Anal vein thrombosis and haemorrhoidal thrombosis


A spontaneous coagulation of blood in the veins can also occur in the anal area. This is termed “thrombosis”. Thromboses in the anal region are completely harmless and are not comparable to thromboses in major blood vessels of the leg or arm, in the eye or in the brain. An anal thrombosis does not influence the other forms of thrombosis just mentioned, i.e. it does not endanger the patient.

The spontaneous coagulation in the veins causes a drainage malfunction. This causes the affected tissue to increase in size many times over and the skin covering the area stretches, causing pain.


No cause is known for the formation of thrombosis.


We distinguish between two kinds of thrombosis:

  1. The type termed “anal vein thrombosis” affects a venous plexus at the lower end of the anal canal, at the anocutaneous line. A knot forms – frequently painful – and can grow to roughly the size of a cherry.
  2. The haemorrhoidal thrombosis, on the other hand, forms from haemorrhoids. If a thrombosis occurs here, then the “sponge” enlarges to many times its original volume, pressing on the interior sphincter towards and as far as the exterior, causing painful swelling of the anal skin.

It is therefore important to consider the two types as distinct, since this is relevant for treatment.

In addition to examination and palpation with the finger, one should also perform a proctoscopy.


For treatment, one must be able to clearly distinguish between the two types:

  1. The anal vein thrombosis can be opened without difficulty: once the trapped blood is drained, the patient’s symptoms disappear.
  2. A haemorrhoidal thrombosis, on the other hand, should not be opened, since subsequent bleeding can be prolonged and thromboses re-occur. Even for pronounced cases, surgical intervention is pointless, since the body breaks down thromboses after 10 days in such a way that the tissue is reduced entirely back to its original size. Anyone who did not have enlarged haemorrhoids before this will not have them afterwards. This is an all-important fact. For if, as often happens, one surgically removes the thrombosis, one performs an unnecessary haemorrhoid removal operation. We are happy to prescribe ibuprofen 3x 600 mg daily if there are no contraindications. These thromboses are already smaller after 5–7 days. After 10–12 days, there is usually nothing left of the thrombosis.


After a while, our patients come back for a check-up, where we examine the anal region again, this time under good conditions. If the examination indicates illness is present, then the patient can be scheduled for conservative or surgical treatment. Both offer maximum safety for the sphincter.

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Tel.: +49 (40) 4686 398 0


Robert-Koch-Straße 36
20249 Hamburg (Eppendorf)

Last update: 05.06.2024


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