Back to square one (almost)

I thought we were making progress last week, as Derry was doing well until last evening when he started having diarrhea again.
 
His blood work and fecal tests were great, save for above-high normal sodium levels (dehydration, presumably due to the diarrhea he'd been having plus all the water-absorbing additives I'd been giving him).
 
Since there was absolutely nothing in the results to indicate a reason for the sudden onset, I have to assume it's food/ingredient related.

I've recently been trying a few brands of hairball kibble*, added to his usual Orijen, to see if anything would help; maybe that's inflamed his gastrointestinal tract. It used to be Nicki who had such a sensitive system, not Derry.

I've got an email into my vet about a gastrointestinal/fibre dry food, since I can't get him to eat the canned, any needed meds, etc. and will pop over later to pick up whatever is prescribed.
 
I actually wish there had been something in the fecal test, something easily treatable, because sorting out a food issue can be difficult, as I know from my own personal experience!
 
So we're almost back to square one. The test results do rule out a slew of dire possibilities, which is a relief, unless something was missed at the vet's end regarding testing.

Anyway, one step at a time and all that. Comments are off today; I just wanted to give an update, since everyone has been so kind. Thanks for your care and concern and I'll do another update at some point, hopefully with better news.

 
*He had no problems until a couple of weeks (maybe less) after I started adding in one brand in particular; I wonder if that was the trigger.