Thanks for your replies. Not a medical problem. A stubborn, control problem. It helps to know that others have had similar situations. I'll share this with his parents of course. We'll keep on working at it. This too, shall pass. (pun intended)
It sounds like he's had a lot of external baggage attached to a natural act that is rightly within his control. Pediatricians are well aware of the psychology behind toileting for children, which is as important--if not more so--than the physical issue of encopresis.
Yes, it's a control issue, but it's also a trust issue. Does he feel his boundaries are being respected? Is he pushing back because he is being pushed? I would urge you and your GS' parents not to label your GS's behaviour negatively, and certainly wouldn't punish it, as that will lead to further toilet avoidance and compound the issue.
And as to whether this is a medical issue, if he's having impacted fecal matter, I'm sorry, but it is. Long term continence issues can stem from persistent encopresis. The first line intervention here in Canada is to assist in passing the mass gently, then assisting in toileting comfortably (physically) by giving the child water soluble PEG laxatives over the counter for a designated period of time. Only a doctor can provide the appropriate path for your GS given his experience, so don't delay.
