Diagnosis of a calf thrombosis
The calf thrombosis can become noticeable in various ways. For example, a physical examination with calf compression pain (Meyer’s sign), calf pain when the toes are pulled towards the shin (Homans sign) or sole pain when pressure is applied to the sole of the foot (Payr sign) can provide indications of the presence of a calf thrombosis. However, these signs are not very reliable.
Therefore, an ultrasound of the leg veins and a blood sample should be taken. Whether the blood sample or the ultrasound is taken first depends on how likely the presence of a calf thrombosis is. This is determined by the Wells Score, which classifies the probability of the presence of a venous thrombosis.
This includes, for example, an anamnesis, whereby the question is asked whether a calf thrombosis has ever occurred. Immobilization (bed rest or paralysis) is also taken into account. Furthermore, each symptom on the leg is assigned a point (e.g. edema, difference in circumference of > 3cm compared to the opposite side, etc.).
If the score is greater than or equal to 2, a calf thrombosis is likely and an ultrasound of the leg veins should be performed immediately. Ultrasound of the veins – or compression sonography of the leg veins – is the method of choice if thrombosis is suspected. In this procedure, the veins are followed from the pelvis to the feet using ultrasound and pressure is applied to the veins, which cannot be compressed if thrombosis is present.
With this procedure, thrombosis can be quickly and reliably ruled out or detected without radiation exposure. The only disadvantage of this method is that the examining physician must be familiar with the procedure or must be practiced in it – compression sonography therefore also depends on the investigator’s expertise. Phlebography is an X-ray procedure in which the veins are visualized using a contrast medium.The contrast medium is injected into the superficial veins before the X-ray and serves to improve their visualization.
Thrombi can be reliably visualized if they are present. However, since this is a procedure involving radiation and there is a certain risk of side effects when injecting the contrast medium, sonography is preferred for diagnostic purposes in cases of suspected calf thrombosis. If, however, there is a suspicion of a vessel in the pelvic region being blocked, phlebography is indicated, as it also allows the supply of surrounding organs in the pelvis to be assessed.
Particularly if a calf thrombosis is rather unlikely but still cannot be excluded with certainty, a blood sample must be taken with the following blood test. This can lead to an increase in the blood sedimentation rate (BSG) and possibly to an increase in white blood cells (leukocytosis). Furthermore, the so-called D-dimers are determined.
D-dimers are cleavage products that are formed during the formation of a blood clot. A normal value almost completely rules out thrombosis. However, an increase in the value may not only occur in the case of thrombosis but also have other causes such as a tumor or even after an operation.
Therefore, if the D-dimer value is increased, a compression ultrasound of the veins should always be performed. In coagulation diagnostics – also known as thrombophilia diagnostics – a check is made after the indication is established to determine whether coagulation is functioning properly or whether there is too much or too little of certain proteins. Indications are, for example, previous thromboses or thromboses that have occurred in a family.
The basic diagnostics then includes the determination of the activity of protein S and C as well as antithrombin, all three of which serve to inhibit clotting and which cannot sufficiently counteract the formation of clots if their activity is reduced. Furthermore, the APC resistance is determined. This results in the resistance of coagulation factor V to activated protein C. This means that protein C cannot inhibit factor V and an increased clot formation and thrombosis tendency occurs.
In addition, the coagulation speed is checked using Quick and aPTT. If there are any abnormalities in the blood test, further data are checked. This topic may also be of interest to you: Protein C Deficiency
