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Venography 1 Investigating disorders of veins In recent years improved CT techniques, and without radiation exposure by ultrasound and MRA made Contrast phlebography by direct venous injection is nevertheless still widely used. The types of contrast phlebography used in clinical practice include: Direct contrast phlebography: I. Phlebography of the lower Iimb. 2. Pelvic phlebography and inferior vena cavography. 3. Hepatic, renal and gonadal vein phlebography. 4. Phlebography of the upper limb and superior vena cava. 5. Portal phlebography. Indirect phlebography: can he achieved by serial filming following arteriography. The latter method is the one routinely used for the demonstration of the cerebral veins following cerebral angiography and commonly for the demonstration of the renal veins following selective renal arteriography. It is also used for portal phlebography following selective celiac arteriography. The lower limb phlebography It should be stated at the outset that lower limb venography, particularly for suspected thrombosis, is being rapidly supplanted by ultrasound techniques and in many centers the venographic technique is virtually obsolete. Phlebography of the lower limb is practiced at most medical Centers for the following purposes: I. To demonstrate deep venous thrombosis (DVT) in the calf, thigh, pelvis or inferior vena cava. Dr. ABEER EL SOBKY Venography 2 2. To investigate secondary or recurrent varicose veins thought to be associated with an abnormality of the deep-venous System. 3. To investigate swollen legs where the differential diagnosis between lymph edema, cellulitis and venous incompetence (or obstruction) is not clear. 4. To outline venous malformations. 5. In some cases, however, for example in patients with repeated pulmonary emboli but no obvious source, the investigation may be undertaken to exclude the lower limb as a source of emboli. Normal anatomy The venous drainage of the lower limb can be divided into two separate systems, the deep veins and the superficial veins. These are connected by the communicating veins. The deep veins in the calf follow the same distribution as the main arteries but are usually double, forming the anterior tibial, posterior tibial and peroneal veins. The communicating veins are usually small and paired and connect the superficial and deep veins. Normally they are extremely narrow, but they can become quite large when hypertrophied. They are valved so that blood only flows from the superficial to the deep veins. Under pathological conditions they can become incompetent, permitting reverse flow from the deep to the superficial veins. The popliteal vein is a smooth large vessel lying behind the knee and passing up into the femoral vein, which follows the course of the femoral artery. The superficial leg veins drain into the saphenous veins. The short saphenous vein passes up the lateral side of the leg to the knee, where it passes deeply to join the popliteal vein. Dr. ABEER EL SOBKY Venography 3 The long saphenous vein passes up the medial side of the calf and thigh and then joins the femoral vein below the groin. The venous system can be regarded as a blood reservoir, and normally contains some two-thirds of the body's blood, largely in the lower limbs. Flow to the heart depends on the pressure gradient between the veins and right atrium, and is assisted by the muscle contractions, particularly in the calf, acting as a pump. The veins themselves can also actively contract and help onward flow of blood. In addition, the valves are of great importance in preventing retrograde flow, and their destruction or damage by thrombosis has serious hemodynamic consequences leading to venous incompetence. Technique Ascending phlebography A large number of different techniques have been described in the literature. No standard technique has been generally accepted. The technique has been modified over the years, and is as follows: 1. A small needle is inserted percutaneously into a vein on the dorsum of the foot. Occasionally this may prove impossible, and the needle may have to be inserted by cut-down. If the foot is swollen or edematous, prior bed rest with the foot elevated is desirable to reduce the swelling. 2. Once the needle is in position, compression is applied just above the ankle and also just above the knee by tourniquets or by inflatable cuffs. The pressure used is just sufficient to occlude the superficial veins completely without affecting the patency of the deep veins. Dr. ABEER EL SOBKY Venography 4 3. Contrast medium (40-50 ml) is then injected by hand pressure (in 20-30 s). In some cases more may be required to obtain adequate filling of the femoral and iliac veins, but it should rarely be necessary to use more than 80-100 ml. Flow is monitored by observation with an image intensifier, and films obtained at appropriate moments as the veins are sequentially filled. 4. While some workers conduct the examination with the patient supine, others insist that the patient should be tilted on the table into a 30-60° feet-down position. This is mainly to prevent layering of contrast medium posteriorly, which gives rise to artefactual filling defects, and to ensure mixing of blood and contrast medium. 