Megacolon in cats: medical management with lactulose and cisapride
8-year-old overweight neutered male domestic shorthair cat with a third episode of constipation in a year. After deobstipation, the colon remains dilated but retains some motility. There is no pelvic narrowing and no neurological signs.
What is the basis of long-term medical management?
chevron_right Show answer and explanation
A. Lactulose titrated to soft faeces, cisapride as a colonic prokinetic, good hydration (wet food) and adjusted fibre
Correct. Lactulose retains water in the colonic lumen and cisapride (a 5-HT4 agonist, compounded where needed) stimulates colonic smooth muscle. They work while some motility remains; hydration is essential.
B. Metoclopramide as a colonic prokinetic
Metoclopramide acts on the stomach and proximal small intestine and has little effect on the colon.
C. Daily oral liquid paraffin as a maintenance laxative
It is tasteless and easily aspirated in cats, causing lipoid pneumonia. It also interferes with absorption of fat-soluble vitamins.
D. Weekly preventive phosphate enemas
Phosphate enemas are toxic in cats and must never be used.
lightbulb Key takeaway
Feline idiopathic megacolon is a dysfunction of colonic smooth muscle. While motility persists, medical management works; when the cat keeps becoming obstipated despite it, subtotal colectomy is the treatment of choice.
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.