Pet Articles

Cat Diarrhea – Constipation – Intestinal Disorders

Intestinal disorders

  • Diarrhea may be trivial or life-threatening
  • Bowel problems can originate outside the bowels
  • The liver and pancreas are vital for digestion

The intestines are a vital part of the immune system, and some inflammatory bowel diseases and dietary allergies are really manifestations of immune disorders.


Damage to the digestive system may result in diarrhea. It may be painful, be accompanied by vomiting, or contain blood or mucus. It can be associated with an increase or loss of appetite, normal behavior, or severe lethargy. From its characteristics, one can reasonably accurately determine the causes of diarrhea, which include:

  • Eating grass
  • Dietary allergy or sensitivity;
  • Food poisoning;
  • Parasites (such as Giardia);
  • Viruses (FPV, FeLV, FIV, FCoV);
  • Bacteria (such as Campylobacter);
  • Drugs;
  • Hyperthyroidism.

Treatment: Diarrhea is treated symptomatically. The known cause is eliminated. Withhold food for a few hours, but allow your cat to drink. Fluid therapy is essential when acute diarrhea is caused by FIE (feline infectious enteritis) infection (see p.214).

Many experts recommend feeding a cat its regular diet to provide the gut flora with familiar food. Antibiotics are never used unless bacterial infection is suspected.

Consult your vet at once if your cat is lethargic, has a fever, or passes blood.

Ask the vet

Q: Does milk cause diarrhea?
A: Any dietary change may cause diarrhea.
Milk may cause it in cats that no longer produce sufficient amounts of the enzyme lactase, as they did as kittens. If your cat suffers from diarrhea when it drinks milk, feed it lactose-free milk for cats, available in supermarkets.

If your cat is badly dehydrated by persistent diarrhea or vomiting, it may need to be put temporarily on an intravenous drip.

Inflammatory bowel disease (IBD)

This is a group of increasingly diagnosed diseases related to the immune system. Affected cats, often middle-aged, usually have chronic vomiting and diarrhea, defecate more frequently, lose weight and litter training, and look malnourished. Treatment: Your vet will start your cat on a hypoallergenic diet and prescribe immune-suppressing drugs, such as corticosteroids.
Cats with IBD respond to dietary supplements. Antioxidants, such as zinc, selenium, and vitamins A and E, may improve the immune system. Bioflavonoids, such as proanthocyanidin, may work with vitamin C to support immune function and scavenge free radicals. N-acetyl glucosamine may reduce inflammation. Vitamins B12 and K and folate are also beneficial.

Intestinal obstruction

The most common cause of this is a tumor invading the gastrointestinal system. Affected cats may vomit, have diarrhea, and lose weight. By then, your vet will probably be able to feel a lump in the abdomen. Surgically removing the mass and associated tissue is successful if it has not spread elsewhere.


Although not uncommon, constipation can be serious if the colon dilates into a megacolon and loses its function. In most cases the reason for megacolon is unknown, but it can be caused by diet, trauma, and neuromuscular disease. Affected cats vomit, appear depressed, stop eating, and strain to pass stools.

Constipation is reasonably common in older cats and may have any of several causes. This X-ray clearly shows unexpelled feces in the colon.

Identifying intestinal problems through stool analysis

Characteristic Cause

  • Watery
  • Covered in jelly (mucus)
  • Oily, greasy
  • Bubbly
  • Rapid transit through gut
  • Large-intestine condition (colitis)
  • Malabsorption condition (fat)
  • Gas-forming bacteria in intestines

  • Tarry, black
  • Clots or bright red
  • Pasty, light
  • Yellow-green
  • Bleeding from upper digestive tract
  • Bleeding from lower digestive tract or anus
  • Lack of bile from liver
  • Rapid transit through gut
Frequency and quantity:
Small amounts very frequently Large amounts 3-4 times daily
Irritation to colon
Digestion/malabsorption condition in small intestine

  • Normal
  • Unpleasant
  • Rapid transit/malabsorption
  • Bacterial action (fermentation), blood
Other signs:

  • Vomiting
  • Weight loss
  • No weight loss, good appetite
  • Gastroenteritis
  • Malabsorption, increased metabolism
  • Large-intestine condition

Treatment for constipation

  • Mild cases are treated with enemas given by the vet. Do not do this at home. Given incorrectly, an enema can cause severe damage.
  • Soak dry food in equal parts of water and feed only when it is fully absorbed. This increases fluid consumption.
  • In multicat households make sure each cat has its own litter box and clean it regularly.
  • A little cow’s milk, bran fiber, or psyllium (ask your pharmacist) added to a cat’s diet may act as a laxative or increase the frequency of defecation.
  • Use a mild laxative, such as lactulose, as instructed by your veterinarian.
  • In the most serious instances, surgical removal of the colon is an option. Cat owners say their cat’s personality and elimination habits return to normal.

