I have, from a fairly young age (I think around 3) had on/off rectal bleeding. Diagnoses/suggestions included
-Don't be afraid to poop (Haven't heard that one since preschool).
-Eat more fiber/drink more water.
-Hemorrhoids, which brought us back to the previous.
By the time I was fourteen or fifteen, it was getting ridiculous. I would have bowel movements consisting of nothing but blood & mucus- I was taking 300% RDA of iron and was still mildly anemic. Yet all I heard was that I shouldn't strain as much and to eat more fruits and whole grains.
When I was 16, I went to a GI specialist who performed a colonoscopy on me and discovered that I have ulcerative colitis. Not hemorrhoids.
I suggest that any parent who gets a diagnosis for their child that doesn't seem to make sense take the kid to a specialist. My pediatrician had never had a patient with UC before; even though it can occur at any age, the peak diagnosis rates are from ages 15 through 35, an age group she didn't see very often.