I went up to spend the day with Pie again at the University of Wisconsin veterinary hospital. He's doing well - no "episodes" but then he hasn't had that much to eat yet - but is shiny and sassy and very sweet - all the staff and students like him. He gets several walks a day outside in their sand/rubber pellet footing walking area, and the vet student who's in charge of him even brushes him. He's not happy about being confined to a stall the rest of the time - he tells me about it - and has taken to mischief like untying the rope that secures the IV hanger (which he isn't using) or figuring out how to pick up his water dish.
Today the senior vet and resident did some repeats of exams - ultrasounds and rectals - that were done yesterday - since his GI tract was much emptier, they wanted to verify that the nodules were still there, and not just fecal matter. They were still there - at least a half dozen that the vet could palpate just at the end of his reach when doing the rectal exam - there may or may not be more out of reach. Ultrasounds of this area are difficult at best - Pie is too big and his abdomen is too broad. At least one seemed to be attached to the outer surface of the colon. They also did an abdominal tap, to see if any abnormal cells (white cells or cells indicating certain types of cancer) showed up, and to also start cultures (which will take about 48 hours) to see if any bacteria show up. So far everything looks normal - there are no abnormal cells in his abdominal fluid, and his blood work is normal except for slightly elevated GGT enzymes.
The initial thoughts were that Pie might have bastard strangles - encapsulated strep inside his abdomen. The senior vet now thinks this isn't likely - his blood work, the fact he's not at all sick in that way and the lack of white cells in his abdominal tap make this less probable although it's still possible. He also clearly doesn't have certain types of cancers that tend to shed cells into the abdominal space. At this point we don't know what he has - he sure doesn't look or act like a horse with cancer of any type. We've done the non-invasive tests that can be done - x-rays won't help in this case due to the type of thing and the location. A biopsy isn't practical - the location is risky and the nodules tend to be very moveable. Opening him up for surgical examination isn't warranted at this time and would be very risky.
So we really don't know. They're going to keep increasing his hay and pellets over the next day or so - since he's already there - and see if he experiences another episode of colic pain - they can then take a closer look to see what's really happening. At this point we're taking things one day at a time - but then that's how Pie always takes things and I'm trying to emulate his good example.