Anal-sac irritation

Anal-sac blockage or infection causes a cat to groom its bottom obsessively, so much so that it licks the hair off its hind legs and belly. Irritation from tapeworms causes similar, but less intense, licking. Infection causes a swelling on the affected side, to the left or right of the anus.

Treatment: Uncomplicated blocked anal sacs are emptied by squeezing by your vet. If the sac swells and bursts through the skin, producing a draining abscess, your veterinarian will prescribe antibiotics.

Distended belly

Obesity is the most common cause of a distended abdomen. Other reasons are: tumors; accumulation of fluid (ascites), which develops most frequently as a result of feline infectious peritonitis (see right) or liver disease; and a general enlargement of organs as a result of, for example, womb infection (pyometra), immune disorders (enlarged spleen), or an overactive adrenal gland (enlarged liver). See your vet if your cat’s abdomen is distended and you do not know why.

Feline coronavirus (FCoV) and feline infectious peritonitis (FIP)

Some strains of FCoV cause mild diarrhea. Others cause a serious, often fatal infection called feline infectious peritonitis (FIP). Shared litter boxes an( mutual grooming are the ways these viruses spread in multicat households. FIP occurs in two different forms: dry, usually affecting the lungs, and wet, leading to fluid accumulation in the abdomen (ascites).
Prevention and treatment: One or two cats living in a home are at little risk. If more cats are introduced, however, they should be blood-tested for FCoV. Limit fecal contamination by cleaning the litter box daily and keeping the cats’ food away from their litter box(es). The nasal vaccine is not recommended for routine use but could, in theory, be useful for vaccinating FCoV-negative cats before they enter FCoV-positive environments. Immune-suppressing drugs, such as corticosteroids, are at the heart of treatment. Unfortunately, once ascites develops, any form of treatment is unlikely to be successful.


A loss of appetite (anorexia) can be caused by a range of problems inside o outside the digestive tract. They include pain, injury, disease, fear, stress, an unpalatable diet, and loss of the sense of smell. You should always contact your vet if your cat stops eating.

Liver and pancreatic disorders

Small-bowel disease can ascend into the bile duct, which goes to the liver, and is also connected to the pancreas. Uniquely in cats, small-bowel disorders can lead to pancreas and liver disease. Also, many conditions cause hepatic lipidosis, the most common liver disorder in cats.

Hepatic lipidosis (HL): HL occurs twice as often in females, especially fat females, as in males. It can be triggered by poor nutrition, obesity, other diseases, or simply not eating. Fat cells accumulate in the liver and affected cats lose their appetite, lose weight, and refuse to eat.
Treatment: HL is life-threatening. Cats must eat, and the most effective way to ensure good hydration and nourishment is by surgically installing a stomach tube (gastrostomy) that remains in place for about a month.

Liver shunt: After damage from chronic liver disease, blood vessels from the intestines may bypass the liver. Blood does not get purified of substances from the intestines, such as ammonia. These circulating substances cause brain inflammation. Affected cats dribble and stagger, act lethargic, experience seizures, or twitch.
Treatment: This condition can be treated by diet management or surgery.

Drug-induced liver disease:

Some drugs, safe to humans and dogs, are toxic to cats, causing hepatitis. They include:

  • Aspirin;
  • Diazepam (Valium);
  • Iron supplements;
  • Glipizide (for diabetics);
  • Ketoconazole (for ringworm);
  • Methimazole (for hyperthyroidism).

Obesity in cats, especially females, can lead to the
common life-threatening condition hepatic lipidosis.

Pancreas problems

Chronic (ongoing) inflammation is the most common pancreatic disease in cats. Affected cats have nonspecific signs, like vomiting, diarrhea, lethargy, and weight loss. Diagnostic blood tests are not reliable in cats. A biopsy is needed for an accurate diagnosis. Chronic pancreatitis usually accompanies other liver and bowel diseases.

Cats rarely suffer acute (sudden) inflammation to the pancreas or exocrine pancreatic insufficiency, the most common pancreas disorders in dogs.

Diabetes mellitus: Insulin, produced in the pancreas, helps body cells absorb glucose. A lack of insulin causes blood sugar to increase and leads to diabetes mellitus (sugar diabetes), which affects about one in 200-400 cats. High blood sugar alone is not diagnostic for diabetes. Even mild stress increases a cat’s blood-sugar value. Diabetes typically causes increased drinking and urinating, combined with weight loss. The onset is slow and often missed by cat owners.
Treatment: Diabetes is often treated with insulin injections and a high protein, reduced-fat diet. Oral drugs to reduce blood sugar can be effective. Once diabetes-induced cataracts develop, their progress is irreversible.

