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Polyuria-Polydipsia (PUPD) In Pets

overview

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What is Polyuria & Polydipsia?

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Polyuria means increased urination, while polydipsia means increased thirst. We use the term PUPD to refer to a patient who is drinking and urinating excessively, as these generally go hand in hand. There are many causes of PUPD, as the body systems that control thirst and urination are highly complex. Finding a diagnosis takes time, and tests must be performed systematically to ensure nothing is missed.

Excluding very unusual conditions, possible causes for PUPD include:

• Kidney disease
• Liver disease
• Diabetes mellitus
• Cushing’s disease (dogs only)
• Pyometra (females only)
• Pyelonephritis
• Addison’s disease (dogs only)
• Hyperthyroidism (cats only)
• Hypercalcaemia
• Cancer
• Behavioural (e.g. stress, pain)

symptoms

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What are the symptoms of PUPD?

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Initially, signs of PUPD can be subtle. As it progresses, you may notice the water bowl is empty more often. Your dog may ask to go out more or your cat's litter trays may be wetter/need changing more frequently. Pets may be seen actively looking for water, such as drinking out of glasses or licking the taps. In older dogs, where the urinary sphincter is weak, PUPD may cause urinary incontinence. You may see symptoms due to the underlying disease process, such as weight loss or gain, change in appetite, vomiting, or changes to appearance.

diagnosis

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Which tests are used to diagnose PUPD?

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Initially, we must be sure that we are dealing with true PUPD. The easiest way to confirm this is to measure water intake over 24 hours. To do this, you can record how much water is offered and subtract the amount left in the bowl after 24 hours. Ideally, this should be measured for three 24-hour periods and an average calculated. Normal water intake varies with size, species and diet fed, so your vet can advise whether the amount recorded is significant.

A thorough history will help guide our diagnosis, including description of other symptoms, changes in the home environment, when the PUPD started, and the animal’s age, breed and neutering status. Clinical examination may highlight an area of concern, but can be normal. Several tests are likely to be required to narrow down possible causes:

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Blood tests

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General blood tests are used initially to screen for organ dysfunction and can rule many conditions in or out. Hormonal (endocrine) diseases are not identifiable on general blood tests and if these are suspected, often specific tests will need to be performed in addition. These may be a single sample, or stimulation tests; this is when a sample is taken before and after administration of a drug and the body’s response measured. Very commonly, multiple blood tests are required to achieve a diagnosis.

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Urinalysis

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In cases of PUPD, the concentration of the urine will be very low (referred to as the specific gravity) due to higher than normal water content. Urine is typically examined for abnormal molecules (such as blood, protein or glucose) and checked for infection. Some tests may need to be performed at an external lab. Occasionally, repeat urine samples are required to look for changes in the specific gravity through the day, or across several days.

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Imaging

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Some conditions that cause PUPD lead to physical changes to the organs. Imaging such as ultrasound, x-rays or CT scans may be required to examine the abdominal organs, heart or lungs.

outlook

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What is the outlook for pets with PUPD?

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Unfortunately, there is no quick fix for the excessive thirst and urination seen in these cases, and diagnosis can be a slow process. Although it can be tempting to limit water intake, it is important not to do this. Your pet relies on the additional water intake and can become very poorly if this is restricted. Try to offer more toilet breaks or litter trays, and consider putting puppy pads near the back door. Your pet may be as stressed by accidents as you are, so try to be patient.

Due to the huge variety in conditions that can cause PUPD, it is not possible to give a single prognosis. The majority of the conditions listed above can be treated, and some can be managed very successfully for many years. For most cases, PUPD can be investigated and diagnosed at your normal vets. If very specific tests are required, or a more unusual condition is suspected, referral to an internal medicine specialist may be advised.