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Featuring Demian Dressler, DVM and Sue Ettinger, DVM, Dip. ACVIM (Oncology), authors of The Dog Cancer Survival Guide

Signs of Dog Cancer and Decompensation

Updated: November 22nd, 2018

People are often stunned to find out their dog has cancer. Why? Because cancer seems to hit out of the blue. I often hear “but he’s been fine until the last couple days!” In this article, I’m going to take just a minute to explain why “cancer” seems to happen overnight. (Hint: it’s because of dog cancer decompensation … not cancer itself.)

“Signs of Dog Cancer” Are Really “Signs of Dog Cancer Decompensation”

Search for the warning signs of dog cancer, and you’ll find plenty of listicles that include items like the following:

  • a new lump that is hard
  • a limp
  • coughing
  • weight loss
  • loss of appetite
  • vomiting
  • diarrhea
  • thirst changes
  • bad breath
  • yellowing of the skin or eyes
  • abdominal swell
  • difficulty breathing
  • spontaneous bleeding
  • unusual odors

But those are not signs of cancer. They are signs of dog cancer decompensation.

Your dog has had cancer for a lot longer than you realize. The signs listed above are actually signs that your dog’s body has stopped being able to compensate for cancer, and her body’s normal functions are breaking down.

Looking back at your dog’s last few months, or even year, you might think I’m crazy.

How is it possible that a dog can act totally happy, eat, drink, move around, socialize … and have cancer?

Don’t sick dogs act sick? Well, let’s take a look at that.

Decompensation Defined

The clearest definition of decompensation I’ve found is this:

“Decompensation is the functional deterioration of a previously working structure or system.”

Every organ and system in the body function well under normal circumstances. And every organ is designed to have lots of built-in safety systems so that if something goes wrong, the organ can STILL function while it repairs itself.

So, when a medical problem is introduced, the body can “compensate” for it. Let’s take a non-cancer example.

Say you are using a hammer and hit your thumb. That’s our medical problem: your bruised thumb.

The tissues immediately swell up. That’s the immune system sending fluid to the area both to keep it from moving too much (which could further injure it), and also to bring white blood cells to the area to start helping repair the damage.

Your immune system is “compensating” for the medical problem by sending help.

Now, normally, your thumb would heal in a few days or a week. You might not even really notice the thumb’s hurt, after a while.

But let’s say that you damaged your nail very badly in the strike. The body simply can’t repair the damage done. After a week or so, you might find your nail falling off. Now it takes months for your nail to grow back in.

Well, that’s your “decompensation,” right there. Normally, you have a nail on your thumb. But now, you don’t. Your body could not compensate for all the damage done.

So now you’ve got a clear sign … for months … that you have been damaged, and that things aren’t normal.

When Safety Systems Fail

When your dog has cancer, her body will kick in all sorts of safety mechanisms (depending upon where the tumor is) to keep the body working properly. Dogs act normally during this time.

So do people, if you think about it. You probably know someone who has had cancer. Did they feel terrible right at the beginning? No … we don’t start really noticing symptoms until cancer has disrupted our health. Until our safety systems start failing.

So what we see listed as the “signs of cancer” are not really signs of cancer at all. They are signs that cancer has gone past a certain tipping point.

They are signs of dog cancer decompensation.

They are signs that cancer is in a late stage.

In other words, once a dog starts to act sick, it’s already late in the game.

What to Do If Your Dog is in Decompensation

If your chest is tightening as you realize that your dog isn’t “suddenly sick,” but may have had cancer for a while, please take a few deep breaths.

This is a difficult concept to accept, and it’s totally normal to feel, well, to feel awful about it. Just because we usually find cancer late (after decompensation) doesn’t mean that we can’t do anything about it. There are lots of things to do to help your dog’s life quality and even optimize longevity.