Excerpted with permission from Cat Owner’s Manual by Dr. Bruce Fogle published by Dorling Kindersley Copyright 2003. All rights reserved. You can purchase the Cat Owner’s Manual at

30 Responses to this Article, So Far

  1. Avatar joan brooks says:

    took a cat to vet for dental, brought him home that day as antibiotics had to kick in before the surgery. 3 cats got sick. I am assuming from his visit to vet. One is 13 and diabetic,one is 7 and overweight. The dental patient is better. took all 3 back to vet for 3 days stay. Vet says they may have contacted intestional virus while there. The diabetic one has not eaten for 2 days and the 7 yr old one has not done anything except lay around and cry and throw up fluid. He had a 103 temp when i took him to vet. He is still warm to the touch and the inner eye lid is showing. I am taking them both back tomorrow(hopefully they will survive the nite) any suggestions or ideas? It is a cat specialty clinic. I dont think either one should have been sent home till they were eating and temp dropped

  2. Avatar Kc says:

    My 1yr old kitten has been having persistent diarrhea. We recently got a dog, and the kitten has been sneaking the dog food whenever he can get away with it. I have since put the dog food in a location he has not been able to get it, and also put him on an all water diet for 24 hours, and then I gave him some boiled chicken with white rice.
    I just got puppy fixed, so our vet savings is down at the moment so we cannot take him there just yet, I am just wondering if there is anything else I can do, until I can take him to the vet in 2 weeks.

    • Avatar Marko says:

      Yes – at least call your vet so he/she can tell you how serious this is. Persistent diarrhea is serious and a water diet is NOT A GOOD CURE.
      2 weeks is WAY too long to wait. This poor animal needs a doctor now!

  3. Avatar Val says:

    One of our outdoor cats has been pooping constantly. He’s lost a lot of weight and now has what seems to be a “growth” of something on his rectum. So far, none of his siblings have come down with it. I’m sure this is something serious and life-threatening, but we can’t afford a vet at all. Is there anything I can do or give him to ease his suffering for now?

    • Avatar Marko says:

      I hate to say it but we are pet lovers on this site and so most of us will beg/borrow/steal to help a suffering pet.

      i would call my vet to see if they will l take payments over time….or maybe a vet medical school can offer cheaper prices.

      Guessing that this is life threatening is the WRONG move here and will definitely harm your cat. it really might not be that serious….but only a doctor will know.
      Good luck!

  4. Avatar KAC says:

    My cat has been dropping little bits of poop. He is litter trained, but very seldom uses the litter box. He usually meows to go outside to use the bathroom. What can be wrong with my cat? What do I need to try?

    • Avatar Marko says:

      maybe the cat is constipated? A vet visit is in order here and during that visit you should mention your cat’s diet.
      Good luck.

  5. Avatar Renesmia says:

    My 3 month old kitten has had the runs for 3 weeks now. He has been to the vet two times. The first time they gave him a de-wormer and the second time they “tried” broad spectrum antibiotics. This is all to no avail. The poor cat is miserable, and his back side is all swollen.The skin on yhis hind legs are getting red and irritated. He is getting a bath more than one a day to try and keep his skin clean. Are there any over the counter remedies that my cat can try to calm his digestive tract? He still eats, drinks, play and purrs but I am really worried. There has to be something that I can do to help him.

    • Avatar Marko says:

      Sorry to say this but this is still a medical problem. The cat needs to be seen and tested by another vet if you aren’t happy w/the one you are using.
      Good luck.

  6. Avatar Tracy says:

    I need help. I adopted an DLH male from my local shelter about 2 years ago. He is a wonderful little guy but I have one problem. He has had persistent diarrhea pretty much since I brought him home. Occassionally he will relieve himself in other areas of the house instead of in the litter box. Could this be a medical problem, or could it be stress related since he came from a shelter where he was abused to a house with 5 other cats?

  7. Avatar Kira says:

    I foster kittens for my local animal shelter. I have recently noticed diarrhea with dark traces of blood. I am currently fostering four, and I cannot isolate which one is having problems. However, all seem healthy, active and eating well. If the bloody diarrhea persists, what should I do?

    • Avatar Marko says:

      You should get the shelter’s VET involved….immediately.
      Bloody diarrhea in humans or pets is not a condition that should be diagnosed and treated on the Internet.
      Good luck!

  8. Avatar Sandra says:

    Have a logistical problem here- I live in a small town in South American with my 12 year old Siamese. She is straining to poop, is it better to give her an eniema or take her to a vet by taxi- about 40 minutes?
    Thank you- Sandra in Chile

    • Avatar Marko says:

      100% a vet visit is required – especially if this has been going on for more than 24 hours.
      Good luck

    • Avatar Genie says:

      My kitten has the exact same problem as Renesmia kitten. She sometimes poops in her litter box and other times she wont. My mom told me she’s poopin like that cuz I changed her food. I had her on cheap cat food. Now I have her on good kitten food. Kittens are suppose to have kitten food not cat food. Trust me there is a difference in the two. I also read online that 2% milk helps.

