What Is a Venous Venography?
Venous imaging–venography–is an imaging process for evaluating veins structurally and functionally. With suspected venous disease, ultrasound is the first step to explore whether further diagnostics are warranted. If so, venography via CT or MRI can be used to help design therapeutic or surgical strategies to treat the abnormality. Although oral contrast is sometimes used, venography usually requires the injection of contrast material which itself can cause deep vein thrombosis. This risk is small and is much less hazardous than allowing venous disease to remain undiagnosed.
Veins anywhere in the cardiovascular system can present with chronic venous disorders that interfere with functional return of deoxygenated blood to the heart and threaten the tissue affected by the compromise of venous drainage. When venous drainage is not optimal, the normal gaseous exchange between arterial and venous interaction at the tissues (oxygen and carbon dioxide) can fail, leading to injury of the tissues involved in this failure.
Age and immobility are two frequent causes of venous disorders. The valves within veins, which keep blood from backing up, can deteriorate with age in some people. They can also be destroyed by clots (thrombi), which leads to venous insufficiency and to increased pressure from the pooled blood, called venous hypertension. Immobility prevents the pumping action of the legs from contributing to the flow upwards toward the heart.
Chronic Venous Disorders Are Classified by a System Based On:
- Clinical signs
Chronic Venous Disease
Chronic venous disease refers to abnormalities in venous structure or function that present symptoms or signs requiring further investigation or treatment:
- Extremity tingling
- Pain, aching, or burning
- Skin irritation or changes
- Dilated veins (telangectasias, varicosities)
- Clinical edema
Chronic Venous Insufficiency
Chronic venous insufficiency refers to chronic venous disease with more serious clinical signs, such as significant edema and changes in the skin, including ulceration.
Diagnosis Using Venous Venography
Venous venography is used to identify and plan therapeutic protocols for venous insufficiency, venous hypertension, thrombosis, and varicose developments. Prior to that, the accuracy, affordability, and non-invasive nature of ultrasound is used as a both a screen and as a first step when signs and symptoms of a venous disorder present.
Duplex ultrasound is the combination of two ultrasonic technologies:
- B (brightness) mode: To reflect sound waves off of tissues of different densities to render an image of structure.
- Doppler flow ultrasonography: To evaluate motion of blood flow and to identify venous stasis and sluggishness or obstruction to this flow.
For patients who have venous insufficiency but uncertain ultrasound findings, a catheter can be used to enhance the imaging used in multidetector computed tomography (MDCT) or magnetic resonance (MR) venography. These techniques are used for confirming inconclusive venous disease, imaging difficult areas to visualize ultrasonographically, or for planning surgical interventions.
For suspicion of thrombosis in deep venous systems, such as the hepatic portal system or the intestinal mesenteric veins, CT (MDCT) and MR venography are needed to make a definitive diagnosis. These venous channels and their tributaries are simply too deep for ultrasound accuracy in conditions for which accuracy is crucial to prevent disastrous events such as bowel ischemia or liver complications (portal hypertension and other liver-related illness).
In some circumstances, arterial disease is either the precursor or the cause of venous disease, and persons with risk factors for peripheral arterial disease (smokers, diabetics, hypertensive, hyperlipidemia) should have arterial imaging included in the venous diagnostic approach.
When thrombosis within veins is diagnosed, blood tests for coagulation problems (hypercoagulability) are done which will both identify predisposing clotting disorders as well as serve to monitor the levels of anticoagulation medications used to dissolve the clot(s) or prevent their extension.
Medical Management and Treatment of Venous Disorders
The presence of venous insufficiency without thrombotic complications can initially be treated very conservatively:
- Leg elevation
- Compression stockings
- Scrupulous management of any ulcerations
Leg elevation prevents up to 40% of blood volume to pool in the leg’s veins. Compression stockings keep fragile veins at minimal diameter, reducing the amount of blood retained in them. Mobility helps re-establish the compression/decompression of leg muscles that act as a pump for upward propelling of blood back to the heart.
If there are ulcers, management and treatment involve cultures to identify or rule out infections that can be treated with antibiotics and debridement of any necrotic tissue that can jeopardize adjacent tissue and promote spread of the ulceration. Proper dressing is required to keep the ulcer bed moist for its best healing prospects.
Invasive Management and Treatment of Venous Insufficiency
When medical management fails, addressing the veins directly may be indicated by ablating (destroying) them chemically with sclerosing agents or surgically removing them. Vein destruction or removal reduces the amount of blood in the failing venous system, which helps prevent progression of varicosities and other chronic venous disease.
Management and Treatment of Thrombosis
Thrombosis (clot formation) is a much more serious development. It can cause venous disease or be a result of it. Regardless, thrombi represent imminent dangers:
- Obstruction to venous flow
- Risk of separation and migration to the lung circulation. Resulting in dyspnea or death from pulmonary emboli, or right ventricular disease (“cor pulmonale“) which is heart disease due to pathological lung conditions
Thrombosis requires anticoagulation, using anticoagulants such as warfarin or clopidogrel (Plavix); in thrombosis of crucial venous channels that risk organ damage, surgery or interventional catheterization techniques may be required in conjunction with reversing any therapeutic anticoagulation beforehand. If emboli are frequent and originating from deep vein thrombosis (DVT) in the legs, a filter can be placed in the vena cava as a weir to prevent life-threatening pulmonary emboli.
Prevention of Venous Disease
Prevention of venous disease for which venography may be necessary involves reducing the risks and number of predisposing factors. A genetic predisposition cannot be reduced, but factors that add to this risk can:
- Smoking cessation
- Change in lifestyle to incorporate physical exercise, minimize sedentary habits, and avoid high-risk behaviors that increase not only the risk of chronic venous disease but all health risks
- For women, awareness of the hypercoagulable states that the estrogen in oral contraceptives and menopausal hormone replacement can create. In pregnancy, applying medical safeguards (leg elevation, compression stocking, and mobility) throughout the second and third trimesters is prudent due to the increased coagulation inherent in this state. Any shortness of breath in women under any type of hormonal exposure should be reported immediately
- Weight management to decrease the impact of obesity on both tissue compromise and the risk of metabolic syndrome
- No engaging in illicit intravenous drug abuse
- Close surveillance of those undergoing chemotherapy or radiation
- Addressing any changes in bowel habits or stool abnormalities (bleeding, mucus, etc.) that may indicate thrombosis of the veins draining the intestinal tract
- In treatment of thrombosis with anticoagulants, it is critical to ensure the treatment is both sufficient (to dissolve the clot) but not excessive (to prevent bleeding or hemorrhage). Simple blood tests can be used serially to assess the amount of anticoagulation. In any planned invasive measures, anticoagulation must be allowed to reverse before proceeding, to prevent bleeding complications of the surgery or intravascular intervention itself
Prevention of Complications of Venography
Any allergies to contrast in the past or food allergies that implicate iodine (shell fish, etc.) should require venography in a setting appropriate to handle an immediate hypersensitivity reaction. Those with a history of hypersensitivity (flushing, itching, urticaria, bronchospasm/wheezing, laryngeal edema, or hypotension), should contrast be necessary, can be pre-medicated with corticosteroids (prednisone orally or IV methylprednisolone) and oral or IV diphenhydramine (Benadryl), followed by a small test dose and observation. This strategy is coupled with a change to a different type of contrast agent (non-iodated gadolinium-based agents).