"External haemorrhoids"
If you feel a - usually - painful lump at the anus, which is bluish in colour and has developed overnight, you may think of a haemorrhoidal condition. However, another condition is also a possibility: the reason for your discomfort could be anal thrombosis. But don't worry, unlike deep vein thrombosis (DVT), this vascular blockage is not threatening because the clotted blood cannot be washed into other vessels (embolism). In many cases, treatment is not even necessary and waiting and observing may already be the best therapy.
Read also the interview by Bild der Frau reporter Gabriele Eisenrieder with Dr Hofer.
In the subcutis around the anus there is a network of fine veins (plexus haemorrhoidalis externus). The name is misleading, these vessels have nothing to do with the real (internal) haemorrhoids. They divert oxygen-poor (dark red to blue) blood via the iliac vein (V. iliaca interna) into the inferior vena cava, which leads through the abdomen and thorax to the heart.
Even under normal conditions, blood flows in these vessels at a low pressure of about 15 mm Hg. Any compression or increase in pressure in the abdomen causes the blood flow in one of these vessels to stop. The vessel swells and the blood it contains clots - anal vein thrombosis has developed.
This explains most of the risk factors or triggers of such events of anal thrombosis:
Other triggering factors are
Pregnancy combines several risk factors: Hormonal changes lead to constipation in many women. The baby and amniotic fluid put pressure on the intestines and the pelvic floor. The body's water content increases steadily towards the delivery date, and the connective tissue becomes more stretchy. The general tendency to thrombosis also increases.
When pushing during birth, the pressure in the anal veins increases again. The passage of the baby leads to tears in the pelvic floor muscles, the resulting bruise sags to the lowest point. In postpartum women it is therefore not uncommon to find swelling around the anus, sometimes considerable ("cauliflower-like"), which is misunderstood as 4th degree haemorrhoids. Clinically, a mixed picture of anal thrombosis, swelling due to water retention (oedema) and haematoma is seen.
Some patients report non-specific precursors of symptoms (prodromes) one to two days before the onset of anal thrombosis, such as mild itching or tingling. Anal thrombosis manifests itself as sudden pain and a palpable bulge at the edge of the anus. Burning and stinging are also possible symptoms.
Anal vein thrombosis can be recognised by a bluish-black lump covered with shiny stretched skin. This feature helps the doctor diagnose anal venous thrombosis and rule out other conditions such as haemorrhoidal disease: The surface of haemorrhoids has the slightly granular or velvety texture of the transitional or intestinal mucosa. On simple palpation, a bulging, smooth-bordered lump that is displaceable relative to the surrounding area can be felt.
The size of an anal vein thrombosis can range from pinhead to plum-sized. Not infrequently one finds not only one, but several knots.
Good medical care consists in doing nothing as much as possible. (Samuel Shem 1978, The House of God)
The good news is that anal venous thrombosis often heals on its own within a few days to weeks. So the essential part of treatment is to take away the pain until the body has healed itself. Furthermore, there are some tips to keep in mind so that the thrombosis knot does not expand any further. And last but not least, the diagnosis must be confirmed before you sit back and wait.