Venography

Venography (phlebography) is a radiographic or fluoroscopic study of veins after injection of water soluble iodinated contrast. The agent is a non-ionic low osmolar contrast, 150 to 300 mg of iodine in each mL, in volumes of 50 to 150 mL for the leg, depending on the technique.

Ascending venography of the leg uses a cannula in a vein on the dorsum of the foot and a tourniquet at the ankle to direct contrast into the deep veins. Sequential images are taken as contrast rises from the calf to the iliac veins and inferior vena cava, with the patient tilted head up at about 40 degrees.

Descending venography (contrast injected into the common femoral vein with the patient on a tilting table, with a Valsalva manoeuvre) shows valvular reflux. Upper limb venography, central venography (of the subclavian veins, brachiocephalic veins and superior vena cava), renal, adrenal, gonadal and hepatic venography, and cavography are done through a catheter.

The effective dose is about 1 to 5 mSv, depending on the region and number of images.

Venous thromboembolism affects about 1 to 2 in 1000 people each year, and clinical diagnosis is unreliable (only about a quarter of patients with suspected deep vein thrombosis have it).

Ultrasound with compression has replaced venography as the first test for deep vein thrombosis, with a sensitivity over 95% for proximal thrombus, and CT or MR venography are used for the pelvic veins, vena cava and central veins.

Contrast venography remains the reference test when ultrasound is non-diagnostic, in some centres for isolated calf vein thrombosis and, with intervention, for stenting of venous obstruction, thrombolysis, filter placement, varicose vein and venous malformation work, and for mapping before surgery.

Indications. Suspected deep vein thrombosis when ultrasound is inconclusive or not available (in the calf, the iliac veins or the vena cava). Suspected pelvic vein, inferior vena cava or iliac vein thrombosis or compression (May-Thurner syndrome). Upper limb or central vein thrombosis or stenosis (catheter related thrombosis, effort thrombosis, superior vena cava obstruction).

Planning and follow up of venous intervention: thrombolysis, thrombectomy, stenting, inferior vena cava filter placement and removal. Chronic venous insufficiency and recurrent varicose veins (mapping, incompetent perforators, pelvic reflux). Venous malformation. Pelvic congestion syndrome (ovarian and internal iliac venography with embolisation).

Varicocele (testicular vein venography and embolisation). Venous sampling (adrenal, renal, parathyroid and pituitary petrosal sinus sampling for hormone sources). Assessment of dialysis access veins. Not as a screening test, and not when ultrasound answers the question.

Contraindications and precautions. Allergy to iodinated contrast (premedication or alternative imaging such as MR venography or carbon dioxide venography). Renal impairment (eGFR under 30 mL each minute for 1.73 m2): the risk of contrast nephropathy is increased, and ultrasound or non-contrast MR is chosen. Pregnancy: avoid unless essential.

Active infection or cellulitis at the cannulation site. Severe heart failure (volume load of contrast) and pulmonary hypertension (risk with large volumes). Metformin: handled as the local rule requires. Contrast extravasation can cause tissue injury and pain, and a phlebitis occurs in a minority of patients after peripheral injection. Severe leg ischaemia or oedema may make cannulation difficult.

Patients with a patent foramen ovale should not have air in the lines. Thrombolysis or intervention requires coagulation and platelet checks.

Preparation and technique. The patient is hydrated, a large bore cannula (18 to 20 gauge) is placed in a vein on the dorsum of the foot, and the leg is positioned.

For ascending venography:

• Tourniquets at the ankle (and sometimes the knee) direct contrast into the deep veins.
• 50 to 100 mL of contrast are infused over about 1 to 2 minutes.
• Films are taken of the calf, knee, thigh and pelvis in at least two projections with the leg internally rotated.
• The leg is elevated and flushed with saline or heparinised saline afterwards to avoid post-venographic phlebitis.

In catheter venography, the vein is punctured under ultrasound control (femoral, jugular, brachial or antecubital), a catheter is placed, and contrast is injected by hand or pump with digital subtraction images. A Valsalva manoeuvre and a tilting table help show reflux.

Normal appearances. Deep veins fill with contrast in a smooth, continuous column, all with regular margins and without filling defects. They are:

• Paired calf veins (anterior tibial, posterior tibial and peroneal).
• The popliteal vein.
• The superficial femoral vein (a deep vein despite its name).
• The common femoral vein.
• The external and common iliac veins.
• The inferior vena cava.

Valve cusps are seen as thin lucent lines at bifurcations, and the sinuses behind the valves look like small bulges ("bamboo" pattern). Muscle veins in the calf fill in a soleal pattern. Superficial veins (great and small saphenous) fill when the tourniquet is released or in the superficial system, and perforating veins connect them through the fascia.

Contrast flows upward steadily and clears in a few minutes, and the iliac veins and the inferior vena cava fill with the contrast mixed with unopacified blood from the opposite side ("streaming").

Interpretation.

