Thank you for your question.
I am Dr. Su S. and I will try my best to help you.
Fresh blood on wiping comes more likely from the lower part of the bowel near anus or rectum.
The common cause of bleeding is from a trauma or a tear in anal margin.
The other causes are from polyp, an inflammation or infection.
In constipation there can be fissure.
In infection stool usually frequent and loose.
Small amount of blood is usually not worrying & is often from trauma in this age.
However, an examination by doctor needs to be taken.
He can take a few tests after the examination.
Please try to give more fluid.
I hope this information will be helpful.
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Wish his healthy life.