ. 2004;81:166-171. [1]
2. Owen CA. A History of Blood Coagulation. Rochester, Mayo Foundation for Medical Education and Research. 2001:169-180.
3. Brotman DJ, Deitcher SR, Lip GY, Matzdorff AC. Virchow's triad revisited. South Med J. 2004;97:213-214.
4. Malone PC. Further reflections on Virchow's triad. South Med J. 2005;98:125.
5. Dickson BC. Virchow's triad? South Med J. 2004;97:915-6.
6. Virchow RLK. Gesammelte Abhandlungen zur Wissenschaftlichen Medicin. Frankfurt, Meidinger Sohn & Co., 1856. In, Virchow RLK. Thrombosis and Emboli (1846–1856). Matzdorff AC, Bell WR (transl). Canton, Science History Publications, 1998;5-11,110.