Etiology and Predilection Sites
The pathological process can affect virtually any venous bed in the human body, although clinical cases are distributed extremely unevenly. The vast majority of episodes—around 90 percent—occur in the lower extremities. In this anatomical region, the deep veins of the calf and the large iliofemoral venous segment are the primary targets.
A clinically significant, complex, and extremely dangerous localization is the involvement of the cerebral veins and intracranial venous sinuses. It is important to note that this variant of the pathology does not arise primarily; it is always secondary and develops as a severe complication of purulent-inflammatory diseases of head structures. Such primary causes include meningitis, inflammation of the middle ear (otitis media), purulent involvement of the mastoid process (mastoiditis), inflammation of the paranasal sinuses (sinusitis), and infectious processes in the soft tissues of the orbit.
In pathological anatomy, involvement of the portal vein system is designated separately as pylephlebitis. Its triggering mechanism is always infectious-inflammatory foci initially located in the abdominal cavity and pelvic organs.
Morphological Pattern of the Acute Process
On macroscopic examination, acute thrombophlebitis demonstrates a striking picture combining signs of active inflammation and marked venous congestion. Because the formed thrombus blocks the vessel lumen (occlusion occurs), adequate blood outflow becomes impossible. This inevitably leads to pronounced edema of the soft tissues located distal to the site of obstruction.
Skin in the affected area acquires a characteristic bluish tint—cyanosis develops. This symptom indicates a massive accumulation of deoxygenated venous blood. Superficial veins dilate compensatorily, attempting to take over part of the blocked blood flow. Directly above the inflamed vein, marked skin redness and other classic signs of local inflammation are observed.
Variants of the Disease Course
The disease is characterized by a variable course. Migrating thrombophlebitis deserves special attention—a specific condition in which inflammation of the venous wall and subsequent thrombosis are multiple in nature. In this form, foci constantly recur, spontaneously appearing in completely different parts of the venous bed.
If the acute process does not resolve, it transitions into a chronic form, inevitably leading to persistent microcirculatory impairment. The chronic course serves as a fundamental basis for the development of chronic venous insufficiency. The primary morphological manifestation of this condition is deep trophic ulcers. They form predominantly on the lower extremities due to prolonged tissue hypoxia and nutritional impairment.
Life-Threatening Complications
This pathology harbors two main threats to the patient's life, directly related to the detachment of thrombotic masses and their subsequent migration through the bloodstream:
- Generalization of the infectious process. If the thrombus is initially septic in nature, its detached fragments transform into circulating septic emboli. Carried by the bloodstream throughout the body, they settle in organs and cause the formation of secondary purulent foci. Most commonly, this leads to abscesses of the liver, brain, and other structures.
- Pulmonary embolism (PE). This is the most formidable complication of both thrombophlebitis and phlebothrombosis. A detached thrombus enters the right chambers of the heart and is subsequently ejected into the pulmonary trunk. The primary sources of such lethal emboli are the iliofemoral veins, pelvic venous plexuses, and deep calf veins.