Coagulation thrombus

Thrombosis is the process of intravital, intravascular blood clotting (Nennstiel 2019). The coagulation thrombus represents the classic form of thrombosis in the veins (Nüllen 2014).

Thrombi are differentiated between a:

- Clotting thrombus, the so-called red thrombus with a smooth surface (Herold 2022), also known as "tail thrombus".

- septal thrombus, the so-called white thrombus

- mixed thrombus

This consists of a head part, the deposition thrombus, and a tail part, the coagulation thrombus (Schindler 2021).

The essential characteristics of a clot thrombus are:

- red thrombus with a smooth surface

- filling of the entire vessel lumen

- no firm adhesion (Herold 2022)

Due to solidification of the thrombus, it can shrink over time and parts can become detached (Nennstiel 2019). For this purpose, even a minimal movement - such as abdominal squeezing during defecation - is sufficient to dislodge parts of the thrombus (Riede 2009).

Thrombi in general are a major cause of morbidity and mortality in a variety of arterial and venous diseases (Kasper 2015).

The incidence of clot thrombus increases with age. However, no exact figures are available for the FRG. The incidence of deep vein thrombosis is 70 - 113 per 100,000 persons / year (Ludwig 2020).

The causes of thrombus formation are summarized in the Virchow triad:

• I. Disruption or alteration of the vessel wall.

These can be caused by e.g.

- trauma

- arteriosclerosis

- great mechanical stress

- ischemia

All of the above factors can lead to damage to the endothelium, resulting in a lack of antithrombogenic substances and thus thrombin formation (Nennstiel 2019).

• II. disturbance of hemodynamics

Disorders of hemodynamics include a:

- Slowing of blood flow due to, e.g.

- Compression of the vessels

- Enlargement of the vessels (e.g., in varices)

- increase of hematocrit

- Increase of the viscosity of the blood

- Obstruction of the lumen

- Vortex formation, especially at passage obstacles, vessel branches and aneurysms

- Acceleration of blood flow due to, for example, hypertension, in which platelets are pressed against the vessel wall (Nennstiel 2019)

• III. disturbance of the blood composition

Blood composition disorder may occur due to:

- Increase in platelet count due to, e.g.

- Neoplasia of the hematopoietic system. This may lead to increased platelet activation.

- Increase in cell count due to e.g.

- Decrease in serum. Increased blood viscosity may lead to slowing of flow.

- Neoplasms

- Paraneoplastic syndrome in e.g.

- metastatic carcinoma. In this case, the carcinoma itself produces increased procoagulant substances.

- Hereditary disorders, e.g.

- Factor V Leiden mutation

- Postoperative or after injuries

- In this case, there are more clotting factors than normal in the blood due to tissue damage (Nennstiel 2019).

- Medication due to e.g. anticonceptives

- During pregnancy (Nennstiel 2019).

Cause of clotting thrombus is a slowing or stagnation of blood within a vessel due to, for example, surgery in a blood void, tumor compression, or a vortex formation (Nennstiel 2019).

The stagnated blood gradually suffers from a lack of oxygen, which causes the affected blood and endothelial cells to undergo hypoxidosis. As a result of the hypoxidosis, platelets and endothelial cells release substances that promote coagulation. This in turn leads to activation of fibrin and thus to coagulation of the stagnated blood (Nennstiel 2019).

Clotting thrombi are usually found in venous vessels of a tissue or organ (Claus 2019).

In coagulation thrombi, spontaneous, clinically silent autolysis occurs predominantly. Approximately 20% of thrombi are inapparent, in 1/3 an ascension of the thrombosis occurs, which can be followed by pulmonary embolism (Ludwig 2020).

When coagulation thrombi become symptomatic, the following clinical picture presents:

- Swelling with circumferential enhancement (lateral difference of > 3 cm [Cissarek 2009]).

- hyperthermia

- tenderness

- Cyanosis (Claus 2019).

In addition to the physical examination (see below), the Wells score should be assessed (see below and below).

The gold standard of instrumental diagnostics is color duplex compression sonography. The D- dimers should also be determined, but they are not very specific (Cissarek 2009).

Physical examination:

Signs of deep vein thrombosis, the most common clinical manifestation of coagulation thrombus are:

- Homans sign.

There is pain in the calf on dorsiflexion.

- Meyer's sign

In this case, a pressure pain is found on the inner side of the tibial edge along the course of the anterior and posterior tibial vein (Cissarek 2009).

- Payr's sign (Claus 2019).

When forceful pressure is applied to the medial hollow of the foot, there is pain in the sole of the foot (Cissarek 2009).

The sensitivity of these signs is 60-90%, but only between 0-20% in patients with severe systemic disease (Linnemann 2023).

Wells- Score

In the Wells- Score, various clinical characteristics are assigned points to determine the probability of the presence of coagulation thrombi (Linnemann 2023).

For more details, see. Wells- Score.

Color duplex compression sonography

It represents the gold standard of examinations (Cissarek 2009). In most cases, the complete extension of the coagulation thrombus can be detected (Linnemann 2023).

CT venography

This type of examination requires i. v. application of iodine-containing contrast medium.

Coagulation thrombi of the iliac veins, inferior vena cava, and proximal femoral veins should be examined by CT- venography to determine the exact extent. The sensitivity is 95.9%, and the specificity is 95.2% (Linnemann 2023).

MR venography

This three-dimensional examination is used electively, such as in preparation for surgical or interventional procedures (Linnemann 2023).

Phlebography

Phlebography is now subordinate to sonography and other imaging techniques. It is only used for specific problems (Linnemann 2023).

- Determination of the D- dimers

However, the specificity is low (Cissarek 2009).

Microscopically, the coagulation thrombus represents a loose fibrin network with abundant intercalated erythrocytes and scattered leukocytes (Nennstiel 2019). The erythrocytes appear as an eosinophilic red homogeneous mass and are indistinguishable from each other. The entire lumen is thrombosed, but there is no connection to the vessel wall (Claus 2019).

- Risk of embolism due to lack of firm adhesion (Herold 2022).

- Anoxia of the tissue (Kasper 2015)

A coagulation thrombus can be removed surgically or interventional. Conservatively, there is the option of therapeutic anticoagulation with e.g. low molecular weight heparin for > 5 days (Cissarek 2009).

See also deep vein thrombosis of the lower extremity.

Follow-up

The 1st control examination should be performed in the first 5 - 21 days after the start of anticoagulation to check the medication and the local findings. Further controls are recommended after 3 or 6 months. A re-evaluation with a decision to stop anticoagulation or continue it for secondary prophylaxis should then be made (Linnemann 2023).

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