WJG RSG Sandbox

# Overview
Deep vein thrombosis (DVT) is the formation of a blood clot ("thrombus") in a deep vein.

# Causes

## Life Threatening Causes
Deep venous thrombosis can be a life-threatening condition if thromboembolism and subsequent pulmonary embolism occur, and it must be treated as such irrespective of the underlying cause.

## Common Causes
- Blood clot

# FIRE: Focused Initial Rapid Evaluation
A Focused Initial Rapid Evaluation (FIRE) should be performed to identify patients in need of immediate intervention.

# Complete Diagnostic Approach for First Episode of DVT
Shown below are the different diagnostic approaches to the diagnosis of DVT depending on the pre-test probability of the disease.

## Low Pretest Probability

## Moderate Pretest Probability

## High Pretest Probability

# Complete Diagnostic Approach for Recurrent DVT
Shown below is the diagnostic approach to suspected recurrent DVT.  The recommended initial test is either proximal ultrasound (US) or highly sensitive D-dimer tetsing rather than venography, CT venography or MR imagining.  Initial D-dimer testing is recommended over proximal US in case there is no prior ultrasound for comparison.  Note the following definitions:
- Negative US:
Normal US, or
Increase in residual diameter of less than 2 mman, or
Area of prior noncompressibility with a decreased or stable residual diameter
- Normal US, or
- Increase in residual diameter of less than 2 mman, or
- Area of prior noncompressibility with a decreased or stable residual diameter
- Nondiagnostic US:
Ultrasound that is technically limited, or
Area of prior noncompressibility with an increment in residual venous diameter of < 4 mm yet  2 mm, or
Area of prior noncompressibility in the absence of a previous  measurement of the residual diameter
- Ultrasound that is technically limited, or
- Area of prior noncompressibility with an increment in residual venous diameter of < 4 mm yet  2 mm, or
- Area of prior noncompressibility in the absence of a previous  measurement of the residual diameter
- Positive US:
New noncompressible segment, or
Area of prior noncompressibility with an increment in residual venous diameter of  4 mm
- New noncompressible segment, or
- Area of prior noncompressibility with an increment in residual venous diameter of  4 mm

## Diagnostic Approach for Non Diagnostic Ultrasound

## Diagnostic Approach for Venography

# Long Term Treatment
Shown below is the long term treatment for DVT.  Note that not all patients with isolated distal DVT are started on anticoagulation, only those who are started require long term therapy with anticoagulation.  Patients who are planned to receive long term therapy with anticoagulation should be assessed regularly for the risks vs benefits of anticoagulation therapy.

## Assessment of Risk of Bleeding
The risk factors of bleeding with anticoagulation therapy are:
- Age > 75 years
- Alcohol abuse
- Anemia
- Antiplatelet therapy
- Cancer
- Comorbidity and reduced functional capacity
- Diabetes
- Frequent falls
- Liver failure
- Metastatic cancer
- Poor anticoagulant control
- Previous bleeding
- Prior stroke
- Recent surgery
- Renal failure
- Thrombocytopenia
Shown below is a table summarizing the risk of bleed based on the number of risk factors. Note that, although the presence of one risk factor signify moderate risk of bleeding, if the single risk factor is severe (such as severe thrombocytopenia or recent major surgery) then the patient is at high risk of bleeding despite the presence of a single risk factor.

# Do's
- Among patients with low pretest probability of DVT, the preferred initial test is D-dimer.  However, among those patients who have comorbidities known to increase D-dimer concentration in the absence of a venous thromboembolism, ultrasound is preferred as an initial test.
- Patients with low pretest probability of DVT among whom an ultrasound can not be practically performed, for example due to the presence of a leg cast, or those who have non-diagnostic ultrasound results, CT scan venography, magnetic resonance venography, or magnetic resonance direct thrombus imaging can be considered instead of venography.
- Among patients with moderate pretest probability of DVT, whole leg US might be preferred over proximal US in case there is severe symptoms consistent with calf pain or in case the patients have difficulty returning for the serial US tests.  Patients among whom an ultrasound can not be practically performed, for example due to the presence of a leg cast, or those who have non-diagnostic ultrasound results, CT scan venography, magnetic resonance venography, or magnetic resonance direct thrombus imaging can be considered instead of venography.
- Among patients who underwent whole leg ultrasound that revealed isolated distal DVT, consider serial US testing over trearment to check for extension of the thrombus.  However, if the pretest probability is high or there is elevated risk of extension or severe symptoms, consider treatment over serial US testing.

# Don'ts