Diarrhea in Cats: When Loose Stool Signals Something More

Diarrhea in cats is one of those things that is usually minor and occasionally the first clue to something serious, and the trick is knowing which you are looking at. A single loose stool after a change of food is rarely worth worrying about. Diarrhea that goes on, or keeps coming back, is a symptom rather than a diagnosis, the visible end of any number of possible problems, and in an older cat it earns a closer look. It also does real harm on its own, by draining a cat of the water and salts she needs, which is what makes persistent diarrhea worth acting on rather than waiting out.

This covers when diarrhea is a problem, what tends to cause it in a senior cat, and what helps. What is behind your own cat's diarrhea is a question for your vet, since the causes range from the trivial to the serious and telling them apart takes an exam.

When is diarrhea a problem?

A brief bout often sorts itself out. Cornell notes that an abrupt change in diet, for example, may cause a cat to experience diarrhea for a few days, and that kind of short, one-off episode in a cat who is otherwise well is usually nothing to fear. The line to watch is duration and company. VCA gives a clear threshold: if frequent liquid or semi-liquid stools persist for more than two days, you should consult your veterinarian. Cornell adds the other half, advising a visit if the diarrhea persists for longer than a day or two and the cat is also showing systemic signs, such as poor appetite, lethargy, or vomiting. In a senior cat, persistent diarrhea is a reason to call.

How urgent is it?

Most diarrhea is mild, but the fluid it costs can add up fast in a small, older body. Use duration and how she is otherwise doing to gauge it.

• Worth noting. One or two loose stools, perhaps after a diet change, in a cat who is bright, eating, drinking, and herself. Keep her on her usual food and watch for a day.
• Book a visit. Diarrhea that lasts more than two days, or keeps returning over weeks, even if she seems otherwise well. Chronic or recurring diarrhea points to something that needs finding.
• Same day, or an emergency clinic. Diarrhea with obvious blood, or that comes alongside repeated vomiting, marked lethargy, a painful belly, or signs of dehydration such as tacky gums and skin that stays tented when gently lifted. The combination of diarrhea and vomiting is especially draining, because it loses fluid from both ends at once.

What causes diarrhea in a senior cat

The list is long, which is Cornell's own point: many feline health conditions may manifest themselves in diarrhea. VCA groups the usual suspects as infection with bacteria, viruses, coccidia, or parasites such as worms, non-infectious irritants such as chemical toxins or poisonous plants, and changes in diet or food intolerances, and adds that longer-running cases can come from food allergies, severe bacterial or viral infections (such as panleukopenia), inflammatory bowel disease, organ dysfunction, cancer, or other systemic illnesses. A few of these matter especially in an older cat:

• Inflammatory bowel disease. IBD is a common cause of chronic diarrhea in middle-aged and older cats, often alongside weight loss and vomiting, and it can be hard to tell from intestinal cancer without a biopsy.
• An overactive thyroid. Hyperthyroidism can loosen the stool along with its more familiar weight loss and big appetite.
• Parasites. Even indoor senior cats can carry them, and they are one of the more fixable causes once a stool sample finds them.

What the vet does, and what you can do

Because so many things cause it, a lasting case is worked up step by step: a history, a physical exam, and a stool sample first, then bloodwork and, if the diarrhea persists, imaging or a biopsy to separate inflammatory bowel disease from cancer. The most helpful thing you can bring is a clear account and, if you can manage it, a fresh stool sample.

At home, the priority is fluid, since Cornell explains that diarrhea causes insufficient absorption of nutrients, water, and chemicals called electrolytes, and VCA warns that severe or prolonged diarrhea can result in significant dehydration. Keep fresh water available and make sure she is drinking. Do not give human anti-diarrheal medicines, several of which are toxic to cats. A short spell on a bland, vet-recommended diet can settle a simple upset, and getting her back onto a good regular diet gently afterward helps. Stool consistency is also the one outcome probiotics have any real support for, which makes a short course one of the more reasonable things to ask your vet about here, and a poor substitute for finding the cause. Its opposite, constipation, is just as common in an older cat, and both lean on the same fixes of steady hydration and the right food. If the diarrhea is not clearing, or she is also refusing food, that is the point to stop managing it at home.

When to see the vet

Book a visit for diarrhea that lasts more than a couple of days or keeps coming back, sooner in an older cat or one with a known illness. Make it a same-day call for blood in the stool, diarrhea paired with repeated vomiting or real lethargy, or any sign she is becoming dehydrated. Diarrhea is common, and most of it passes, but the version that lingers is usually pointing at something your vet can treat.

Biscuit has a sensitive stomach that a new food can upset for a day, and I have stopped panicking over the occasional soft stool that clears by morning. What I no longer ignore is the kind that stays, or arrives with a flat, off day, because the sort of diarrhea in an old cat that keeps going is almost always trying to tell me something.

Frequently asked questions

Why does my senior cat have diarrhea? The causes span a wide range, which is Cornell's own point: many feline health conditions may manifest themselves in diarrhea. A one-off loose stool is often just a diet change or a mild upset. When it lasts or keeps returning in an older cat, the causes worth knowing are inflammatory bowel disease, hyperthyroidism, parasites, and, less often, intestinal cancer. Your vet sorts out which with an exam and a stool sample.

How long is too long for a cat to have diarrhea? About two days. VCA advises that if frequent liquid or semi-liquid stools persist for more than two days, you should consult your veterinarian, and Cornell that a visit is due if the diarrhea persists for longer than a day or two and the cat is also showing systemic signs, such as poor appetite, lethargy, or vomiting. In a senior cat, do not let it run on.

Can stress give a senior cat diarrhea? Yes, briefly. Cornell counts a stressful situation, such as a long car trip or a stay at the clinic, among the things that may produce a brief episode of loose bowels, and an old cat who dislikes change is a good candidate. The test is the same as for a diet change: it should settle within a couple of days once the stress has passed. Loose stool that outlasts the trip or the visitor is no longer stress and needs the usual look.

When should I worry about my cat's loose stool? Worry when it comes with other signs or will not clear. Treat it as same-day if you see blood in the stool, diarrhea alongside repeated vomiting or marked lethargy, a painful belly, or signs of dehydration such as tacky gums. The pairing of diarrhea and vomiting is especially draining, because a small, older body loses fluid from both ends at once.

Sources

• Cornell Feline Health Center, Diarrhea
• VCA Animal Hospitals, Diarrhea in Cats