| PU/PD: Pets Drinking Too Much Water |
There have recently been a few posts on increased water consumption in
both dogs and cats so I thought I would write a small crash course
lecture on it. So if you are ready, or just can’t sleep, here we go!
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| My pet drinks a lot of water. That’s good right? |
 Not always. In fact, if it is noticeable or the increase in urination
is greater in amount then there may very well be a problem. Increased
water consumption or increased urination is call PU/PD or
PolyUria/PolyDipsia in the medical realm. Remember what goes in must
come out – so increased thirst and increased urination are linked.
Occasionally some medical source will sublist the causes as those that
cause primary increased thirst with secondary increased urination and
those that cause primary increased urination with secondary increased
thirst. Usually these are all lumped together since most are a primary
increase in urination. Why does this occur? Simply, because the kidneys
cannot concentrate the urine so the urine isothenuric, that is the same
concentration as the blood. So if my pet has PU/PD then, it must have
kidney disease? No. While it is from inability to concentrate, many
other factors can influence normal kidneys into PU/PD.
So what causes PU/PD. Usually you will hear vets, and myself, talk
about the twelve causes of PU/PD. While this is a wonderfully biblical
number, it is an oversimplification. A list which appears below,
complied by Dr. Kathy James, lists a more complete 15 causes. If we
look at the most common causes, then twelve usually works well. Also
dogs and cats have some causes which are the most common.
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| Most common Causes – top five |
 Dogs: Diabetes Mellitus, Kidney disease, Kidney Infection, Liver Disease, Cushing’s diseas
 Cats: Kidney disease, Diabetes mellitus, Hyperthyroidism, Kidney infection, Liver disease
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| Complete list for dogs and cats compiled by Dr. Kathy James from VIN, the Veterinary Information Network at U.C.Davis. |
(some of these have some major nerdy medical terms ,
I included this for completeness and to show how complex this can be. I
reduced the terms to English only briefly or not at all so this would
stay only a thread and not turn into a sweater! )
1. Hyperadrenocorticism (Cushing’s disease)
2. Hypoadrenocorticism (Addison’s disease)
3. Hypercalcemia (high blood calcium)
4. Diabetes mellitus (basic diabetes that most people are familiar with – high blood sugar)
5. Hepatic disease (Liver disease)
6. Pyelonephritis (kidney infection)
7. Leptospirosis (bacterial spirochete infection of the kidneys – a tropic and subtropic disease)
8. Chronic Renal Disease/Renal Failure (May be present without any blood laboratory changes)
9. Hyperthyroidism (over active thyroid, similar to Grave’s disease in
people (John Adams was thought to have this disease). It is rare, very
rare in dogs)
10. Hypokalemia (Low blood potassium)
11. Pyometra (infection of the uterus)
12. Renal Tubular Diseases (in basenji’s it is called Fanconi’s Syndrome)
13. Chronic Partial Urinary Obstruction or Post-Obstructive Diuresis
(urethral obstruction, like a urinary stone lodged in the penis –
common in cats)
14. Iatrogenic (caused by human intervention, either therapeutic or
not) Disease due to medications such as lasix (diuretic commonly used
in heart failure management), phenobarbitol (used to control seizures)
ot diets too high in salt or heavily restricted in protein.
15. Pheochromocytoma (unusual intra-abdominal tumor of the adrenal gland)
16. Polycythemia (condition where too many red blood cells are made)
17. Acromegaly (usually have concurrent diabetes mellitus)
18. Paraneoplastic syndromes (syndromes created by the affects of cancers)
19. Pericardial Effusion (fluid accumulation in a sac that envelopes the heart)
20. Psychogenic Polydipsia (as in a true behavioral disorder with a compulsive element)
21. Primary Non-Medical Polydipsia (AKA “I drink a lot because I like
it or I engage in activities that promote it, but that doesn’t mean I’m
sick”)
22. Primary Nephrogenic Diabetes Insipidus
23. Hypertension
24. Atypical Cushing’s and SARDS
25. Central Diabetes Insipidus
Whew!!! What a list. Thanks again Dr. James.
Luckily we rarely have to go down the whole list. Often the cause PU/PD
will be picked up with initial blood and urine testing, plus or minus a
few additional tests.
On occasion initial testing will be negative and then the diagnostic
work up becomes a little more challenging as the list would indicate.
So if this happens, give you vet some slack – it may take a bit to diagnose.
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| How do I know if my pet drinks or pees too much?? |
PolyDipsia is defined as the consistent drinking of more than 100ml of
water per kilogram of weight per day (>100mls/kg/day). PolyUria is
defined as the consistent urination of more than 50ml of water per
kilogram of weight per day (>50mls/kg/day). If you need help with
the conversion of ml/kg/day – let me know I can make a new thread or we
can do it by PM). Also you will notice that only half the water drank
comes out as pee. Where did that other 50mls go? Insensible losses such
as with stool, sweat, evaporation, tears, etc…
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| Why test, there isn’t anything I am going to do about it anyways? |
While probably anybody that is still ready this, would never say this
question, I get it a lot. So if you hear someone say it – this is what
you can tell them. While these conditions may start out as just
increased water consumption most will lead to severe, if not life
threatening complications.
Early detection can improve survivability, improve chances for a cure
(if the disorder is curable such as infections), give the pet longer
life expectancy, allow easier management and be less cost to the owner.
This is a win-win solution!
Early detection is the key. Also many of these conditions, even if not
curable, can sometimes be simple and straight forward to manage early.
For example, non-infectious kidney failure patients can have their life
expectancy doubled by simple diet change. Pretty straight forward huh? 
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| How else can I be proactive? |
Yearly blood and urine testing , especially on those dogs older than
seven and cats older than ten. If younger – perhaps every other year.
If funds are on the watch and we are only looking at PU/PD – then
consider just a urine sample. If the urine is concentrated and
otherwise normal, we have eliminated 25 diseases in one swoop! Wooohoo.
Urine that is collected first in the morning is best because it has the
best chance of being concentrated.
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