Anal thrombus or “thrombotic hemorrhoid” is a common ailment that comes on suddenly. It arrives with acute pain and the appearance of a dark purplish lump just outside the anal opening. The lump may form immediately or appear overnight and varies in size from that of a pea to that of a walnut.
The formation of thrombus generally follows heavy lifting, spasms of coughing or sneezing, straining at stool, etc. It may also occur without any apparent provocation. It is caused by the breaking of a small vein with the escape of blood beneath the skin. The blood becomes clotted shortly after the lump forms. The extreme pain is due to pressure upon the superficial nerve endings. When or if it ruptures, there is almost immediate relief but with the relief comes the peril of having complications if the cause is not remedied. In cases of smaller thrombus, sometimes the bloodstream absorbs the clot so there is no rupture but the complications are just as probable.
Anal thrombus is often confused with actual hemmorhoids, but it is not a true or usual type hemorrhoid. The lump forms suddenly instead of gradually and is formed in the skin on the outside instead of protruding down from the inside, as in hemorrhoids. It is filled with a clot instead of small diseased functioning veins as in hemorrhoids. The recovery from the acute attack is rapid in thrombus, whereas in hemorrhoids the recovery – if any – is gradual. The formation of thrombus is a signal pointing to an underlying cause that will usually be found in the rectum. It is unwise to leave such a condition untreated with the hope that it will cure itself.