  9. Avatar aamn says:

    Please help urgent , my cat has stop eating feed from past 3 days and all of sudden after 3 days started eating and after eating vomits out eaten food and goes for stick blackish greenish smelling toilet and does not move and sits on on same place mood-less, what to do please suggest and safe my pet cat urgent .

    • Avatar Marko says:

      This site is a pet lovers site and when our pets are suffering ….we take our pets to the vet.
      Your pet is suffering, please take it to see a vet and borrow the cash if you have to.
      Good luck.

  10. Avatar Jaime says:

    I have a 6month old female kitten who has had a couple urine accidents (outside the litter box, in bathtub), I got home from work and she had diahrea with blood and mucus in it in our bath tub. She is purring constantly and very affectionate/playful as usual. I will call the vet in the am for an appointment for her. Just wondering if anyone has had this before. I have had cats all my 34yrs in life and never encountered this. Possibly worms or parasite? I do have two other cats that are fine.

    • Avatar Marko says:

      Really hard to say what’s causing this without an exam. There are several things that can cause bloody diarrhea – but there is zero good reason to speculate on possible causes…..and this 100% requires a vet appointment.
      and I’m glad you are seeing a vet ASAP for this as this is not normal of course.
      The fact that the kitten is purring is NOT a sign of anything, meaning the purring does NOT mean that the cat “is not that sick”.
      Only a vet can determine this and this pet NEEDS an appointment for sure.
      Good luck!

  11. Avatar Diana says:

    My elderly 23 year old male cat takes Lactalose 2 ml 2- 3 times a day and Cisapride.5 ml 2 times a day. He takes meds for blood pressure and hyperthyroid and tramadol for arthritis pain and potassium.

    He has already had 3 enemas at the vet. The last was only a week ago. He is not pooping.
    Any suggestions? He needs more of something for his constipation. Right now, he is still eating. Pretty soon, as the poop builds, he will start vomiting and stop eating. What can I do?

  12. Avatar Laura says:

    My cat was prescribed Methimazole for thyroid problems. The vet never told me it could cause constipation or a severe blockage. Shouldn’t they have told me this? She has been on it for about 4 weeks and had bloody urine (also a side effect, so we stopped the medication) and now constipation that results in small watery drops of blood. I fear we will be making a very hard decision in the next few days, as my kitty is 17 years old and we won’t put her through extensive surgery for this. Am very angry at the vet.

  13. Avatar makayla says:

    My kitten ( not sure how old but guessing 8 weeks) has a real bloated hard stomach and did have diarrhea, her tummy is really hard and her poop stinks bad. I’m having my mom call the vet in the morning to set up an appointment and to see if we can pay in payments but is there anything anyone can suggest??? Please help

  14. Avatar Vivien Sorey says:

    My cat has IBD and is on meds. But today I noticed that her back legs appear wet. I bathed her.but within a few hours they looked wet again. What can this be?

  15. Avatar Mina says:

    My 8.5 year old cat appears to have constipation for the first time in his life. He is a very big cat and obese (20 lbs). he has always been big. I got a new dog this past week and one day after having the dog at home my cat had a very malodorous loose stool. he then did not have a bm for 2 days (normally goes 2-3x/day) and last night finally had a bm with lots of straining (hard, small). THen this morning it was loose stool again (not diarrhea, but very maladourous and small amount). He is eating normally, no temperature, everything else seems fine. He is being kept in my bedroom as he is afraid of the new dog. Could this be due to stress? I would like to add that my cat has not gone to the vet in over 4 years as he is very difficult (last vet called him an “asshole”). He has not been able to have a checkup since he was a kitten as no vet seems to be able to examine him. I have been lucky he has never been sick.

    • Avatar Mina says:

      also wanted to add that he and my dog have not had any actual physical contact. just me holding him up in the same room as my new dog or putting him down on the couch in the room when the dog is in the crate. these interactions have only lasted for a minute or two as i can tell he is stressed so I take him back to the bedroom

  16. Avatar TIna says:

    My 15 year old cat has suddenly gotten urine tract infection. Brought her to the vet, she was checked and she doesn’t have stones or crystals. and they gave her antibiotics. The antibiotics just relieved her pain and made her pee again, which was good. But then it got her very very constipated. Anyway when the antibiotics finished, the infection came back. Now I’m doing a culture and waiting. In the meantime my cat is constipated badly. I gave her laxatone and lactulose and olive oil… almost the 3rd day and not worked.. The vet said that keep doing everything or I have to bring her in and they have to remove. Help me I want to get rid of this constipation, Do you think she can give me something else instead?

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