So if you haven’t had a diagnosis yet, get one. Knowing what you’re dealing with will help you to make decisions. And if you do know it’s cancer, don’t be afraid to get a second opinion, just to make sure. Any professional vet will be okay with this, and it wise to double check to make sure the dog cancer journey is a path you are on.

Get the Dog Cancer Survival Guide to read more on End of Life and Hospice Care, in Chapter 25

Bottom Line: Test Healthy Dogs for Cancer

The fact is that one out of two dogs over ten gets cancer, and one out of three overall get cancer. It’s the number one killer of dogs at this point. So we should all be taking it very seriously, and testing dogs for cancer, earlier, when they seem healthy.

Starting in the last quarter of life at the earliest, get annual (or more frequent) imaging done to look at internal organs: X-rays, ultrasounds, etc. Don’t ignore lumps and bumps, but get fine needle aspirates, biopsies. Blood and urine tests can serve as critical screening tools.

When’s the last quarter of life? There’s a comprehensive list in my book for breeds and their average life expectancy, but you can also base it on weight:

  • Dogs up to 12 pounds live approximately 14 years, so start annual testing no later than 10.5 years.
  • Dogs 12-30 pounds live approximately 13 years, so start annual testing no later than 9.75 years.
  • Dogs 31-50 pounds live approximately 12 years, so start annual testing no later than 9 years.
  • Dogs 51-80 pounds live approximately 11 years, so start annual testing no later than 8.25 years.
  • Dogs over 80 pounds live approximately 9 years, so start annual testing no later than 6.75 years.

The reality is that when caught early, cancer is easier to treat and we have better chances of preserving life quality (and even extending longevity).

Best to all,

Dr D


Leave a Comment

  1. Joan Bollaert on August 17, 2021 at 2:39 pm

    Two weeks ago.. my 9yr old dog was eating, drinking and peeing more. Did labs and not diabetic. Only some blood in urine. He’s also lost 5lbs. Antibiotic given. The day after that started antibiotic he stopped eating and drinking water. I stopped the antibiotic after 3 1/2 days and he still hasn’t had any food or water in two weeks. Only had injections of fluid into body and ultra sound. Ultrasound didn’t detect anything significant but some suspicious areas and chest x ray was suggested. And in that xray it showed a large mass in his chest cavity. He is also in need of dental surgery but his teeth don’t hurt . I was thinking that perhaps his teeth hurt to eat, but that wouldn’t explain the not drinking of water. With the diagnosis of chest cavity mass, I made the decision to not proceed with that and wondered if putting him down the right thing to do and the best option for him at this point? He has lost 10lbs in two weeks and continues to not be interested in water or food. He cannot live without eating or drinking anything. Thank you. I have him scheduled for tomorrow but I guess I just need someone to tell me it’s ok. :(. Thank you. This is very difficult .

  2. Gina Douglas on June 24, 2021 at 2:07 pm

    I apologize I didn’t realize it was a blog I’m such a total mess but if anybody has any information that they can help me with with my Maddox please let me know thank you very much

    • Molly Jacobson on June 25, 2021 at 12:30 pm

      Hi Gina,

      Thank you for your post, and I’m sorry you’re going through this with Maddox 🙁

      It’s difficult to advise you online, of course. I agree that it seems like things are quite advanced. I would ask the oncologist the following questions:

      What do you think we will get from this chemotherapy in terms of life quality? How much extra time will I get? What kind of post-treatment care will this require? How often do I need to bring Maddox back? What are the signs you will be looking for to see if it is helping or not?

      Asking very specific questions like this will tell you more about what the vets think will actually happen. Will the tumors shrink? Will they go away? Or are we just buying time?

      Will the chemo address the fluid build up?

      I just watched a (human) loved one go through liver failure. I can tell you that when she had 14 pounds of fluid in her abdomen, she was in TONS of pain. She hurt EVERYWHERE and could not get comfortable until after they “tapped” her and drained that fluid out. I don’t doubt that a dog with fluid in the abdomen is in pain, too.

