Increased Thirst and Urination: Important Clues for Medical Detectives

Increased Thirst and Urination:
Important Clues for Medical Detectives

By Ed Mapes
Stonebridge Animal Hospital
McKinney, Tx

The medical acronym is PUPD, short for polyuria/polydipsia; a condition in which the animal drinks more than normal and produces excessive amounts of urine. We as veterinarians are always on the lookout for these important symptoms in our patients because PUPD is present in many disease states – some of them very serious.
You may have noticed your veterinarian asking questions about thirst and urination whenever your pet is presented with a medical disorder. These signs often accompany a wide spectrum of other symptoms – vomiting, diarrhea, lethargy, decreased appetite, weight loss, weakness – and we strive to gather this patient history in efforts to formulate a diagnosis.

Our job is to take these bits of information from the history, combine them with lab data, and arrive at a diagnosis of the problem. Since our patients cannot tell us how they feel, where it hurts, or what might have caused the illness, we are very much like detectives working on a case.
We automatically begin to think in terms of beginning the process of excluding diseases from a long list of those that can cause PUPD. This scheme of inquiry is called an algorithm, and systematically crossing off disease possibilities allows us to hone in on one suspect as the cause. This list of diseases (Figure 1) is called our “rule out list”, and when we’ve determined that a certain disease can not be the cause of our patient’s symptoms, we “rule it out” as it’s removed from the list.

Addison’s syndrome Cushing’s syndrome
Diabetes mellitus Diabetes insipidus
Various kidney diseases Various liver diseases
Pancreatitis Severe infection
Forms of cancer Urinary bladder diseases
Psychogenic disorders Feline hyperthyroidism
Various skin diseases Hyperparathyroidism
Hyperkalemia Acromegaly in cats
Side effect of medications Tick-borne diseases

Figure 1 some of the possible diseases with PUPD as a symptom. We work our way through such a list, eliminating diseases until arriving at the diagnosis.

If a PUPD patient is also vomiting, has a slight fever, has lost her appetite and is listless, diabetes mellitus would be on our original rule out list on the algorithm. In this case one of the first and easiest tests we would run is a urinalysis. If this were to show no glucose in the urine, no ketones, and a normal pH of around 7.0, then we could assume that diabetes can be ruled out. Blood tests would confirm that suspicion with normal blood levels of glucose.

If we also determined that the dog was dehydrated, had a fever and elevations of the white blood cell level with a particular spike in the neutrophils and band neutrophils, we would lean more toward an infection being the culprit.

We notice on further blood testing that the liver and spleen appear to be normal, but see a slight elevation in blood protein and BUN – this bears out the presence of dehydration. We’re now able to cross out diseases of the liver, pancreas, and kidney, along with others on the rule out list.

When the owner states that the dog had been in heat one month prior to the onset of symptoms, we consider an infection of the uterus as the cause of symptoms. A vaginal swab confirms the presence of white blood cells in the thick, yellow fluid, and radiographs demonstrate an enlarged uterus – we have our diagnosis of an infection in the uterus and can now schedule a treatment plan: an intravenous catheter is placed and antibiotics are given, fluid therapy is begun to correct dehydration and correct acid:base imbalances, and the dog is scheduled for surgery to remove the uterus as soon as she is deemed stable enough for the procedure.

This case could have turned out to be any one of the disorders seen below, but without the important clue of PUPD to start our thinking toward those illnesses, diagnosis would have probably taken longer with a critical delay in appropriate care.
Increased urination can take the form of in-home accidents or crying to go outside at odd times or during the night – take note of this symptom because it may be polyuria.

Whenever your pet seems to drink more than approximately one ounce of water per pound of body weight per 24 hours, polydipsia may be present and could indicate an important illness. Either symptom signifies the need for a veterinary visit to begin the detective process and define a diagnosis.

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