Complications of Venous Thrombosis

Mechanisms of formation and threats

The nature of venous thrombosis complications depends on the type of pathological process: whether it occurs with inflammation of the vascular wall (thrombophlebitis) or primarily without it (phlebothrombosis). The development of phlebothrombosis is based on pronounced venous stasis (characteristic of cardiac decompensation and prolonged bed rest), hypercoagulation (against the background of oncological processes, atherosclerosis), and local hemodynamic disorders, for example, in varicose veins.

The localization of the primary focus largely determines the scenario for the development of complications. The vast majority of thrombi (up to 90%) form in the deep veins of the lower legs and the iliofemoral segment. The lack of pathogenetic therapy leads to the migration of thrombotic masses to other vascular beds or to persistent disruption of local tissue trophism.

Pulmonary embolism (PE)

PE is the most fatal complication of deep vein thrombosis of the pelvis and lower extremities. Much less frequently, the source of emboli is mural thrombi of the right heart chambers, the inferior vena cava, or the hepatic veins.

A key role in the pathogenesis of sudden embolism is played by floating thrombi. Unlike occluding clots, which are completely fixed to the endothelium along their entire length, a floating thrombus is attached to the vein wall by only one base. Its free end oscillates in the blood flow, creating ideal biomechanical conditions for detachment.

The catastrophe often occurs at the moment of a sharp change in intra-abdominal pressure and hemodynamics. The classic clinical scenario: a patient with congestive heart failure after prolonged bed rest suddenly stands up. At this moment, the muscle-venous pump of the lower legs is activated, which sharply increases venous return. A powerful stream of blood detaches the floating thrombus, which rapidly migrates through the inferior vena cava to the right heart chambers and further into the pulmonary trunk. Clinically, the process manifests with acute cyanosis of the upper half of the body, dyspnea, and often ends in a lethal outcome.

Generalization of infection and septic emboli

If thrombosis complicates the course of bacterial phlebitis, blood clots become a reservoir for microorganisms. Fragmentation of such an inflamed thrombus leads to the spread of septic emboli through the systemic circulation with the formation of secondary purulent foci (abscesses) in internal organs.

• Cranial veins and venous sinuses: Thrombophlebitis of this localization develops as a severe complication of purulent infections (otitis media, mastoiditis, sinusitis, orbital cellulitis). The breakthrough of infection is fraught with the development of meningitis and the formation of brain abscesses.
• Portal vein: Inflammation with thrombosis in this area is called pylephlebitis. The process is initiated by severe infections of the abdominal cavity and small pelvis. Septic masses from the portal vein system are carried directly into the liver, causing multiple hepatic abscesses.

Chronic local consequences

In situations where the thrombus does not fragment but obstructs the vessel lumen, a chronic violation of venous outflow develops. The acute period is accompanied by pronounced local tissue edema distal to the occlusion site, cyanosis, skin redness (if phlebitis is present), and compensatory dilation of superficial veins.

With a prolonged course, the process transitions into the stage of chronic venous insufficiency. Constant blood stasis leads to deep tissue hypoxia and microcirculation disorders. Morphologically, this culminates in necrosis of the superficial skin layers with the formation of severe, difficult-to-treat trophic ulcers on the lower extremities. In addition, the inflammatory-thrombotic process can acquire a recurrent character, successively affecting various areas of the venous bed (migratory thrombophlebitis).

Class and exam questions

What else to study on this topic

• Morphological signs of acute local venous congestion (cyanosis, edema, venous dilation).
• Chronic heart failure as a systemic cause of phlebothrombosis.
• Migratory thrombophlebitis: features of recurrent multiple venous lesions.
• Virchow's triad: mechanisms of increased blood clotting, slowed blood flow, and endothelial damage.
• Pathogenesis of septic brain abscess formation in thrombosis of the dural venous sinuses.

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Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.