      So I would ask them about that. You need to know WHAT they are doing these things for, and what they think will be gained.

      Not because there is one right way — but because the answers will tell you whether the treatment is “worth it.”

      Finally, this article will help you to assess just how close you are to the end, when it’s time for you to think about it, you may be more prepared:

      Warm wishes,

  3. Gina Douglas on June 24, 2021 at 2:04 pm

    Hello Dr. Dressler
    My beloved Maddox just turned 7 yrs. old April, one mouth ago I had a feeling something was wrong because he was not interested in his food, however, he’s always been picky about eating I still felt something was wrong. I took him to the vet the very next day, they said he’s fine so I took him to another vet the next day, that vet did blood work an ultrasound and sent us to the hospital ASAP. We were there for nine hours while they were running test on him and had to come back the next day they aspirated 2.7 L of green liquid out of him and did a biopsy and told me that he had carcinomatosis but they never told me what particular type of cancer it was that it had spread to every organ throughout his body now a month later I had brought him back in and they drained another 2.3 L of fluid out of him and put Maddox on prednisone as well as cerenia. They want me to bring him back in on July 1st to talk about chemotherapy I’m skeptical about it because my thought is if the cancer has spread through every organ of his body and His intestines are all twisted up and they’re draining that much fluid off within a month I don’t know what quality of life he will have… I do not want him to suffer, I love them too much to put him through that just to be selfish and keep him here with me for another month or two just because I can’t let him go. I would just like to know your opinion on this please? Sincerely, G Douglas

  4. Elisha on November 20, 2019 at 2:10 am

    This explained it so well! Thank you for your insight!

  5. gino labiak on November 16, 2019 at 5:57 pm

    MY Aussie is 7 1/2 yars old healthy until last week had a limp one leg. Then it was another leg days later.. Blood work and X rays are fine but he has a hard time moving after he lies down. It has been one week. H e has a fever sometimes but we are giving tylenol per vet. He take steroid once a day into sixth day and antibiotic shot for a week. He hates to lie down knowing it will be hard to get up. He can go on a regular walk fine. Now he is lying still yelping when he moves his head. Every night seems like he can move less. Any clue before we get a specialist?

    • Dog Cancer Vet Team on November 18, 2019 at 9:05 am

      Hello Gino,

      Thanks for writing. As we’re not veterinarians here in customer support, we can’t offer you medical advice. You may find this article helpful, as Dr. D goes into detail on signals of pain, limping, and addressing pain, that you may find helpful. But your specialist will be able to run tests to find out what is happening and help you address them 🙂

  6. Patricia Ryan on October 17, 2019 at 5:58 am

    THIS IS ABOUT MY FRIENDS DOG WHO IS JUST COMING A YEAR OLD He is a lovely little dog he looks like he should go on a diet. At the start, he would eat and eat We took him to the Vet because he was finding it hard to brething The Vet said it could be his glands This has been going on for weeks Now today The Vet said it could be cancer He is just under a year old. In the last few days, he has gone off his food This is not like him HE WAS SICK IN THE CAR AS WELL The vet said it was in all his glans I do worry not just because I love the wee dog but My friend is so upset about it.

    MY friend ask me if the next lot of tests come back That it is all over would she have to have him put down I told her The Vet would say what would be the best thing to do

  7. Lisa Campbell on July 14, 2019 at 7:58 pm

    After 3 surgeries , Ive never felt so broken . So angry at the world . Angry at our over scheduled vet . Angry at the what ifs and no answer for the whys . I will tell you this book did help me pull myself back together . It just seems like there should be something else to save my only child. My precious girl . Id of spent whatever it took , drove miles and here I sit with you in my arms telling you ‘its gonna be alright when clearly its not ” .

