The following are real life cases of Increased Drinking and Urinating in Dogs that have been treated by Dr. Mike Richards, DVM.
Wilma, my 7yr. female Dalmatian has gained 10 pounds in two months, drinks a large amount of water and pants. Her vet ran the ACTH test for Cushings. Negative. Urinary infection and diabetes also negative. What are your recommendations?
There are more than 20 disorders that can lead to increased drinking and urinating. It can be frustrating to sort through them all but the only thing that you can do is to start somewhere, as you have done, and eliminate the disorders until you find the one that is causing the problem. The list of disorders I can think of that cause increased drinking include:
- kidney failure (chronic, acute, infectious (leptospirosis, esp.))
- hyperadrenocorticism (Cushing's disease)
- diabetes mellitus
- liver failure
- hypoadrenocorticism (Addison's disease)
- pyometra (uterine infection, applies to females only, obviously)
- intestinal obstruction (occurs after toxins begin to be absorbed from the damaged intestine)
- pyelonephritis (infection of the kidney)
- hypercalcemia (most commonly from cancer)
- diabetes insipidus -- can be central (brain related) or nephrogenic (kidney related)
- behavioral or psychogenic water drinking
- renal glycosuria (Fanconi's syndrome)
- partial obstruction of the urinary tract
- neurologic damage leading to urine retention or difficulty voiding
- medications (diuretics, corticosteroids)
- pheochromocytoma (a form of cancer)
- pericardial effusion
- hypothyroidism (dogs) or hyperthyroidism (cats) -- not too common with these
- paraneoplastic syndromes (usually this is hypercalcemia but sometimes other substances linked to tumors cause increased drinking)
Diagnosing the Cause of Increased Urination and Thirst
Most of the time a number of these conditions can be eliminated based on the physical examination and initial blood chemistry panel, urinalysis and complete blood cell count. That usually leaves the hormonal disorders and psychogenic causes, plus some of the rare conditions like pheochromocytomas.
The hormonal illnesses can be tested for individually. Determining the right order to test for them is difficult and is often a judgement call. We usually start with Cushing's disease if we have no idea which illness seems most likely based on our initial findings and tests. We do this just because it is a common cause of increased drinking and urinating (and weight gain). Acromegaly is normally associated with diabetes so we may skip testing for this one in the absence of diabetes unless we don't find anything else. Hypoadrenocorticism is less common than Cushing's disease so we usually test for it second and often only if the cortisol levels were low on the samples taken for the Cushing's disease testing. Diabetes insipidus is most easily tested for clinically by judging response to treatment using desmopressin (DDAVP Rx).
It can take some time to sort through these possibilities but with persistence it is usually possible to find a cause for the increased drinking and urinating. It is sometimes necessary to test for Cushing's disease several times in dogs with strong clinical signs but normal test results -- there are false negative test results between 5% and 25% of the time (percentage varies depending on which studies you read and which tests are run).
Increased Drinking, Urinating and Appetite - Is it Acromegaly?
Well, after a lot of testing and ups and downs, my veterinarian thinks my dog has acromegaly. Acer is a chocolate lab, about 5 years old, who has the following clinical signs: polydipsia, polyuria, polyphagia, heavy in the trunk, short in stature, large head and paws. We pursued Cushings disease for a long time because he had high Alkaline phosphatase, low BUN, high cholesterol and low specific gravity of the urine.
Then, we did a cortisol/creatinine ratio which came up at the high end of the normal range (I think it was 23). We were puzzled, but decided to do the low dose dexamethasone suppression test and the bile acids test, which both came back normal today. Now, my vet says that the only thing they can do is a serum assay for an insulin-like growth factor, which she thinks might confirm the diagnosis of acromegaly.
She says that at the University vet school, they could do a creatinine clearance test to check on the function of his kidneys, and they could also do a CT scan of his brain to look for the pituitary tumor that she thinks is probably there.
I would greatly appreciate it if you could tell me some more details about this and what the prognosis is. My vet said that acromegaly is not treatable, but that it may be worthwhile to look for a kidney problem or for central diabetes insipidis, which may be treatable. I really like Acer -- he is a very sweet dog, but I don't want to spend any more money for tests if there is very little chance of finding anything treatable.
His excessive drinking and urinating are annoying, but the symptom that bothers me the most is how hungry he is all the time. I can see how hard it is for him to relax when he is so hungry, thirsty and needing to pee. Do you have any advice or information for me?
I have to apologize in advance for the answer to this question. I am nearly certain that it is going to raise more questions than it answers. However, I only know one way to approach a patient whose primary problem is increased drinking, increased urinating and increased appetite and that is to rule out the most common causes of these conditions, one by one, until an answer is found or until I am forced to make my best guess as to the diagnosis because I have reached the point where I have ruled out all the things that the owner can afford to test for or is willing to test for.
