Thal notes several concerns and questions inherent in accurately diagnosing and effectively treating colitis.
1. Protein loss is massive. Huge quantities of plasma and synthetic colloids such as hetastarch are needed to keep pace with protein loss.
2. Massive fluid and electrolyte loss occur. It takes huge volumes of intravenous crystalloid fluids to keep pace with these losses.
3. Laminitis may occur secondary to the GI disease. "Just when you think the colitis has taken a turn for the better, laminitis can start," says Thal. "Cold should be the best
prophylaxis in these cases, but is difficult to do well. I know it's controversial and probably refuted by now, but I still
use nitroglycerin topically."
4. Thrombosis can occur. Because catheters are necessary to administer intravenous supplementation, a horse's jugular vein and any place that had a
catheter may develop thrombosis. The animal may suffer disseminated intravascular coagulation in which anti-clotting factors
(e.g., the protein antithrombin III) are lost in great quantity, leading to spontaneous clotting. Another thing to consider
is the effect of gram-negative endotoxin on the endothelial cells, which sets up a hyperinflammatory, hypercoagulable state,
so the animals end up in thrombosis. "Once a catheter site starts to go, it's usually over for the vein," says Thal. "One
horse I sent home lost two major veins—one lateral thoracic and one jugular. A lot of them go home with at least one thrombosis.
These are the typical challenges we face in treating these horses."
5. Identifying an agent is extremely difficult in many cases. Even with PCR panels, there are many cases that go undiagnosed.
6. Should you use systemic antibiotics or not? Since the GI flora can be tricky, determining the best regimen is critical.
7. Are probiotics useful? "This would include 'transfaunation' with filtered manure from a healthy horse," says Thal (see below for more).
8. Should you prescribe NSAIDs? They may seem necessary, but studies have shown adverse effects on GI healing that must be considered.
9. Do intestinal protectants and antidiarrheals work? Examples include di-tri-octahedral smectite (Bio-Sponge—Platinum Performance) and bismuth subsalicylate. But how helpful
are these treatments it in these cases?