• Acute deep vein thrombosis: a constant filling defect seen on at least two projections (an intraluminal lucency outlined by contrast, a "railway track" sign when contrast flows around the thrombus).
• Other signs of acute thrombosis: an abrupt cutoff of a vein with non-filling of the veins proximal to it, absent opacification of a segment, and collaterals.
• A free floating thrombus has a contrast halo around it and carries a high embolic risk.
• Chronic thrombosis and post-thrombotic syndrome: narrowed, irregular veins, partial recanalisation with webs and bands, thickened walls, loss of valves, and numerous collaterals; venography is not specific, and it is difficult to date a thrombus.
• Iliac vein compression (May-Thurner): a narrowed left common iliac vein where it is crossed by the right common iliac artery, with pelvic and cross-pelvic collaterals and filling defects representing venous spurs.
• Inferior vena cava thrombosis and anomalies: an occluded or narrowed cava, duplication or left sided cava, azygos continuation, and retroaortic left renal vein.
• Upper limb and central vein disease: thrombosis of the axillary, subclavian and brachiocephalic veins, stenosis from a catheter, and tumour invasion.
• Effort related thrombosis: compression at the costoclavicular space seen only with the arm abducted.
• Superior vena cava obstruction with large collaterals (azygos, internal mammary, lateral thoracic).
• Venous insufficiency: reflux of contrast down the femoral vein with Valsalva (grades 0 to 4 by how far down the leg contrast flows), incompetent perforators, incompetent saphenous veins, and varicose veins.
• Venous malformation and angiodysplasia: dilated, irregular venous channels and lakes, with slow flow, phleboliths and abnormal drainage; low flow lesions are treated by sclerotherapy.
• Pelvic congestion syndrome and varicocele: dilated, tortuous ovarian or testicular veins with reflux of contrast.
• Venous stenosis and occlusion of dialysis access: a narrowed outflow vein, a central vein stenosis, and thrombosis.
• Tumour invasion of veins: a filling defect that continues into a mass (renal cell carcinoma extending into the renal vein and cava, hepatocellular carcinoma into the hepatic and portal veins), with enlarged collaterals.
• Catheter and device complications: a fibrin sleeve around a central line, a mispositioned catheter, and a filter in place (tilted, fractured, thrombosed or penetrating).
• Venous sampling: hormone gradients between sides (adrenal vein sampling for aldosterone and cortisol, parathyroid venous sampling, petrosal sinus sampling for ACTH) are measured in the laboratory.

Critical values and findings needing immediate action.

• Proximal deep vein thrombosis (popliteal vein or higher) or free floating thrombus: anticoagulation at once (unless contraindicated), with consideration of a vena cava filter when anticoagulation is contraindicated or has failed.
• Phlegmasia cerulea dolens (severe swelling, cyanosis, venous gangrene): urgent catheter directed thrombolysis or thrombectomy and vascular review.
• Inferior vena cava or iliac vein thrombosis extending into the renal or hepatic veins: anticoagulation and specialist review.
• Pulmonary embolism symptoms during or after the study (dyspnoea, chest pain, hypoxia): oxygen, anticoagulation and CT pulmonary angiography.
• Superior vena cava obstruction with stridor, facial swelling and raised intracranial pressure: urgent stenting or treatment of the cause (oncology).
• Anaphylaxis to contrast: stop the injection, adrenaline, oxygen and fluids.
• Contrast extravasation with compartment syndrome: stop injection, elevate the limb, and arrange surgical review for fasciotomy.

Limitations and artefacts.

• Technical failure rates are 5 to 10% (inadequate filling of the deep system, especially in the iliac veins or in a swollen leg), and unfilled veins do not prove thrombosis.
• A filling defect must be present on at least two views; a lucent area that appears on only one view, or is due to unopacified blood, contrast mixing, or a tourniquet effect, mimics thrombus (streaming artefact).
• Contrast inflow from a superficial vein or the muscle vein fills instead of the deep vein if the tourniquet is too loose, and the study is non-diagnostic.
• Venography is painful in about a fifth of patients, and causes post-venographic phlebitis (2 to 5%, reduced with saline flush), extravasation, hypersensitivity (1 to 3% mild, rare severe), contrast nephropathy, and thrombosis from the procedure (rare).
• It cannot date a thrombus reliably, and chronic changes mimic acute thrombus.
• Ultrasound has replaced it for most cases because it is non-invasive, portable, repeatable and does not need contrast or radiation.
• The calf veins and the iliac veins are the weak points of ultrasound (iliac veins are better shown by CT or MR venography, which show the vein wall and surrounding structures).
• Radiation dose is moderate and an ionising radiation study in young women or during follow up should be limited.
• Wrongly positioned catheters, rapid injection, and patient movement degrade the images.
• Carbon dioxide venography avoids iodinated contrast in renal impairment but gives lower image quality.

Special groups.

• Pregnant women: ultrasound first, and MR venography without contrast for pelvic veins; venography only if essential, with abdominal shielding.
• Patients with renal impairment: carbon dioxide venography, ultrasound or non-contrast MR venography.
• Cancer patients: high risk of thrombosis, central venous catheter thrombosis and vena cava invasion.
• Patients with obesity or severe oedema: ultrasound is difficult and venography may be the alternative.
• Patients with suspected thrombosis in unusual sites (upper limb, cerebral venous sinus, portal, mesenteric): CT or MR venography are preferred.
• Children: rare, with ultrasound and MR first.
• Regions: deep vein thrombosis after surgery, trauma, immobility, long travel, pregnancy and puerperium, and cancer; filarial lymphoedema and varicose disease are common; venography is used for venous workup when ultrasound expertise is limited.

Follow up tests.

• Duplex ultrasound of the leg veins (repeat after 5 to 7 days when initial ultrasound is negative and suspicion is high).
• D-dimer (to exclude thrombosis in low risk patients).
• CT or MR venography.
• CT pulmonary angiography for suspected pulmonary embolism.
• Echocardiography.
• Full blood count, coagulation tests, antithrombin, protein C and S, factor V Leiden.
• Antiphospholipid antibodies (selected cases).
• Renal function and liver function.
• Tumour screening when thrombosis is unprovoked.
• Referral to vascular surgery, haematology or interventional radiology.