These are the things that can cause increased drinking and urinating in dogs that I can think of. There are probably a few more, but this is a pretty complete list:
diabetes mellitus (the common form of diabetes) diabetes insipidus central diabetes insipidus (caused by brain tumors) nephrogenic (kidney damage leads to it -- pyelonephritis, pyometra (uterine infection), etc. chronic kidney failure (glomerulonephritis, amyloidosis) hyperadrenocorticism (Cushing's disease) hypoadrenocorticism (Addison's disease) hypercalcemia (usually due to metastatic cancer when seen in dogs) hypothyroidism Fanconi's syndrome (renal glycosuria) liver diseases hypokalemia (low potassium levels in the blood stream) medication induced (glucocorticoids, diuretics, sometimes as an adverse reaction to other meds) polycythemia (increased red blood cell numbers) behavioral (sometimes referred to as psychogenic diabetes insipidus) leptospirosis urinary obstructions -- can be partial and have a long course before causing really severe problems intestinal blockages (usually there are LOTS of other signs to indicate a severe problem in this case) phenochromocytomas acromegaly
So the trick is to sort through all these possibilities as efficiently as possible and then to treat whatever is found. Some things are easy to eliminate, such as pyometra (uterine infection) since Acer isn't likely to have this problem being male. The rest of the list is much much harder to work through. A good general chemistry panel is a good idea and you have done that. Unfortunately, normal lab values do not rule out kidney problems, liver problems or any of the disorders that require more specialized testing.
The most useful test that you haven't done, at this point, would probably be an abdominal ultrasound examination, since it would help to rule out liver disease, kidney disease, hyperadrenocorticism, cancers and partial obstructions in the ureters, bladder or urethra.
The high alkaline phosphatase and low BUN in combination is suggestive of liver disease. It is not too expensive to run a bile acid response test to try to further rule out liver disease as a contributing factor, especially if an ultrasound examination indicated potential problems. A liver biopsy might be necessary to confirm the type of liver disease present but it is usually possible to help some and often to help a great deal with liver disease.
Ruling out Cushing's disease was a good idea. I have had three or four patients over the twenty-two years I have been in practice who have had Cushing's disease who had two or three low dose dexamethasone suppression tests (LDDS) come back normal before being able to confirm the disease and have had one patient we finally treated based on clinical signs who responded really well to treatment, making me think that she had the disease without any sign on either LDDS or ACTH response testing. Acer is pretty young for Cushing's disease, though. So I would tend to believe the test results and just keep it in the back of my mind that Cushing's disease is not totally ruled out by them.
Hypothyroidism is common in Labs and it is pretty easy to test for. I like the free thyroxine (Free T4) test by equilibrium dialysis best. I think of leptospirosis as an acute illness but it can apparently cause more chronic illness in some dogs without having much of an acute phase. Titers can be measured for this but I have to admit that if I was choosing tests based on a cost efficiency basis I wouldn't do this test in a dog with a long standing history of PU/PD behavior and no strong reason to make me suspect it.
Hypoadrenocorticism is usually associated with decreases in appetite, or variable appetite and sometimes GI signs like vomiting or diarrhea. It is not an especially common problem but it is easy to overlook. The resting cortisol level on the LDDS test would help to rule this out. If it was in the high end of normal it would be more unlikely that it is just based on prevalence.
Think about medications. If you aren't using any, that is easy to rule out. Fanconi's syndrome should cause sugar to be present in the urine. If not, then it isn't likely. Hypercalcemia is usually ruled out as calcium is included in many blood panels.
Psychogenic polydipsia is hard to rule in or rule out, for me. If this is the case it should be possible to distract the dog from the behavior by doing things like taking a trip to a nature trail or big park and playing with the dog to see if that distracts it from the water drinking behavior. Even boarding a dog will sometimes work to help see if this is the problem since many dogs find this to be very distracting and may be reluctant to drink water at a kennel or veterinary hospital unless they are really driven to do so. This has to be done carefully, though. A dog that really does have diabetes insipidus can get dehydrated pretty rapidly and the dehydration can be fatal if water is not available.
About this point I'd start thinking about central diabetes insipidus and acromegaly since they are not very common in dogs. If central diabetes insipidus is present the thirst is usually extremely problematic. One of my own dogs had central diabetes insipidus and she was obviously "water starved" -- the thirst was very compelling to her. In addition, she also had weight loss and then neurologic signs associated with the brain tumor leading to the disorder. Some dogs do have thirst that is not quite so driving a force in their lives and neurologic signs are not always present. The urine specific gravity should stay below 1.010 and usually below 1.007 when diabetes insipidus is present.
Acromegaly due to pituitary tumors would have to be considered a very rare disease in dogs, based on the literature. I can only find a couple of case reports of this condition and most of the textbooks don't really discuss it at all. A study from 1996 (van Keulen et al), says that acromegaly as the result of pituitary tumors has not been demonstrated to occur in dogs but this may have changed in the last few years. In dogs, the excessive growth hormone is usually produced by mammary gland tissue when acromegaly occurs and it is usually produced as a side effect of the use of medications with a progesterone effect, such as megestrol acetate. If this is the cause, stopping the medication is usually curative.
I think that the odds of finding a problem that might respond to therapy are still high for Acer. However, it may be hard to find that problem without doing a lot more testing. I think that it might be worthwhile to ask your vet about referral to an internal medicine specialist who can do the ultrasound examination (or a vet with a strong interest in this in your area) because that would also get you a second opinion from someone who can see and evaluate Acer. You might want to think about the possibility that this is behavioral and try to figure out a way to test that theory prior to going through a lot more testing but it may be hard to prove that a behavioral problem is the cause, or to rule it out completely.
I know this was a long reply and that it covered a lot of ground. Please feel free to write for clarifications if it has been confusing.
Michael Richards, D.V.M. co-owns a small animal general veterinary practice in rural tidewater Virginia. Dr. Richards graduated from Iowa State University's College of Veterinary Medicine in 1979, and has been in private practice ever since. Dr. Richards has been the director of the PetCare Forum...