Etiopathogenesis: Virchow's triad
The formation of an intravascular thrombus is caused by three classical pathophysiological mechanisms. These risk factors can occur either in isolation or in combination, mutually worsening the prognosis.
- Slowed blood flow (stasis). It occurs in individuals with a sedentary lifestyle. It is often triggered by prolonged bed rest (e.g., in the postoperative period or after a myocardial infarction), and is also common in the postpartum period. Additional triggers of stasis include heart failure, various arrhythmias, obesity, the presence of varicose veins, and a history of DVT episodes.
- Vascular wall injury. Endothelial dysfunction and direct damage to the integrity of the venous intima most commonly occur against the background of mechanical trauma and bone fractures.
- Increased blood coagulability (hypercoagulability). Changes in the rheological properties of blood are characteristic of oncological diseases (acting as a paraneoplastic syndrome), polycythemia, as well as pregnancy and the use of oral contraceptives.
Clinical forms of the disease
The symptoms of deep vein thrombosis are extremely variable. In clinical practice, it is customary to distinguish two main forms of the disease course, which require high vigilance from the physician.
- Mild/subclinical form. The most insidious variant, which is often observed in inpatient (bedridden) patients. Local symptoms may be completely absent. Indirect signs allow suspecting a critical condition: a slight, but unexplained deterioration in the patient's general condition, sudden onset of tachycardia, and an increase in body temperature to subfebrile values.
- Classic form. Characterized by prominent subjective complaints. Patients note a pronounced feeling of heaviness in the legs and intense, bursting pain in the affected limb.
Physical and differential diagnostics
Physical examination plays a crucial role in establishing a provisional diagnosis.
Visual assessment reveals an increase in lower leg volume and pronounced edema on the affected side. The most important objective method is anthropometry. The physician must measure the circumference of the lower legs with a tape measure at strictly symmetrical levels. A reliable diagnostic criterion is a unilateral increase in volume, especially if it progresses dynamically.
Upon palpation, the affected limb feels warmer than the healthy one. If the thrombotic process extends high (involving the femoral or iliac vein), palpation causes severe tissue tension and noticeably worsens the patient's general condition. A specific sign is the appearance or sharp increase of pain in the calf muscle upon forced dorsiflexion of the foot.
The clinical picture of deep vein thrombosis is nonspecific. When performing differential diagnosis, it is first necessary to exclude soft tissue hematoma and partial tear of the calf muscle, which can produce similar local symptoms.
Association with varicose veins
Varicose veins are one of the risk factors for blood stasis. They are characterized by a specific picture: patients complain of discomfort and rapid leg fatigue when walking, while the condition noticeably improves at rest, especially if the limbs are elevated.
The golden rule of phlebology: inspection and palpation of varicose veins must be performed exclusively while the patient is standing. This is the only way to achieve adequate gravitational blood filling of the vessels. In chronic cases, varicose veins lead to severe complications: initially, stasis eczema develops, which is a direct precursor to the formation of trophic ulcers.
Briefly: answers to topical questions
What is the name of the sign characterized by pain in the calf muscle upon forced dorsiflexion of the foot?
The sign characterized by pain in the calf muscle upon forced dorsiflexion of the foot is called Homans' sign. This finding is detected during the physical examination of patients with suspected lower extremity deep vein thrombosis. This eponymous sign is elicited by palpation and specific maneuvers, although it is not strictly pathognomonic for this disease, despite allowing one to suspect the development of thrombosis.
What pathologies should be differentiated from lower extremity deep vein thrombosis?
Differential diagnosis of lower extremity deep vein thrombosis is carried out with conditions whose clinical picture can mimic it:
- hematoma;
- partial tear of the calf muscle.
What instrumental and laboratory research methods are used to confirm the diagnosis of deep vein thrombosis?
The cited sources indicate the following instrumental methods for the diagnosis and verification of deep vein thrombosis:
- Lower extremity duplex ultrasound: compression angioscan, duplex and/or triplex scanning; the highest diagnostic value is indicated for B-mode with vein compression every 2 cm.
- When iliocaval thrombosis is detected and its proximal boundary cannot be accurately determined by ultrasound: contrast-enhanced MDCT or contrast-enhanced MRI of the lower extremity; the goal is to determine the boundaries of thrombosis and verify competing conditions.
- In planned surgical thrombectomy and/or vena cava filter implantation in patients with iliocaval thrombosis: inferior vena cava phlebography for primary verification of venous thrombosis prior to intervention. Phlebography is not recommended for routine primary verification of venous thrombosis.
Laboratory methods for confirming the diagnosis of DVT are not specified in the cited sources.
Virchow's triad: three "S" — Stasis, Surface (injury), Sanguination (hypercoagulability).
What else to study on this topic
- Pathogenesis of paraneoplastic syndrome formation in oncological diseases
- Features of the course of thrombosis in the postpartum period
- Mechanisms of transition from stasis eczema to a trophic ulcer
- Clinical differences between DVT and hematoma and calf muscle tear
- Effect of oral contraceptives on blood rheological properties
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