Symptoms - Increased Drinking and Urinating

Question: Doctor

I have a spayed 17 year old cat (at least that old--she was adopted). Recently she began drinking copious amounts of water and urinating in her kitty litter box as well as in other areas of the house. My vet did blood work on her and can find no cause for this behavior. The values related to kidney health indicated a slight impairment but not enough to account for her excess drinking and urination. Nothing in the blood work indicated an infection or diabetes.

Any suggestions that might uncover her problem would be appreciated.

Thanks, Sue

Answer: Sue-

A general chemistry panel should eliminate several of the most common causes of increased drinking and urinating. Kidney failure, liver disease and diabetes mellitus should show up in lab work (or at least will most of the time).

Normal lab work might not show a problem with hyperthyroidism if a total T4 level is not part of the panel. Hyperthyroidism can cause increased drinking and urinating and is a common problem in older cats. Another potential problem is hyperadrenocorticism (Cushing's disease) which also has to be tested for with specialized tests. In cats, the high dose dexamethasone suppression test gives the most consistent results but isn't perfect. This condition is considered to be unusual in cats but does occur. Another unusual condition would be diabetes insipidus. It is best to rule out all of the above conditions prior to considering this one but if it is all that is left, using desmopressin (DDAVP Rx) to see if the cat will respond to treatment can be helpful in ruling out this possibility.

Dr Mike Richards, DVM 8/18/2001

Increased drinking and urinating

Question: Hi Dr. Mike:

I've been having a problem with my 10 year-old male neutered cat who has been drinking large quantities of water throughout the day and night. He's also very thin and has never gained any weight since I adopted him one year ago (approximately 8 lbs. and has an excellent appetite). He's a pretty large cat being half Main coon, but he's very thin). I brought him to a vet who did a CBC/SMA, blood glucose and T3/T4. The CBC/SMA was all normal (showing no kidney or liver problems), the blood glucose was at 80 (and he had eaten that morning), but his thyroid was a little high. They then did a Free T4 test which showed 5.5 (which they said was high). So I put him on Tapazole (5 mg 2 times a day) and after three weeks, his thyroid showed up very low (a reading of 3). So I was told to put him on 2.5 mgs of Tapazole once a day until he's tested again. But he's still drinking a heck of a lot of water. The vet did another blood glucose and SMA to check the kidneys again, but again everything showed up normal. The vet then said that it's possible he could have something called Diabetes Insipitus which is not life threatening and to let him drink all the water he wants. He also said he doesn't have the facilities to test him for this disease and to try to find a vet that does. Bu what I want to know is -- what exactly is Diabetes Insipitus and is it really not life threatening? I think the vet, at this point, is just guessing because he doesn't know what is wrong with him. I would really appreciate your advice in this matter as I'm at a loss as to how to help him and you have given me excellent advice in the past on my other cats.

Thanks

Dr. Mike.

Janice

Answer: Janice- There are a number of causes of increased drinking and urinating but the most common ones are diabetes mellitus (which has been ruled out), acromegaly (usually cats with this also have diabetes mellitus, so unlikely), hyperadrenocorticism (can occur without diabetes mellitus but is commonly linked with it), hyperthyroidism (present), kidney failure (doesn't show in lab work but might still be worth considering or watching carefully for), liver disease (not likely unless something shows in the lab work), behavioral or pyschogenic increase in water drinking and diabetes insipidus (uncommon to rare in cats but does occur).

Given this list, the three things that sort of stand out are hyperadrenocorticism, hyperthyroidism and diabetes insipidus.

Hyperadrenocorticism (Cushing's disease), is not very common in cats but it may be worth testing for. In cats, the high dose dexamethasone suppression test is considered to be the best test for this and any veterinary practice that uses an outside lab should be able to do this test.

Hyperthyroidism is present and it can cause increases in drinking and urinating. For some reason, this doesn't seem to go away fast, or sometimes at all, when we treat cats with methimazole (Tapazole Rx) even when it appears to be working well otherwise. We have only had a handful of cats have radioactive iodine therapy and I can't really remember whether we had the same problem with that, or not but I do think that this behavior does seem to respond to surgical removal of the affected thyroid gland so I'm thinking it should respond to radioactive iodine therapy, as well. So I think that this remains a possible cause of the increased drinking and urinating.

Sometimes cats with hyperthyroidism have kidney failure but not much change in their lab work to suggest it is present, so this is something else to think about in conjunction with the hyperthyroidism.

Diabetes insipidus occurs in cats but is uncommon. I think that your vet could test for this condition using Desmopressin ( DDAVP Nasal Spray Rx). Usually the nasal spray is transferred to a sterile ophthalmic dropper and 1 drop is put in the conjunctival sac (the area around the eye) every 12 hours. A generic product is available now, I think. The cost of the Desmopressin nasal spray inhibits some vets from prescribing it, so if there is a generic your vet might want to know about it, anyway. If there is a great improvement in the drinking and urinating behavior while on the medication, it is reasonable to presume that diabetes insipidus is present and to continue the medication.

It is true that strictly speaking it is not medically necessary to treat a patient with diabetes insipidus if they can free access to water and a litter pan. However, I do think it makes their life a lot better and so I would recommend treatment. It has to be uncomfortable to be thirsty all the time.

Just so that you understand this a little better, diabetes insipidus occurs for several reasons. There is a hormone, anti-diuretic hormone (ADH) that is secreted by hypothalmus in the brain which acts on the kidneys, causing them to concentrate urine. If the brain doesn't produce this hormone in adequate amounts (central diabetes insipidus) or the kidneys don't respond to the hormone (nephrogenic diabetes insipidus), then the pet can't concentrate urine. The kidneys then allow a lot more water through to the bladder and the pet has to urinate more. This means it has to drink more --- so the disease is characterized by increased drinking and increased urination. Nephrogenic diabetes insipidus can occur secondary to several conditions, including most of the list in the first paragraph. Many of these causes have been ruled out by the lab work so far, though. The central causes of diabetes insipidus result in altered kidney function that doesn't cause much harm, it is just uncomfortable and aggravating. I would want to treat this if I had it. The nephrogenic causes are best treated by finding the underlying cause and treating it, if possible.

I think I'd be tempted to hold off on trying to make a diagnosis of diabetes insipidus until you have good control of the hyperthyroidism. When that happens, if the increased drinking and urinating continue and you don't mind trying the Desmopressin eye drops, it seems reasonable to try this test to see if it is helpful. I think I'd probably want to test for hyperadrenocorticism prior to trying Desmopressin , but that is a judgment call and you and your vet may decide that isn't called for.

I hope this helps.

Mike Richards, DVM 8/5/2001