Embolisation – a misguided approach in venous compression syndromes
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Embolisation of dilated veins in compression syndromes

When the return of venous blood to the heart is disrupted, the affected veins expand. One reason for such a dilatation can be the compression of a vein. The venous blood then accumulates in front of the flow obstruction. Inside the distended vein an elevated blood pressure builds up, which leads to a slowing down of the blood flow in front of the obstacle. At the obstacle itself there is a strongly accelerated blood flow. The situation is comparable to that of a reservoir. In the reservoir the river stagnates, at the dam the current rushes strongly accelerated across the obstacle as in a cascade.

In the case of venous compression syndromes, a high pressure build-up therefore occurs on the side of compression facing away from the heart. This causes the vein to expand like a reservoir. This stretching is very painful. The slowing down of the blood flow can become so severe that no normal bloodflow can be maintained. This is accompanied by an increased risk for developing thromboses in the congested vein. From there embolisms can spread, usually as pulmonary embolism, in some cases also as stroke.

When the congestion pressure reaches a certain level, the blood flow from the periphery must find new routes back to the heart. It starts flowing through smaller veins, collateral veins. Normally, the congested vein receives blood from these smaller veins. Due to the congestion, however, the pressure in the receiving vein increases so much that the blood now flows back into the smaller veins. This means that the organs from which the blood comes are now flooded with additional venous blood instead of relieving themselves from their own venous blood. This causes severe pain in the affected organs. In the pelvis these are usually the left ovary and the uterus, often also the vagina and rectum, in men the prostate.

These so-called midline organs now take up the blood from the congested iliac vein and drain it to the right side. For this purpose, blood flows backwards from the left pelvic vein via the smaller organ veins into the affected midline organs, backwards through these organs, to the right side of these organs and from there into the right-sided pelvic veins.

This situation is called pelvic congestion syndrome.

During the examination of affected patients, severely dilated veins in the pelvis, in the perineal area, in the inner and outer genitals or in the rectum (haemorrhoids) are often detected. Particularly eye-catching is the dilatation of the left ovarian vein/testicular vein (Vena ovarica sinistra/Vena spermatica sinistra), which is associated with grossly dilated veins in and around the uterus or prostate.

As these veins are very painful during the examination of the patients, it is now not rarely recommended to get rid of these veins.

This recommendation is made under the idea that the interruption of the blood flow in these congested veins should relieve the pain.

Patients are therefore advised to embolize these veins by means of a catheter inserted via peripheral veins, usually from the groin area. For this purpose, the left ovarian vein, and numerous veins around the uterus, and the right ovarian vein, are obstructed with wire coils. This procedure is called embolization or coiling.

Unfortunately, these measures often have only short and limited success. When planning the procedure, it is often completely ignored why the veins that are to be embolized are dilated. It is claimed, without any further diagnosis, that the veins are flaccid and that therefore the blood in them becomes engorged or refluxes.

In many cases, however, these veins are dilated because the blood cannot leave them. It may say in front of an obstacle, for example the sacral bone or the spine. On the other hand, however, a large amount of blood may have been diverted from other organs into the congested vein, thus overloading its transport capacity. This is regularly observed in the so-called nutcracker phenomenon of the left renal vein.

As the diagnosis of the nutcracker phenomenon is challenging,  it is often missed. It is not uncommon for the diagnosis to be denied, even though a specific search was made for it! However, the methods used for this purpose, computer tomography and magnetic resonance imaging merely depict the dilated veins but tell littel to nothing  about the direction of blood flow and the pressure in the veins. In addition, it requires special experience and many years of study of vascular compression syndromes in order to detect the nutcracker phenomenon with the standard procedures of radiology in every patient.

If it is not recognized that the congestion due to a volume overload is caused by the nutcracker phenomenon or by an increase in pressure due to the impeded outflow of blood from the pelvis, then there is a very high risk of embolisation.

The embolization of the dilated veins then regularly aggravates the existing symptoms. In most cases, a short-term relief of symptoms can be observed after the procedure, which after a few weeks or months leads to an increase in pain beyond the level existing before the procedure. This is due to the fact that the intervention initially causes the blood pressure  to drop inside the formerly congested veins. The lack of stretching of the now embolized veins is accompanied by a reduction in pain. However, since the cause of the dilatation of the veins has not been identified, a high pressure remains in the left renal vein or in the left pelvic vein. This high pressure is pushing blood into new collateral veins, as the embolisation closed the existing bypasses. After their removal, the blood from the congested veins must now be transported to the heart via even smaller veins than before. Since the unchanged very high blood volume is now forced through even narrower vessels, these again expand very strongly. Therefore, after a short interval of pain reduction, unbearable pain often occurs in the same regions as before the embolisation and additionally in other areas where new collaterals are now developing.

Therefore, it is not advisable to embolize dilated veins in the abdominal and pelvic area until vascular compression syndromes have been ruled out with certainty.

The suitable procedure in such cases is the precise visualization of the blood flow in all veins of the abdominal and pelvic area, if necessary also in the genital region, the back, the legs and other parts of the body with the aim of measuring the blood volumes in the main veins and their collaterals. This is the only way to ensure that an intervention is successful.

 

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