Sudden lumps or swellings are usually caused by an anal vein thrombosis. These knots can not be pushed back permanently into the anal canal, but they return again to the outside. They are, that is to say, developed outside. Also an abscess causes a swelling, in the process the pain increases significantly. In this case must be acted quickly. Very large haemorrhoids may prolapsed, and cause pain. Also perianal skin folds (skin tags) may occur as nodes.