Bladder Stone - What's the big fuss?!

Hi everyone

so this post is going to be about bladder stones, this is relevant for any species from dogs, cats and even guinea pigs.  For this post we will focus on dogs and cats. We'll talk about what they are, how they develop, symptoms and how to deal with them... enjoy!!!

Lets start with what they are and how they develop;

Bladder stones are the accumulation of microscopic mineral crystals that are present in the urine, that along with a mucus like substance produced by the bladder build up and stick to each other growing and growing over time.  The correct name for bladder stones are uroliths. 

Different uroliths develop in urine of differing PH levels, some favour acidic conditions and other alkaline. 

The most common crystals found in dogs are;

- Struvite uroliths (magnesium ammonium phosphate or MAP)

- Urate uroliths 

- Cystine uroliths

- Calcium oxalate uroliths

If left untreated they will eventually reach a size that is visible to the naked eye and some to the size of say the stone in a plum!!! Some of you may remember this picture from one of our "What is it Wednesday's" of some bladder stones that were surgically removed from a dogs bladder.

So why are they so dangerous? 

There are many answers to this question but the main reasons are as follows;

1. These stones are rough and hard and they move freely around in the bladder, this scratches and traumatises the lining of the bladder which causes bleeding, inflammation and pain.

2. These can also get lodged in the urethra (the tube that carries urine from the bladder to the outside world). This not only causes pain and trauma but can actually block the urethra meaning that it is impossible for the patient to pass urine either at all or only be able to pass small amounts.

What do you think happens when the bladder is unable to empty? 

The kidneys continue to produce urine and the bladder continues to fill meaning that in extreme cases it cannot take anymore urine, to the point that the bladder bursts like a water balloon. I'm sure you can imagine that repairing a ruptured bladder is not an easy task and the risk of infection is very high.  Unfortunately if the bladder does rupture there is a high chance it will prove fatal for the patient.

If the bladder doesn't burst you still have urine backing all the way up the urinary tract, right back to the kidneys which can cause the kidneys to fail further adding to the patients complications.

What causes bladder stones... 

The pH level of a substance tells us how acidic or alkaline it is and depending on these conditions we either have a normal or abnormal environment. When the environment is normal we don't get the development of these crystals (but be aware of calcium oxalate crystals).  When it's abnormal it creates the perfect development site for them.

Some crystals only develop in acidic urine and others in alkaline,  for example calcium oxalate loves an acidic urine but they can also develop in neutral urine!!!, whereas triple phosphate AKA struvite crystals adore an alkaline urine.  There are other crystals too including; cystine, ammonium urate (Dalmations are prone to these), uric acid, calcium phosphate and calcium carbonate but the two most common we see in our practice are struvite and calcium oxalate. 

Diagnosis -

When we perform a urine analysis we also perform a 'dipstick' which indicates the presence of; glucose, bilirubin, ketones, blood, protein, pH, uroliths and leucocytes. We then check how concentrated it is using an instrument called a refractometer - this gives us an idea of how well the kidneys are functioning.  Again you may remember this picture from another What is it Wednesday...

Refractometer view

Once all this is done the vet will review the results and based on these as well as the patients clinical exam or symptoms described by the owner we will decide if a urine sediment should be examined under the microscope.

To perform a urine sediment we take a small sample of urine and spin it down in the centrifuge at a speed of 1500rpm for 5 minutes. The result is a separation between the urine at the top of the sample and the sediment at the bottom. We take a sample of the sediment, this is done my removing the upper layer of urine, adding a drop of sedistain and then re-mixing the sediment. With a pipette we then suck up the remaining fluid and put a drop on a microscope slide and then cover with a very thin, glass cover slip. It is now ready to examine under the microscope.

Below are photos taken of a patients urine sediment.  When we request a urine sample from your pet this is one of the test that we do.  We centrifuge a sample of the urine, this sends all the "hard" particles to the bottom of the sample which we pipette out and examine under the microscope.

Struvite

Calcium Oxalate

As well a urine crystals we may also see red blood cells, casts and white blood cells.

If there are crystals present we now need to diagnose if they have yet formed stones which can be done by ultrasound examination of the bladder although this isn't 100% accurate so ideally x-rays and sometimes contrast x-rays should be used... See pictures below.

Large Bladder stone almost filling the bladder

Bladder stones in a Guinea Pig

If stones are present we need to be looking at removing them surgically and if they have not yet developed we need to do everything we can to keep it that way.

Prevention -

We need to change the pH of the urine, this is achieved through a diet change and we recommend Royal Canin Urinary prescription food which will dissolve the existing microscopic crystals and any tiny stones. We will need to keep a close eye on the patients urine, so regular dipstick and sediment rechecks will be done.

When feeding this prescription food it is important that no other food is fed - including treats, as it will instantly alter the pH of the urine and undo all the good work of the prescription food.

We don't charge to test your pets urine and we recommend you bring a morning sample to their booster appointment where a routine dipstick test can be performed if you wish.

Now go and share your new found knowledge and pictures with your friends :)