5. The foot and leg should be medially rotated to separate the tibia and fibula and the deep veins of the calf. 6. The weight should not be borne by the foot being injected, so that the calf muscles remain relaxed and their veins can be filled with contrast. Descending phlebography This is less frequently practiced but is occasionally used, with the patient supine on a tilting table and the feet against the footrest. The femoral vein is punctured at the groin. The catheter tip is advanced 5 cm into the artery and the catheter strapped down to the skin. The patient is then tilted to the erect or near-erect position, and contrast medium injected. If the patient performs the Valsalva maneuver, contrast medium will reflux down an incompetent femoral vein into the popliteal vein. It has been claimed, however, that contrast will sometimes flow past competent valves, though it is usually Dr. ABEER EL SOBKY Venography 5 possible to assess the degree of true incompetence and show the valves clearly, particularly when they are competent. Complications With the older contrast media, a few patients tolerated the procedure badly and complained of pain and discomfort in the calf with ascending phlebography. Nausea, vomiting and minor allergic reactions were also occasionally seen, as with all contrast media. The new low-osmolality contrast media should be better tolerated and give rise to little discomfort. Care should be taken to ensure there is no contrast medium extravasation at the site of puncture, as this can be quite painful, and with a large volume of extravasation, an ischemic or edematous foot, can be serious. Skin necrosis has been recorded to result from this accident. Phlebitis and postphlebography venous thrombosis can occur where large volumes of high-concentration contrast are used. This should be guarded against by flushing out residual contrast agent with saline at the end of the procedure, and by using the new low osmolality contrast media. Radiological findings In the normal patient the deep veins of the calf are outlined by contrast at ascending phlebography with cuffs inflated; three paired veins accompanying the peroneal, posterior and anterior tibial arteries can be recognized, the last being smaller than the others. There is no filling of the superficial or communicating veins. The popliteal vein is single and commences near the knee joint, passing upwards to become the femoral vein. Views of the calf are usually obtained in both anteroposterior and lateral projections. Dr. ABEER EL SOBKY Venography 6 Valves are usually obvious in the distended veins but can be accentuated by the patient performing the Valsalva maneuver. A good-quality ascending phlebogram will also demonstrate the iliac veins and inferior vena cava. If the suspected lesion affects only the pelvic veins or inferior vena cava, direct pelvic phlebography is to be preferred (see below). Deep venous thrombosis Venous thrombosis appears to be multifactorial in origin, and is associated with slowing of the blood flow and an increased liability to blood coagulation. Conditions known to predispose include malignant disease, age, obesity, trauma and surgery, as well as prolonged immobilization, myocardial infarction and congestive heart failure. Clinically, symptoms are present only if there is significant obstruction or inflammation produced by the thrombosis, and it is claimed that 50% or more of cases are silent and symptomless. Varicose veins Varicose veins occur in 4% of the adult population and can give rise to significant morbidity owing to ulceration, hemorrhage, thrombosis and eczema. Varicose veins are described as being either primary or secondary in nature. Primary varicose veins are always the long and short saphenous veins and are frequently associated with incompetent perforating veins; the deep venous system is, however, normal. Secondary varicose veins, on the other hand, occur as a result of previous DVT. Dr. ABEER EL SOBKY Venography 7 Varicography may be employed; this involves the direct puncture of a varix with a 21 G or 23 G needle so that the perforator responsible can be identified and dealt with. UPPER LIMB VENOGRAPHY Anatomy As in the lower limb, there is a superficial and deep system of veins, both of which drain into the axillary vein, although in the arm it is the superficial system that drains most of the blood. Paired deep veins accompany the ulnar, radial and brachial arteries. Two major superficial veins, the basilic vein and the cephalic vein, communicate at the antecubital fossa via the median cubital vein. The cephalic vein ascends on the lateral aspect of the arm to drain into the axillary vein. The basilic vein ascends medially to join the deep brachial veins to become the axillary vein. The axillary vein continues as the subclavian vein. This vessel in turn is joined by the internal jugular vein to form the brachiocephalic or innominate vein. The right and left brachiocephalic veins unite to form the superior vena cava. Technique The most common indications for upper limb venography are: Assessment of the central veins when there are symptoms or signs of venous occlusion (e.g. superior vena caval obstruction). Dialysis shunts and fistulas: The visualization of arm and central veins before the fashioning of an arteriovenous fistula for dialysis and the assessment of poorly functioning dialysis shunts and fistulas. When studying the central veins, DSA greatly facilitates the examination; bilateral antecubital fossa veins should be cannulated and simultaneous injections of approximately 30 ml of contrast medium are made during image acquisition at two frames per second. Dr. ABEER EL SOBKY Venography 8 PELVIC VENOGRAPHY Techniques The external and common iliac veins and inferior vena cava can be demonstrated by means of ascending phlebography from a pedal injection or by direct puncture at the groin. They can also be catheterized retrogradely using a catheter inserted from the contralateral groin, jugular vein or arm. The internal iliac veins and their tributaries can also be selectively, retrogradely cannulated and opacified. Dr. ABEER EL SOBKY