FRIDAY MORNING UPDATE: No call from the vet last night, which is good news. They'd have let me know if Aaruba had turned for the worse. That's all I know at the moment...thanks so much for all your messages of hope and support. Keep jingling!
Aaruba is in the hospital. We checked him in at 11:00 last night with mild, persistent colic symptoms that reminded me too much of his near-fatal impaction in October 2007. Everything is the same this time, only we caught it sooner, and he's not improving at the same rate as before.
He appears to have a small intestine impaction, which my vet tells me is unusual in our area. Even more unusual is the fact that his heart rate is normal (32 bpm) and his pain is mild. He's passed some manure, but he also refluxed 4 gallons a couple hours ago. Surgery is not an option due to poor prognosis for success, given his history. Everything points to some kind of flaw in his intestine, an adhesion or similar, that has persisted for years now and causes occasional, serious problems. Even if he makes it through this time, the underlying issue will remain.
All we can do is keep him on IV fluids and try a drug to enhance intestinal motility. Typically, the drug is contraindicated in cases where an impaction already exists, and you probably wouldn't want it in a horse that might go to surgery, but we're running out of options. I'll be honest with you: this looks very bad.
As they say on the Chronicle of the Horse forums, start jingling.