External hemorrhoids occur when the blood vessels under the skin surrounding the anus become inflamed or swollen. The inflammation is often due to straining during bowel movements, childbirth, constipation or diarrhea. Thrombosed external hemorrhoids are a specific type of hemorrhoid that occur when the tissues are cut off from blood supply and a clot forms, according to QuickCare.org.
Pain
The pain of a thrombosed hemorrhoid is excruciating. The National Digestive Disease Information Clearinghouse explains that the thrombosed hemorrhoid will be swollen and hard. This can make passing stools even more painful. The swollen vein tissues are full of nerve endings, making the hemorrhoid a very sensitive area. The anus may burn, especially following a bowel movement. The Mayo Clinic recommends medical attention within the first 48 hours of the suspected development of a thrombosed hemorrhoid. Removing the hemorrhoid early can provide the most relief.
Itching
Most hemorrhoids itch. The National Digestive Diseases Information Clearinghouse explains that drainage of mucus or pus can lead to even more intense itching. The pain of a thrombosed hemorrhoid, however, may make the itching less noticeable.
Bleeding
Following a bowel movement there is likely to be bright red blood in the toilet from the anus. This is a result of the blood vessel being so swollen that any pressure can cause bleeding. Spots of blood on toilet paper after wiping or even in the underwear can be signs of a thrombosed hemorrhoid.
Appearance
When typical home remedies have little or no effect on the hemorrhoid, it is likely that the homorrhoid has become thrombosed. Examining the hemorrhoid will reveal that the mass is not red but instead may be blue, purple or even black from the swelling and clotting of blood.


