When the Colon Struggles to Keep Moving
Constipation is far more common in older cats than most owners realise, and it is considerably more serious than the occasional missed litter box visit might suggest. A cat straining without producing faeces, passing very hard and dry stools, or crying out whilst attempting to defecate is experiencing genuine discomfort. Left unaddressed, constipation can escalate into obstipation — complete inability to pass stool — and ultimately megacolon, a condition involving permanent colonic dilation that can require surgery or prove fatal.
Understanding why older cats become constipated, and acting early, makes an enormous difference to their quality of life and long-term prognosis.
Common Causes in Senior Cats
Dehydration sits at the root of most feline constipation. Cats evolved as desert animals with a naturally low thirst drive, and many drink far too little water relative to their needs. This becomes increasingly problematic as cats age, particularly if they are fed primarily dry kibble. The colon's job is to reabsorb water from digested material, and when a cat is already dehydrated, this process extracts so much fluid from faecal matter that the result is rock-hard, immovable stool.
Arthritis is another underappreciated contributor. A cat with painful hips or a sore spine may find the squatting position required to defecate genuinely uncomfortable, leading to avoidance behaviour that compounds the problem. Similarly, an arthritic cat may struggle to climb into a litter tray with high sides, making litter box aversion a pain-related rather than a behavioural issue.
Pelvic injuries from road accidents or falls earlier in life can leave narrowed pelvic canals that make faecal passage difficult. Neurological problems, including spinal disease and diabetic neuropathy, impair the nerve signals that coordinate colonic movement. Kidney disease, hyperthyroidism, and hypokalaemia (low potassium) can all alter intestinal motility. Certain medications, including opioids and some antihistamines, are constipating by nature.
Obesity and sedentary lifestyles reduce overall gut motility, and anxiety or disruption in the home environment can cause cats to suppress the urge to defecate for extended periods. Hair accumulation in the colon — particularly in long-haired breeds or cats experiencing excessive shedding — physically obstructs passage.
Recognising Constipation Early
The most important habit a cat owner can develop is knowing their cat's normal defecation frequency. Most cats defecate once to twice daily. A cat who goes more than 48 hours without producing stool warrants attention. Signs to watch for include:
- Repeated visits to the litter tray with little or no result
- Vocalising or straining during attempts to defecate
- Small, hard, dry stools that may be coated in mucus or small amounts of blood
- Reduced appetite and lethargy
- Occasional vomiting — often confused with hairball activity
- A distended or firm abdomen
One critical point: straining in a litter tray can indicate urinary blockage rather than constipation, particularly in male cats. Urinary obstruction is a life-threatening emergency. Any cat who has not passed urine for more than a few hours and is straining must be seen by a vet immediately.
The Progression to Megacolon
When constipation is recurrent or goes untreated, the colon progressively stretches to accommodate the accumulating faecal mass. Over time, the smooth muscle of the colonic wall loses its ability to contract effectively. This permanent dilation and loss of function is megacolon.
Idiopathic megacolon — where no underlying cause can be identified — accounts for the majority of cases and is thought to involve an intrinsic defect in colonic smooth muscle. Cats with megacolon often require manual disimpaction under general anaesthesia to remove the faecal mass, followed by long-term medical management. When medical management fails, a surgical procedure called subtotal colectomy — removal of most of the colon — can significantly improve quality of life, with most cats adapting well to producing softer, more frequent stools post-operatively.
Treatment and Management Strategies
For straightforward constipation, treatment typically begins with increasing hydration. Switching to a wet food diet or adding water or low-sodium broth to meals is among the simplest and most effective interventions. Cat water fountains encourage drinking in many cats who ignore still water bowls.
Lactulose is a synthetic sugar that draws water into the colon by osmosis, softening stool and stimulating movement. It is safe for long-term use in cats and available as a syrup that can be added to food. Polyethylene glycol (PEG 3350) is similarly effective and generally well tolerated. Stool softeners such as docusate sodium are sometimes used but have a weaker evidence base in cats than lactulose.
Cisapride, a prokinetic drug that stimulates colonic contractions, is often used in cats with recurrent constipation or megacolon. It requires a veterinary prescription and is not universally available, but where accessible it is highly effective.
Dietary fibre can help some cats and worsen others — soluble fibre adds bulk and stimulates motility, but too much insoluble fibre in a dehydrated cat can make stool harder. If fibre supplementation is considered, psyllium husk in small amounts mixed with wet food is a reasonable starting point.
Addressing underlying causes is essential. Pain management for arthritis, litter tray modifications for mobility-impaired cats, weight loss programmes for obese cats, and reviewing all current medications for constipating effects should all be part of the approach.
Preventing Recurrence
Senior cats with a history of constipation need a long-term management plan rather than occasional crisis intervention. Regular monitoring of defecation habits, consistent hydration support, appropriate litter tray setup, and scheduled veterinary check-ups to catch any deterioration early are all components of keeping the colon functioning as well as possible for as long as possible.