Frequent urination (polyuria) goes hand in hand with frequent drinking (polydipsia). It isn’t a disease but a symptom of a medical problem. Polyuria is defined as the excessive production and elimination of urine and polydipsia is increased thirst.
Frequent urination differs from urgent urination in that the cat produces excessive amounts of urine whereas, in urgent urination, the cat may visit the litter tray frequently but only pass small amounts of urine and sometimes none at all.
Causes
There are many causes of polyuria/polydipsia in cats. Middle-aged to senior cats have a higher incidence of diabetes, kidney disease, and hyperthyroidism.
- Diabetes mellitus: Either caused by insufficient insulin secretion or insulin resistance.
- Chronic renal failure: Gradual loss of kidney function, which occurs most often in middle-aged to senior cats.
- Hyperthyroidism: Benign tumour of the thyroid gland which leads to the excess secretion of thyroid hormones. It occurs most in cats over 10 years old.
- Pyometra: Bacterial infection of the uterus of an intact female cat.
- Liver disease: Several diseases that damage the liver, preventing it from functioning properly.
- Cushing’s disease (hyperadrenocorticism).
- Hypercalcemia: High levels of calcium in the blood.
- Acromegaly: Excess of growth hormone in an adult cat, most often caused by a growth hormone-secreting pituitary tumour.
- Hypokalemia: Abnormally low potassium concentration in the blood.
- Psychogenic polydipsia: Compulsive water drinking with no physical cause.
- Medications such as diuretics which promote urination.
Note: Frequent passing of small amounts of urine either with or without straining can be due to a urinary blockage. This is a medical emergency and veterinary attention must be sought immediately.
Diagnosis
Your veterinarian will perform a physical examination of your cat and obtain a medical history including any medications your cat is on which could have resulted in this. He will palpate the abdomen to feel the size of the kidneys and liver, check for vaginal discharge and palpitate the thyroid gland.
Diagnostic workup:
Baseline tests: Biochemical profile, complete blood count, and urinalysis.
Diabetes:
- High blood sugar
- Ketones
- Glucose in the urine
- Low urine specific gravity
Liver disease:
- Hyperbilirubinemia
- Increased alanine aminotransferase (ALT)
Additional tests:
- Alkaline phosphatase test (ALP)
- Ultrasound to evaluate the liver
Kidney disease:
- Elevated blood urea nitrogen (BUN)
- Elevated creatinine
- Decreased urine specific gravity
- High phosphate in the blood (hyperphosphatemia)
- Ultrasound to evaluate the kidney
Low potassium in the blood (hypokalemia):
- Low potassium in the blood and urine
Acromegaly:
- High blood glucose (due to diabetes)
- High phosphorous
- Glucose in the urine
- Elevated liver enzymes (sometimes)
- High cholesterol
- Blood test: To evaluate increased plasma growth hormone or insulin-like growth factor 1 (IGF-1) for cats with suspected acromegaly
- CT scan: A definitive diagnosis of acromegaly is based on a CT scan which will reveal an enlarged pituitary gland
Cushing’s syndrome:
- Increased white blood cells
- Low calcium, elevated glucose and cholesterol
- ACTH stimulation test to measure the ability of the adrenal glands to respond to adrenocorticotropic hormone
- Urine Cortisol:Creatinine Ratio (UC:Cr): This tests levels of cortisol in the urine and is measured against levels of creatinine. If the level is normal, hyperadrenocorticism can be ruled out.
- Xrays or ultrasound to evaluate the adrenal glands.
Hyperthyroidism:
- Total T4 tests to look for elevated thyroid hormones in the blood.
- Ultrasound to evaluate the size and shape of the thyroid gland.
Pyometra:
- Ultrasound or x-ray of the uterus.
Psychogenic polydipsia:
- Water deprivation test to see if the volume of urine decreases, this can help to differentiate diabetes insipidus from psychogenic polydipsia. This test should only be performed on cats who are not dehydrated.
Treatment
- Diabetes mellitus – Dietary changes (low protein diet) and insulin (if required).
- Chronic renal failure – Dietary changes (low protein and phosphorous diet), phosphorous binders to manage elevated phosphorous levels in the blood, fluids (if dehydrated), anti-nausea medications and careful monitoring.
- Hyperthyroidism – Radioactive iodine, prescription diet, medications or surgery to remove the tumour.
- Pyometra – Antibiotics to treat the infection and removal of the uterus.
- Liver disease – Nutritional support, an anti-nausea medication. If the cause of liver failure is a portosystemic shunt, surgery.
- Cushing’s syndrome (hyperadrenocorticism) – Surgical removal of the affected adrenal gland (if an adrenal tumour is a cause), surgical removal of both adrenal glands (if a pituitary tumour is involved), gradual withdrawal of steroids if the cause is veterinary induced.
- Hypercalcemia (high blood calcium concentration) – Fluid therapy, loop diuretics increase calcium extraction from kidneys, steroids to decrease bone resorption, surgery to remove abnormal parathyroid gland (in primary hyperparathyroidism).
- Acromegaly – Management of symptoms, there is no cure for acromegaly.
- Hypokalemia – Treating the underlying cause, oral or intravenous potassium.
- Urinary tract infection – Antibiotics to treat the infection.
- Medications – Withdrawal or replacement where necessary.
In addition to specific treatments, the following may also be necessary:
- Supportive care such as fluid therapy for dehydrated cats.
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