Rindy, I found the following two articles on the web. Most of the other entries were for cats.
Q: Dear Dr. Mike, My brother has a springer spaniel that has been diagnosed with megacolon. He has taken the dog to many vets and even to Michigan State University for treatment. The best treatment he has been able to come up with is a daily enema. Why is this ailment so different in dogs than in cats? And, as always we are looking for any new cures or ideas on cures that we can get. Any information that you have on this ailment would certainly be helpful as well as any suggestions for cure. Thank you in advance for your time and consideration. Matthew
A: Matthew- Megacolon is very different in dog than it is in cats. I am not able to explain the differences because I don't really understand why the problem occurs in cats or in dogs unless there is an obvious cause like an obstruction, tumor, etc. Someone probably can explain this but if so, I haven't found a really clear explanation in any texts I have!
Anyway, the major difference in treatment is the general success of surgery for this condition in cats and the lack of success for surgical correction in dogs.
Cisapride (Propulsid Rx) has been recommended for this condition but I have seen articles saying it should not be used or is ineffective, too. Personally, I'd be hard pressed not to try it if I was treating a dog with this condition because there are few alternatives. There may be benefits from using ranitidine (Zantac Rx) or nizatidine (Axid Rx) may help with this by increasing intestinal mobility, according to information posted on the Veterinary Information Network. These were the only two medications of this type mentioned (famotidine, Pepcid Rx, and cimetidine, Tagamet Rx are other medications in this this group of "H2" blockers but the post suggested that the Zantac and Axid may be the only ones with this effect.
I know this isn't much help. You have worked hard to get good advice and I wish there was more to give.
Mike Richards, DVM
J Small Anim Pract 2008,Dec,01;49(12):618-24; (PMID: 18793255)
Nemeth, T ; Solymosi, N ; Balka, G;
The Journal of small animal practice (ISSN: 0022-4510)
OBJECTIVES: To evaluate the long-term results of subtotal colectomy for acquired hypertrophic megacolon in the dog. METHODS: Eight dogs with acquired hypertrophic megacolon underwent subtotal colectomy with preservation of the ileocolic junction. Long-term follow-up was obtained by clinical records and telephone interviews with the owners. RESULTS: Eight large-breed dogs (age range: 6 to 12 years; mean age: 10.75 years) were enrolled. The use of bone meal, low levels of exercise, chronic constipation with dyschesia and tenesmus refractory to medical management were factors predisposing dogs to acquired hypertrophic megacolon. The diagnosis was confirmed in all animals by abdominal palpation, plain radiography and postoperative histopathological findings. There were no intraoperative complications. One dog died as a result of septic peritonitis. The clinical conditions (that is, resolution of obstipation and stool consistency) of the remaining seven dogs were improved at discharge; all animals returned to normal defecation in five to 10 weeks (mean: 7.3 weeks) and were alive 11 to 48 months (mean: 40.5 months) after surgery. CLINICAL SIGNIFICANCE: Predominantly bony diet and/or low levels of physical activity may predispose dogs to acquired hypertrophic megacolon. Our results emphasise the long-term effectiveness of subtotal colectomy with preservation of the ileocolic junction in this condition.
Ya'll drive safe and come back soon.