| Popis: |
Venous and lymphatic valves have many common characteristics which can be studied with various direct and indirect methods. The indirect methods only recognize functional disorders provoked by valve damage. A disruption in the valve system produces venous or lymphatic stasis whose clinical manifestation depends on the localization and the extent of the valve damage. Blockade is another, generally less important mechanism leading to stasis. Valve insufficiency and blockade are often associated. The only point distinguishing between venous and lymphatic valve damage is the site. The peripheral, usually in the limbs, or terminal veins, for example in the heart, are usually involved while for the lymphatic vessels, the entire system may be involved including deep organs where visceral lymph stasis is observed. The general notions lead to indications for different imaging techniques. Functional explorations include ultrasound-Doppler, dynamic phlebography, isotopic lymphography and methylene blue test. Some clinical examples are presented describing the possibilities of these methods. The morphology of the valves is usually studied with phlebography and perhaps in the near future with magnetic resonance angiography. Endoscopy is the ideal method but is limited by the assessible venous territories. Search for the cause of blockade relies on computed tomography and magnetic resonance imaging which have progressively replaced lymphography and phlebography. In conclusion, the methods presented here, whether used in combination, are often in direct competition. They are all relatively aggressive examinations with a high cost. It is thus important to carefully choose the method according to the clinical indication and expected performance. |
