bowel movements

My 9 year old son does not wipe himself properly, even though my husband and I trained him in this at a young age--and reinforced this as well.
However, now he is having full bowel movements in his underwear and leaving it in there for sometimes 6 hours at a time. We have talked with him about this, and his reasons include: laziness, can't make it in time, or fear of the toilet overflowing.
He does well in school with minor issues, such as talking, occasional hitting. He is disciplined by having priviledges taken away.
Should I take him to his pediatrician, or a psychologist?

[Kevin Kennedy, Ph.D.]

By all means first take him to the pediatrician. The rule of thumb is always to rule out any medical condition before investigating emotionally-based or psychological explanations.