  8. Joseph Tuttolomondo on April 9, 2019 at 4:34 am

    My Wife and I recently had to put our 10yr 3month old Golden “Winston” down this past Saturday. We went to the vet approximately two weeks ago due to Winston, out of nowhere, dry heaving, not constant, but a few times throughout the day. The vet said he was in great condition, didn’t hear anything in the chest, structure felt good, vitals were good, tested for heart worm, that was good. Then fast forward to this Saturday we wake up to Winston not being able to completely stand, his right front paw was noticeable knuckling. He was able to go outside and urinate, then about a 1/2 hour later I fed him, and then we walked him, he was still knuckling every so often but managed to pee and poop no problem, he even began to trot a little. At this point I’m thinking disc, arthritic issue so I left to my office for a few hours and when I returned home Winston was flat out on the ground and couldn’t get himself up. I managed to help him up but he still couldn’t stand completely on the wood floor so I took him on the patio which he was able to stand somewhat and managed to go into the grass to pee although then he just fell over. We immediately took him to a vet that was open and very reputable only about a mile away. They proceeded to take vitals which were great, chem15 which was normal, and she even listened to his chest and didn’t really hear much. Then the chest X-ray comes out which looks like a snowstorm and I knew the prognosis was not good. I take it from this article this scenario is more common than I thought. The last thing I wanted to do is euthanize my pup, he was an awesome Golden and its going to take me quite some time to accept this, its so painful! The day prior we did our usual evening walk by the lakes, rolling in the grass, playing with his brother Luke, showing no signs of any disease, crazy how this happens. We took great care of Winston, always the best for him, I even stopped all heart guard and flee/tick meds at the age of two and placed him on holistic products which prevented all those issues. The only thing that bothers me is putting him down, he looked healthy, eyes were clear, vitals were good, labs good, my wife didn’t want to see him suffer any more than he did the day of, he seemed to be declining in the office, and when I asked the vet for some type of time left with him, there was really no answer, hours, days, maybe. So painful. I lost my best bud Winston. Hopefully you can shed some light regarding making the right decision. Thank You.

    • Molly Jacobson on April 9, 2019 at 6:23 am

      Hi Joseph. No one will ever be able to tell you what would have happened if you hadn’t let him go, but every vet I know thinks one day too early is better than one day too late. Dogs are amazingly stoic, and we have to multiply the pain they seem to be in by ten, twenty, a hundred to get close to how strong it could be. It definitely sounds to me like you did the right thing. Lung cancer is very painful. I have family and friends who have described it as hell. That your boy lasted for so long with no complaints or symptoms proves how strong and wonderful and miraculous dogs can be. You are in shock right now and it’s natural to go over everything and wonder what if. But those questions are more part of the grieving process, I suspect, than indications that you did anything other than what was best for your boy. Warm hugs to you.

      • Joseph on April 9, 2019 at 9:56 am

        Thank you Molly for the reassurance and kind words. It’s just so difficult to accept.

        • Molly Jacobson on April 9, 2019 at 1:02 pm

          No doubt. It’s ok if it takes time to accept. Grieving has no rules.

      • Ana on April 13, 2019 at 9:00 am

        My husband and I lost our little dog Chewie a few days ago to cancer. He was 6 and 5 months. The only indication we feel we ever had was a dry cough that was few and far between. He was so bright and and alert and ate well and went to the toilet fine. He had monthly visits to the vet his whole life for his cruciate ligament operation follow up he had as a little puppy. He would have his heart listened to and we would briefly talk about his health which was always fine. At annual check ups he was fine too. When he was about 4 we had one bad incident where he lost his appetite for a day and vomited blood at night. We immediately took him to the emergency vet and they fixed him – he got better. They said it was some bacterial infection. Three weeks ago Chewie grew a golf sized ball on his hind leg. The moment we saw the lump in the morning we took him to the vet and they conducted biopsy on the lump. The vet was still unsure of the cause of the lump and we had a blood test two days later. Chewie was still fine except body out alignment to compensate for the lump. He was given Vitamin K and Niralone and sent home. We took him back to the vet for tests and observation almost every day that week. Just over a week later his panting got laboured and he had a dry cough when drinking water – worse than before. We thought it was a reaction to the medication. A week later he had a follow up check up. I insisted they do a thorough test including ultrasound and X-ray, only due to someone at work having just lost their dog to the dog having fluid around their heart and this being captured by such tests. The vet called me soon after with the result of the scan. This is a day my husband and I will never forget. Chewie was diagnosed with lung cancer, the scan showing metastatic lesions in his lungs and an enlarged liver at this point. We returned to the vet and noticed his breathing was so terrible he required oxygen. His quality of life was diminishing rapidly and we had no choice except to give him all our love in his last moments with us. It’s devastating and hard now days later to not have our little Chewie with us.

