Does canned food cause diarrhea in cats?

A happy cat after having surgery to remove a piece of foam that was blocking his intestines

A very common thought among cat owners is that canned food causes diarrhea in cats. In fact, last Friday, one of our technicians had a conversation about that exact topic no less than three times!

1) Someone commented on a Facebook post with a question about her neighbor's cats. Her own cats thrive on a canned diet, but her neighbor objects, saying that it gives her cats diarrhea.

2) A woman brought in a kitten for a first visit that was having chronic soft stools and gas. She was concerned that the kitten was getting diarrhea from the canned food, but switching to a dry food did not significantly improve the problem.

3) At a dinner party, a friend leaned across the dinner table and said, "Not to be indelicate, but I'd like to pick your brain about my 3 year old cat's soft, smelly stools." His wife is concerned that canned food was the culprit, but the cat has been having diarrhea since they got her, and cutting out the canned food did not solve the problem. She has had her stool tested and she is up to date on vaccines. They had just moved to a new home and wondered how to approach a new veterinarian about the problem.

Most of the time, diarrhea in cats is not caused by eating canned food. Canned food is very close to what a cat would eat naturally, in the wild - the nutrient balance and moisture content of canned food is close to that of a mouse - and more natural than dry kibbles. It can be easy to blame diet for a cat's smelly, soft stools, but more often, we need to do some detective work to get to the root of the problem.

How do you diagnose the cause of diarrhea?

Usually, when presented with a cat that is having diarrhea, the veterinarian will recommend that the cat be checked for intestinal parasites. That is usually a very treatable reason to have chronic diarrhea. In Michigan, in Oakland County, in 2014, 1 in every 15 cats was positive for roundworms (compared to 1 in 46 dogs). It can also be a very difficult diagnosis to reach. When we test cats for intestinal parasites, the accuracy of the testing has a lot of contributing factors:

- the age of the stool sample. The older the sample, the less accurate the test. Usually a sample should be tested within 24 hours. Some parasites may be absent from the stool unless it is taken directly from the cat to the microscope! Tapeworms are mobile when they are deposited in the litterbox with your cat's stool, so they may wiggle off the stool before it is collected for testing. Tapeworms are more frequently diagnosed by observation of tapeworm segments on the hairs around the cat's anus than by bringing in a stool sample.

- the amount of stool. If a cat is having frequent, terrible diarrhea, it may be difficult to collect a sample, because only small amounts are produced very frequently.

- the life stage of the parasite. Some intestinal parasites do not shed eggs with every stool sample. When we look at a stool sample, we are most commonly looking for the eggs of the parasite, not the worm, itself. Other parasites are single-celled organisms and shed frequently, or their populations may wax and wane. Toxoplasmosis is an infection with a single-celled organism. Cats that are infected with this parasite will start shedding eggs (oocysts) in their stool  between 3-10 days after becoming infected and will only shed these oocysts for a total of 10-14 days. Ever. If you don't test a stool sample within that period, a stool sample will not diagnose this parasite. After that time frame, Toxoplasmosis infection must be diagnosed with blood titers that check for Toxoplasmosis antibodies.

For more information about cats and parasites, visit the Pets and Parasites website.

Sometimes, it may require that we test multiple stool samples before we are able to locate the parasite in the stool. One of our technicians had to check her cat three times before we were able to locate the Giardia that she was pretty sure was infecting her cat.

In cases where we suspect a difficult to diagnose parasite, or a viral or bacterial cause of diarrhea, we may recommend a "diarrhea panel". This test requires a larger stool sample and checks for two species of Campylobacter, Clostridium perfringens alpha toxin (CPA) gene, Cryptosporidium spp., feline coronavirus (FeCoV), feline panleukopenia virus, Giardia spp., Salmonella spp., Toxoplasma gondii, and Tritrichomonas foetus with PCR testing. A PCR test allows for certain types of DNA to be sorted out of a mixture of different types of DNA so that they can be identified. In this way, the laboratory can sort out the normal intestinal bacteria from bacteria that cause disease (are pathogenic), and find traces of parasites that may be present in small quantities, or identify viruses that may be present.

Hairballs can often be a culprit of intestinal maladies in cats. Sometimes, when the hair builds up in the system instead of passing normally, it can be a sign of a bigger issue - skin allergies or external parasites causing the cat to groom excessively, or decreased gut motility (the speed at which food moves through the digestive tract).

Another hairball - too large to pass through the stomach sphincter

Sometimes, a cat may have abnormal anatomy - here, the cat has a gastric diverticulum - a dead-end pouch off the stomach

This cat has a duodenal diverticulum - a dead-end pouch off the upper part of the small intestine

Sometimes, the intestinal problem is related to something the cat ate...anything from rubber bands, shoe strings and hair scrunchies to difficult to digest plant parts, to creepy, grinning toy parts...

