Drinking and urinating more than normal is medically called polydipsia (poly = many; dipsia = drinking) and polyuria (poly = many; uria = urine). Thirst and urine production are a delicate balance controlled by interactions between the brain and the kidneys. Increased urination stimulates thirst, as the body’s overall hydration decreases and stimulates thirst mechanisms in the brain. Sometimes the opposite can be true when excess thirst triggers urination, as can be seen with diseases like diabetes when the body tries to dilute toxins by drinking more and the diluted blood then stimulates increased urination.
A rabbit with polyuria and polydipsia will have increased water intake and increased urine output.
The water bowl might become empty more frequently and there might be more instances of urine production; the urine might appear lighter in colour and less concentrated, or the rabbit may be partially incontinent.
On average rabbits will drink 50-150 ml/kg/day, so a large 5 kg rabbit will normally drink up to 750 ml each day, so anything over that could be abnormal. Similarly, normal urine production is about 120-130 ml/kg/day, so a large 5 kg rabbit will urinate as much as 650 ml per day, so anything over that may be abnormal.
The causes of polyuria and polydipsia can vary, but can include:
- Diabetes or insulinoma (a tumour of the pancreas)
- Renal (kidney) disease
- Hepatic (liver) disease
- Drugs, large quantities of sodium chloride
- Behavioural problems
Other conditions like dehydration can stimulate thirst, but if the rabbit is dehydrated it will usually have decreased urine production. Similarly, rabbits can have incontinence from things such as bladder stones or bacterial infections, or it might spray in territorial/behavioural display, but this doesn’t necessarily mean the rabbit is producing more urine.
Psychogenic polydipsia may lead to polyuria. The condition may be behavioural or due to a physical problem and can only be deemed a cause of polydipsia and polyuria once other causes have been ruled out.
Rabbits with dental disease may try to fill themselves up on water, if eating is too painful; the rabbit will drink excessively in an attempt to feel full, which in turn will lead to increased urination. These rabbits will lose weight, condition and appear miserable.
Bored, lonely or stressed rabbits may take comfort in drinking, especially from water bottles, as rabbits often like to ‘play’ with the ball-bearing in the tip of the bottle, leading to polydipsia and polyuria.
As there are many different causes for polyuria and polydipsia, your vet will need to thoroughly evaluate the clinical signs and carry out some diagnostic tests to narrow down the root of the problem.
Blood tests and urinalysis are the most common and will assess kidney function, liver function and the presence of excess blood glucose, as is frequently seen in diabetes. This can usually be done quickly with a day stay in hospital and results are usually back within a few days if samples are sent to an external laboratory.
If bladder/kidney stones are suspected, radiographs or ultrasonography might also be required. This usually requires sedation and a day stay in hospital.
Treatment of polyuria and polydipsia depends on the cause.
For diabetes, it is important to treat the underlying cause which may include weight loss.
For bladder stones, surgery and a change of diet may be needed.
For kidney and liver disease, the rabbit may need to be admitted to hospital for fluid therapy and supportive care as well as further investigations to determine if the condition is reversible.
The living environment of rabbits suffering from psychogenic polydipsia and polyuria will need a thorough review, a physical examination should also be performed to determine the cause and best course of treatment.
Each problem will need to be addressed individually.
To help prevent the incidence of disease that can lead to polyuria and polydipsia, ensure that the rabbit is happy and healthy. The environment should be safe, secure and non-stressful. Ensure the housing offers shelter as well as space where the rabbit can exercise and exhibit normal behaviour.
The rabbit’s water bowl should be large enough to provide at least the daily water requirement, and water should always be clean and fresh.
Food should be suitable and not contribute to obesity or bladder/kidney stones.
Provide environmental enrichment, such as places to hide, nesting material, toys to play with, wood for chewing, herbs to browse and soil to dig in.
Prevent overcrowded housing that can be stressful and promote unnecessary spread of disease. This includes reducing the likelihood of territorial aggression by avoiding housing the rabbit in close quarters with other that are un-neutered or of the same sex.
Ensure prevention of disease by having your rabbit seen at least once a year by your vet for an all over check-up and dental examination.
Provide rapid treatment of disease by consulting your vet at the first sign of any abnormal signs such as lack of appetite, changes in drinking or urination, changes in activity level, hair loss, scratching, excessive grooming, drooling, teeth grinding, changes in hair coat, faecal soiling, flystrike, limping, among others.