Brief Answer:
Hemorrhoids are the most probable reason.

Detailed Answer:
Hello!

Thank you for the query.

At your age, we do not suspect anything serious. If the blood was on the surface of the stool, not mixed with it, hemorrhoids or rectal fissure are the most common reasons of such symptom.
Hemorrhoids can be missed with rectal examination. Its because when you stick a finger inside rectum, hemorrhoids collapse so can not be palpated. Itching around anus is quite characteristic for hemorrhoids as well.
Rectal fissure gives strong pain when passing stool.
Both conditions are caused by hard stool and constipation.

If you get blood mixed with stool, or a lot of blood in toilet so the water gets red, inflammatory bowels disease or bacterial infection can be the reason. Both case should give diarrhea and abdominal pain.

I suggest you to follow this steps and see if it will help:
- start fiber and probiotic supplementation
- drink plenty of mineral water
- do not push hard on stool
- wash your rectum after every stool
- have sitz baths with Oak Bark twice a day for 5 days
- have OTC suppositories for hemorrhoids for 7 days

This should help in a week or so. If not, you should consult gastrologist and consider colonoscopy.

Hope this will help. Feel free to ask further questions.
Regards.

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Brief Answer:
Hemorrhoids are still most probable.

Detailed Answer:
Well, this makes hemorrhoids still most probable. They can sometimes bleed for that long.
Please follow as advised above.

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Brief Answer:
Colonoscopy is not necessary at this point

Detailed Answer:
No, its too early for colonoscopy. You are too young to have any serious problems in large intestine. Try fiber and suppositories first.

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