When there is a blood clot formation with external hemorrhoids it results in what is called thrombosed hemorrhoid.
The veins in the anus area get inflamed resulting in a lot of pain and itching.
In the case of external piles, cleaning the area is also difficult after passing stools.
In the case of internal hemorrhoids the veins inside the anal canal get inflamed.
Symptoms of thrombosed hemorrhoid are - pain in the rectum anus area, itching, formation of tender lumps near the anus, bleeding while passing stools, blood in the toilet tissue or in the toilet bowel.
The bleeding happens due to the rupturing of the veins.
Pressure on the veins in the rectum and anus region increase due to factors like pregnancy, strain for passing stools, constipation, diarrhea etc.
  These are considered to be some of the main reasons for thrombosed hemorrhoids.
The simplest form of treatment is the use of creams and gels available in the local drugstores.
In very rare cases people go through the surgical process called "banding" to get relief.
The most preferred treatment option is the natural cure because of the long-term relief.
Natural treatment for thrombosed hemorrhoid will depend on the severity of your problem.
In case the problem is mild in nature, then simple changes to your diet may be recommended along with a hot and cold compress.
In case your problem is moderate to severe in nature then you may have to go for a combination treatment.
This will involve diet changes along with herbs for correcting - constipation, clot formation, pain and inflammation.
You need to remember that natural treatment for thrombosed hemorrhoid will not produce overnight results.
However if you are persistent and determined then you will see good long-term results.