Venous thromboembolism

Introduction

Venous thrombosis is the process of clot (thrombus) formation within veins. Although this can occur in any venous system, the predominant clinical events occur in the vessels of the leg, giving rise to deep vein thrombosis, or in the lungs, resulting in a pulmonary embolus. Collectively referred to as venous thromboembolism, these have a high prevalence both in the community and in hospitals, and bring a considerable burden of morbidity and possible mortality.

The causes of venous thromboembolism can be hereditary or acquired. A risk factor for thrombosis often can be identified in over 80% of patients, but usually more than one factor is at play in a patient.

Sources and selection criteria

Our information came from a personal collection of published work and searches of Medline using the key words “venous thromboembolism”, “deep vein thrombosis,” and “pulmonary embolus”. We also reviewed recent guidelines on management of venous thromboembolism and identified several relevant Cochrane reviews.

Deep vein thrombosis

A deep vein thrombosis commonly presents with pain, erythema, tenderness, and swelling of the affected limb. Findings on examination include a palpable cord (reflecting a thrombosed vein), warmth, ipsilateral oedema, or superficial venous dilation. Differential diagnoses include a ruptured Baker's cyst, muscle tears or pulls, and infective cellulitis. Objective diagnosis of deep vein thrombosis (as with pulmonary embolism) is important for optimal management, and although the clinical diagnosis is imprecise, models based on clinical features are fairly practical and reliable in predicting the likelihood of an event. Only a minority of patients (less than a third) with suspected deep vein thrombosis of a lower limb actually have the disease.

Compression ultrasonography remains the non-invasive tool of choice for the investigation and diagnosis of clinically suspected deep vein thrombosis. Although such imaging is highly sensitive for detecting proximal deep vein thrombosis, it is less accurate for isolated deep vein thrombosis …