Additional testing that might be recommended is highly dependent on the age of the cat, its unique symptoms, and the veterinarian's physical exam. It is highly likely that abdominal x-rays will be recommended. Special contrast studies may be recommended based on the results of the first films - for this, either barium or air will be introduced into the cat's intestinal tract for better imaging. Various blood tests may be recommended - from FeLV/FIV testing, to metabolic testing of kidneys, liver, glucose levels, thyroid levels, or pancreatic function testing.

 

What causes diarrhea in cats?

Sometimes, a cat may have a sensitive stomach that causes them to have diarrhea when their food is switched too rapidly. If they have eaten only dry food all their lives and are suddenly offered only canned food, in this case, canned food may cause diarrhea. However, if you transition food gradually, this should prevent diarrhea related to food transition. Cats may have a sensitivity to a certain protein in their diet. Very commonly, we hear of cats with beef sensitivities, though more in the context of vomiting versus diarrhea. (It make some sense, since we're pretty sure that domestic cats do not naturally hunt down cattle for dinner. Lions, yes. Fluffy, no.) It may be that a cat will have an intolerance to a particular brand of canned food, too, but rarely does canned food as a whole food group cause diarrhea. This would be similar to a human being unable to eat any type of soup or stew without digestive issues.


Besides intestinal parasites and food transitions, other problems that can cause diarrhea in cats include:
- viruses such as Distemper, Feline Leukemia, FIV, and Coronavirus/FIP
- toxin ingestion - plant or others
- Salmonella
- fungal infections
- body-system diseases including: kidney disease, hyperthyroid disease, pancreatitis, and diabetes
- cancer
- inflammatory diseases such as inflammatory bowel disease (IBD), fiber-responsive diarrhea, colitis
- pancreatic insufficiency
- foreign body ingestion (your cat ate a toy!) or other bowel obstruction (hairball, constipation)
- spoiled food
- certain medications (for example, some antibiotics are commonly known to cause diarrhea)

It may be yucky to look at, but using this chart to score your cat's stool can be very helpful!

What can I do to help the veterinarian diagnose my cat?

When trying to hunt down the cause of a complex diarrhea case, it may be helpful to keep a diary of what food you fed your cat each day and rate their stool consistency. We tend to sort cats' stools into the following categories:

- solid, normal stools - "Tootsie Rolls"
- soft stools with some form, but may appear to be "melting", also known as "soft serve stools"
- soft stools with little to no form - "pudding stools"
- liquid diarrhea, may be confused with urine in clumping litter, may be volatile, often the cat may be  unable to make it to the litterbox. This liquid may be brown in coloration or may be clear and difficult to distinguish from vomit.

Note any blood or mucus in the stool. Fresh red blood (frank blood) may be related to irritation of the intestinal tract or anus. Dark, tarry stools or blood that looks like coffee grounds contains older, clotted blood and is a more critical and severe concern than fresh blood. Mucous in the stool is often thick and clear and can be passed with the stool or separately. You may want to snap photos of the diarrhea to show your veterinarian. It can often be helpful, and we will never be offended. Note the frequency of the diarrhea and any other symptoms your cat may have.

When should you see the veterinarian?

Diarrhea is often considered to be a smelly nuisance, however, significant, chronic diarrhea can cause dehydration and malnutrition and can become a life threatening situation.

Contact your veterinarian right away if your cat’s diarrhea:

• is accompanied by repeated vomiting, lethargy, loss of appetite, abdominal pain, generalized weakness, or fever. Vomiting of a dark green liquid (bile) is commonly an indication of a complete intestinal blockage.
• contains large amounts of frank blood.
• is black or tarry in color.
• might be related to ingesting something toxic.
• occurs in a kitten under nine months of age, particularly if vaccines were missed.
• occurs in an elderly or medically frail animal.
• fails to respond or gets worse despite 48 hours of symptomatic home care.

Your cat wants to stop having diarrhea as much as you want him to!

 If you are new to an area and are not sure how to approach a new veterinarian with your problem, it may be best to simply collect a fresh stool sample and take it into the office. A stool sample can often be analyzed without first seeing a cat, though if medication needs to be dispensed, an exam will be necessary. This is because pharmacy laws in most states require an established doctor-patient relationship before any medication can legally be dispensed. If the parasite exam is negative, you will also need to bring your cat in for an exam and consultation about your cat's lifestyle and unique characteristics, so it may be best to contact the new veterinarian and schedule an appointment and bring a stool sample with you at the same time. Having your records sent from your old veterinary hospital to your new hospital will also be helpful, because it will give your new veterinarian an idea of your cat's past weight gains and losses, vaccine history, and any bloodwork or x-rays that have been done in the past.

Additional resources:
Pet Education: Diarrhea in cats: Causes, Diagnosis and Treatment
Cat Diarrhea Causes, Symptoms, Treatment and more