Constipation and Megacolon in Cats
A condition where the colon becomes dilated and loses the ability to contract effectively, causing severe constipation. Can be dietary, behavioral, or idiopathic. In severe cases, the colon becomes permanently damaged and requires surgical removal.
Last updated: 2026-05-10
Severity
moderate
When to Act
See Vet Soon
Symptoms & Signs
Straining in the litter box
Repeated, unproductive trips — often mistaken for urinary straining.
Hard, dry feces
Small, rock-hard stools or complete absence of bowel movements for days.
Decreased appetite
Cat eats less due to discomfort and abdominal fullness.
Vomiting
May occur with severe obstipation — the colon is so full it compresses the stomach.
Lethargy and hiding
Cat feels unwell from systemic absorption of colonic toxins.
Behavioral Changes to Watch For
Pets can't tell us what's wrong. These behavioral changes are often the first clues that something is wrong.
🐾 Litter box avoidance and distress
Cat associates the litter box with pain and may defecate outside the box or cry while attempting.
What You May Notice:
Your cat runs in and out of the litter box repeatedly, crying, and may produce tiny hard balls or nothing at all. You find stool in random places around the house.
Causes & Risk Factors
Causes
- •Idiopathic megacolon — most common form; degenerative neuromuscular dysfunction of the colon
- •Dietary — low-fiber diet, dehydration (dry food-only, low water intake)
- •Obstruction — pelvic fracture malunion (narrowing the pelvic canal), tumor, foreign body
- •Neurological — spinal cord disease (Manx cats with sacral deformity)
- •Metabolic — hypokalemia, hypercalcemia, hypothyroidism (rare in cats)
Risk Factors
- ⚠Middle-aged to older cats (idiopathic megacolon)
- ⚠Manx cats (sacral spinal deformity)
- ⚠Cats with a history of pelvic fractures
- ⚠Chronic dehydration (kidney disease, dry food-only diet)
- ⚠Obese, sedentary cats
How It's Diagnosed
- 1Physical examination — palpation of a large, firm, feces-filled colon
- 2Abdominal radiographs — massively distended colon filled with impacted feces
- 3Pelvic radiographs — assess for old fractures narrowing the pelvic canal
- 4Blood work — rule out metabolic causes (hypokalemia, hypercalcemia)
- 5Neurological examination in suspected spinal cases
Treatment Options
Medical Management and Enema
For acute obstipation — clearing the impacted colon.
Steps
- 1.Warm water enemas under sedation (never at home without sedation)
- 2.Manual fecal extraction under anesthesia for severe cases
- 3.Oral laxatives: lactulose (osmotic) and/or cisapride (prokinetic)
- 4.High-fiber diet or low-residue diet (depends on underlying cause)
Expected Outcome
Colon cleared of impacted feces within 24-48 hours.
Precautions
- !Never give phosphate enemas (Fleet) to cats — FATAL hyperphosphatemia
- !Enemas must be performed by a veterinarian
Long-Term Dietary and Medical Management
For cats with recurrent constipation to prevent obstipation episodes.
Steps
- 1.Increase water intake: canned food, water fountains, flavored water
- 2.Lactulose — oral osmotic laxative titrated to produce soft stools
- 3.Cisapride — prokinetic agent (stimulates colonic motility)
- 4.Psyllium husk fiber supplementation — for some cats
- 5.Regular weight monitoring and bowel movement tracking
Expected Outcome
Regular soft stools and prevention of obstipation crises.
Precautions
- !Dietary changes take time — don't change diet abruptly
- !Lactulose overdose causes diarrhea
Subtotal Colectomy (Surgical Removal of the Colon)
For cats with end-stage megacolon unresponsive to medical management.
Steps
- 1.Removal of 80-95% of the colon
- 2.The small intestine is attached to the remaining rectal stump
- 3.Hospitalization for 3-5 days post-operatively
- 4.Soft stool or diarrhea is expected for 1-3 months post-op as the small intestine adapts
Expected Outcome
Excellent long-term quality of life — most cats produce formed soft stools within 2-3 months.
Precautions
- !$3,000-$5,000
- !Temporary diarrhea is normal post-op
- !Perineal irritation from frequent soft stools
Common Medications Used
Prevention
- ✓Feed canned food to increase water intake
- ✓Provide multiple fresh water sources
- ✓Regular weight and bowel movement monitoring
- ✓Address litter box issues promptly
- ✓Treat underlying metabolic disease
When to See a Veterinarian
- ⚠️Cat straining in litter box without producing stool
- ⚠️No bowel movement for 3+ days
- ⚠️Vomiting + constipation together
- ⚠️Distended, painful abdomen
Frequently Asked Questions
Can I give my cat a human laxative for constipation?
Prognosis
Good with medical management for mild to moderate cases. Cats with true idiopathic megacolon often eventually require colectomy, which has excellent long-term outcomes.
References
- [1] ACVIM — Feline Constipation and Megacolon
- [2] JVIM — Subtotal Colectomy Outcomes
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