        • Ana on April 13, 2019 at 9:10 am

          Chewie was a Maltese x Shitzhu.

        • Molly Jacobson on April 13, 2019 at 4:23 pm

          I’m so sorry for your loss. It’s astounding how stoic dogs are, isn’t it? Chewie sounds like a wonderful pup, and I’m sure you did the right thing, and looking back, will not regret your decision. Peace to you.

  9. Andrea Phillips on March 17, 2019 at 4:14 am

    My 12 year old boxer has just had a subcutis hemangiosarcoma lump removed from near his spine. He went for ct scan which found a spleen mass had grown and appears different than when vet found it in December. She took FNA which came back as probable nodular hyperplasia. So was left. However has been very tired,thyroid was low but not hugely so so started on low dose of thyforon.then lump on his back started to change ,took FNA came back as blood so decided to have removed. Came back subcutis hemangiosarcoma. So removed and sent to referrels. He has now had a splenectomy as they felt the mass may burst.changes to his intestines but could not biopsy as felt was unsafe to do so. The mass was caviated and felt this was also hemangiosarcoma when removed. Now gone off for analysis. Bloods ok ish,liver values raised into the 200’s, which have been fluctuating for a year,WBC count low ,slightly, ….spleen changes compatible withliver disease but not cancer. He is still eating ,would this have in fact changed to cancer? Or was maybe the FNA incorrect of his spleen?

  10. Buddy John on March 13, 2019 at 1:00 pm

    These people are full of s h ! T ok, once your dog has gotten the lumps/cancer, you can spend tens of thousands of dollars (I know a lady fpent $40,000 dollarsnover 5yrs) the cancer will always come back. Nomatter how much surgery or how much money you throw at it, iv gone threw this twice in my 55yrs on this planet and emptied my bank account both times and maxed out mine & my wife’s credit cards. Doesn’t matter Cancer is 100% incurable in pets and they won’t tell you this bcuz there after “Your Money” they act like it’s all about your pet but b.s. it’s the money & you can believe me or not but see for yourself 1st hand then from then on keep your pet on fishmox (amoxicillin) you can buy from any feed store for hogs (animals) same exact stuff they prescribe to you for a tooth infection & made by the same pharmaceutical company 250mg x 2 in the morning and 2 at night, keep peroxide on hand & lesions clean, gov will live twice as long as vet treatments & be much happier/ playfull while saving you thousands. I kid you not.

    • Molly Jacobson on March 14, 2019 at 9:41 am

      Well, I don’t think I would keep my dogs on antibiotics every day, but I will say that there are hundreds of articles on this site designed to help people who want to help their dogs with cancer. Some want to break the bank, others want to focus just on quality of life. And that is exactly Dr. Dressler’s point: since there is no cure for systemic cancer (at this point) and you often find it way too late to address it (as he states very clearly above), everything is based on what is right for YOU and YOUR DOG. You can judge others for treating their dog’s cancer, but I’m going with Dr. D’s non-judgemental attitude. It’s a lot easier on me, and my dogs seem to be a lot happier, too. He says it best in this article:

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