Investigation of venous disease
A full history should always be taken, enquiring about any injury to the leg or swelling which may suggest a previous episode of deep vein thrombosis. Patients report a wide range of symptoms associated with venous disease. These include tiredness, aching, tingling and ankle swelling which get progressively worse towards the end of the day and are relieved by elevating the leg. Sometimes patients report cramps in the legs, which are usually worse at night. Patients with more severe venous disease may notice the skin changes that occur. Pain in the calf on walking is usually attributable to lower limb arterial disease, referred to as intermittent claudication. Patients with severe deep vein obstruction may also develop bursting pain in the calf on walking, due to the very high venous pressures that may occur under these conditions.
A clinical examination carried out with the patient standing will reveal the extent of any varicose veins and whether they are associated with the long or short saphenous systems. Further information may be gained by using a tourniquet test (Brodie, 1846; Trendelenburg, 1890) to determine the source of varices. The tourniquet is often replaced by the hand of the examiner used to compress the long or short saphenous vein. The patient lies and the leg is elevated to empty the veins. The tourniquet is applied high on the thigh and the patient stands again. The speed at which the varices fill is observed. In the case of varices from the long saphenous vein these fill within a few seconds without a tourniquet, but with the trunk of the long saphenous vein compressed in the thigh much slower filling takes place over 15 or 20 seconds. If filling is not controlled by an above-knee tourniquet, then a tourniquet is applied to compress the short saphenous vein, just below the knee. If the varices now fill slowly then the source of venous reflux is from the SPJ. If the varices continue to fill rapidly some further source must be the cause. The patient may have incompetent deep veins or a calf perforating vein. The success of tourniquet tests lies in the ability of the examiner to assess the varices and their rate of filling. This may be easy in the case of large varices, but can be vary difficult with smaller varices. Considerable practice is required for successful application of these tests.
The clinical examination should continue by noting the presence and extent of any skin changes or ulceration at the ankle. An examination of the peripheral pulses should be carried out. Venous and arterial disease of the lower limb often coexist, especially in more elderly patients. An abdominal examination completes the clinical examination in patients presenting with lower limb varices, as these may occasionally be the result of an abdominal neoplasm causing venous obstruction.
More detailed information than can be obtained from clinical examination is useful in the management of patients with primary varicose veins and essential in the management of patients with recurrent varices, a history of lower limb venous thrombosis or venous leg ulcers.
A Doppler assessment is now the minimum level of investigation required before treating somebody with venous disease. A Doppler flow probe can be used to exclude arterial disease and to determine the patency of a vein, and a bidirectional flow probe used to detect venous reflux. This investigation is carried out with the patient standing. The Doppler probe is first placed over the SPJ and the blood flow assessed to locate the venous flow in the common femoral vein. With one hand the examiner gently squeezes the calf to produce an acceleration of blood flow in the veins. This is heard as a ‘whoosh’ from the loudspeaker of the Doppler machine. The calf compression is released and any reverse flow in the veins sought. With practice it is possible reliably to identify venous reflux in the SFJ. The examination may be repeated with the probe held over the long saphenous vein in the mid-thigh region, to confirm that the venous reflux lies in the superficial vessels. Some surgeons use a tourniquet to occlude the superficial veins, in the same way as when performing a Trendelenburg test. The probe may also be held over the SPJ while the calf is compressed and released to test the competence of veins in this region. In the popliteal fossa it is more difficult to distinguish between deep and superficial venous incompetence.
This method is very useful when examining patients with primary varicose veins, especially those which are thought to result from SFJ incompetence. The popliteal fossa contains many veins and if venous reflux is heard it is difficult to be certain from which veins it arises. However, in patients with primary varices saphenopopliteal incompetence is usually readily identified. All surgeons who regularly treat patients with varicose veins should be competent at this type of investigation. Where the source of recurrent varices or a leg ulcer is sought, duplex ultrasonography is usually more reliable.
Photoplethysmography and other plethysmographic techniques
In this investigation a probe is attached to the skin to assess venous filling of the surface venules by measuring light transmission of the skin. The filling of these vessels reflects the pressure in the superficial veins of the leg. The patient sits quietly until the trace stabilises. Then he or she performs a series of 10 dorsiflexions at the ankle. The venous pressure falls in the superficial veins of the leg and the skin venules empty, so the photoplethysmography (PPG) trace falls. The patient then sits and the veins refill. Under normal conditions venous refilling occurs through arterial inflow alone, a slow process taking 20 or 30 seconds when the limb is at rest. In patients with venous incompetence the veins also fill via venous reflux, which speeds the refilling process. Fast refilling times mean that one or more veins in the leg are incompetent. The test can be repeated after the application of a tourniquet above the knee to occlude the long saphenous vein, and then below the knee to occlude both the long and short saphenous veins. This helps to establish which set of superficial veins is incompetent.
A number of other plethysmographic tests is used t evaluate the venous system physiology including the ai plethysmograph, light reflex rheography and strain gaug plethysmograph. These are usually used by vascular surgeon in vascular laboratories or by specialists in venous diseases All are used to quantify the impairment of venous function caused by obstructed or incompetent venous valves.
Duplex ultrasound imaging
This technique involves the use of high-resolution B-mode ultrasound imaging and Doppler ultrasound to obtain images of veins and simultaneously measure flow in these vessels. It allows direct visualisation of the veins and provides functional, as well as anatomical, information. Modern duplex ultrasound machines represent blood flow as a colour map which is superimposed on the greyscale image of the vessel. This technique is highly reliable in the investigation of arteries and veins, and is the most appropriate investigation to use when detailed analysis of the anatomy and physiology of the venous system is required.
The examination is performed with the patient standing. In this position the veins are filled and easily seen on the ultrasound image. The flow in the veins is assessed in exactly the same way as when using a hand-held Doppler probe. The examiner images the vein that he or she wishes to study and compresses the calf with his/her hand to produce forward flow. This results in upward flow towards the heart in a normal vein, and is shown as blue in the colour flow map. The calf is then released to test the competence of the valves. Competent veins show no flow, but incompetent veins allow reverse flow which is represented as red in the colour flow map. All lower limb veins may he imaged with ease using modern ultrasound machines, and therefore the patency and competence of all lower limb veins may be tested. The examiner steadily works his/her way from the groin to the ankle testing each major deep and superficial vein along the limb. This allows a comprehensive map of the veins to the leg to be constructed. Blocked or incompetent veins can be readily identified by a skilled vascular technologist. The origin of varicose veins and venous ulceration can be identified, and in patients with suspected deep vein thrombosis the presence of thrombus can be seen.
This investigation is the X-ray equivalent of duplex ultrasonography. Historically it preceded ultrasonography and has been widely used in the past for the assessment of patients with vein problems. An ascending venogram is performed by canulating a vein in the foot in order to inject X-ray contrast medium. A narrow tourniquet is applied just above the malleoli to direct blood flow into the deep veins and an injection of nonionic contrast material given to outline the veins. The technique provides excellent anatomical information but gives much less information about the veins where the valves have failed. It is a useful examination for suspected deep vein thrombosis where ultrasonography is not available.
Incompetent veins can be shown by descending venography. Here a cannula is inserted in the femoral vein and contrast material injected with the patient standing. The contrast material is heavier than blood and flows down the limb though incompetent valves. Both ascending and descending phlebography is required to establish as much information as is provided by duplex ultrasonography.
The source of recurrent varicose veins may be identified by a varicogram. Contrast material is injected into one of the varicosities and followed to identify its source. Again, duplex ultrasonography has largely replaced this investigation.
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