How to Detect Canine Bladder Stones

Three Parts:Looking For Symptoms of Bladder IrritationLooking For Symptoms of a Blocked UrethraDiagnosing and Treating Canine Bladder Stones

To some people the idea of stones in a dog's bladder may seem a strange one. However these are not garden rocks, but mineral deposits that form in urine and stick together to form solid objects which physically resemble stones. The factors that cause a stone to form include the dog's genetic makeup, his diet, how much water he drinks, and health problems.

Part 1
Looking For Symptoms of Bladder Irritation

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    Understand that bladder stones have two phases. When they first form, they can rattle around inside the bladder like a stone in a tumble dryer and irritate the bladder wall.
    • Then, when the dog urinates the stone may pass out in a stream of urine or it may get stuck in the urethra (the narrow tube through which the dog passes urine) and cause a blockage.
    • This is serious because the dog is then unable to urinate, which causes back pressure on the kidneys and can lead not only to bladder rupture but also kidney failure.
    • Therefore, it's best to catch the early signs of bladder stones (such as bladder irritation) before the condition becomes more serious.
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    Watch out for blood-stained urine. Bladder stones rubbing against the delicate mucous membrane lining the bladder may cause it to become inflamed. When the bladder lining becomes inflamed it is prone to bleeding. This blood collects in the bladder and is passed out when the dog urinates.
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    Keep track of any recurrent urinary infections. An inflamed bladder has a weakened lining that is more vulnerable to infection. Many dogs with bladder stones get repeated urinary infections.
    • Although antibiotics clear the infection, if the underlying cause is still present i.e. trauma to the bladder lining, then it is likely to recur at a later date.
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    Consider whether your dog is urinating more frequently. Inflammation affects not only the mucus membrane lining the bladder, but the nerves in the bladder wall. The inflamed nerves send an incorrect message to the brain that the bladder is full and needs emptying. This may result in the dog repeatedly trying to pass water even though his bladder is empty.
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    See if your dog displays signs of discomfort when urinating. A dog with a sore bladder as a result of bladder stones will have discomfort when urinating. This may manifest itself as the dog looking wary as he passes water, or fidgeting, stopping mid-stream and seeking a new spot to lift his leg, as if the location is causing the problem.

Part 2
Looking For Symptoms of a Blocked Urethra

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    Be vigilant about signs of a blocked urethra. A bladder stone that blocks the urethra requires immediate veterinary attention. However, not all stones cause an obstruction, a lot depends on their size.
    • Stones that are smaller than the diameter of the urethra should pass out with no problems. Likewise, stones that are larger than the urethral diameter are too big to enter and hence cannot become stuck.
    • Unfortunately, there is a critical size when the stone fits into the urethra. It may then get trapped at anatomical narrowing where the urethra takes a U-turn around the brim of the pelvis, or at the penile tip. Both locations have a slightly reduced diameter and are a classic place for blockages to occur.
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    Look for non-productive urination. Like putting a plug in a sink, a trapped bladder stone stops the bladder from emptying out. Imagine the scenario where the sink taps are left running and the basin soon overflows.
    • The equivalent with the dog is the kidneys keep producing urine which fills the bladder. However, the bladder cannot overflow and so gets bigger and bigger.
    • He is desperate to urinate and either squats, of lifts the leg, but when you examine the ground it is dry.
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    Watch for repeated urinary straining. The dog, knowing his bladder is full, tries to urinate but nothing comes out. As the bladder gets fuller, his determination to urinate increases, but to no effect.
    • The dog becomes obsessed by trying to urinate, repeatedly moving from spot to spot and lifting his leg.
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    Take note if the dog is excessively licking his or her penile tip, vagina, or belly. Inflammation from the bladder lining can spread all the way down the urinary tract and some dogs lick their external genitalia in an attempt to alleviate their discomfort.
    • If the bladder is hard and full, this is very uncomfortable and the dog will sometimes lick his abdomen over the bladder in an attempt to find relief.
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    Examine your dog for abdominal distension. A large, hard bladder causes the dog's belly to distend. The bladder of a German Shepherd-sized dog can become football sized before it bursts, enough to visibly make his belly swell.
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    Seek immediate veterinary attention if your dog collapses. If the dog cannot void urine, the waste products of metabolism build up in the bladder and reflux back into the kidneys. Many of these waste products are toxins - potassium can be especially dangerous.
    • In blocked bladders, potassium reflexes into the blood stream and high potassium levels can irritate the heart muscle and cause heart attacks, often with fatal consequences.
    • Therefore if your dog collapses or you suspect his bladder has burst, it's essential that you rush him to the vets as quickly as possible.

Part 3
Diagnosing and Treating Canine Bladder Stones

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    Bring your dog to the vet for testing. If you notice any of the above signs then contact your veterinarian. In order to decide what the problem is she may request a urine sample for analysis.
    • The common tests done on urine are to measure specific gravity (how weak or strong the urine is), a dipstick test (which indicates if blood is present, checks for glucose, and protein content), and a sediment exam.
    • The most helpful exam in determining the presence of bladder stones is the sediment exam.
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    Understand how a urine sediment exam works. To prepare the sample, approximately 1ml of urine is put into a mini-test tube and spun down in a centrifuge. The heavy cells and sediment sink to the bottom under gravity.
    • The liquid above the sediment is removed and the debris at the bottom of the tube tapped out onto a microscope slide. A drop of saline is added to the sediment to re-suspend it and help it to spread in a layer one cell thick over the slide. This is examined at under the microscope.
    • The urine is examined for the presence of bacteria, red blood cells, renal casts, or crystals. Crystals are the precursors of bladder stones. It is unusual (but not impossible) for a bladder stone to form without crystals being evident in urine, and so their presence can be a warning sign of stones.
    • If sediment exam reveals the presence of crystals, and the dog has a corresponding history suggestive of bladder stones, (see signs above) then further imaging is required in order to check for stones.
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    Get a visual on the bladder stone using an ultrasound. The two options used to detect bladder stones are radiography and /or ultrasonography. However, not all types of stone show up on x-ray because their mineral composition is of almost identical radio density to urine. Thus, ultrasound is arguably the more reliable diagnostic test.
    • An ultrasound is a non-painful procedure which can be performed while the dog is conscious (in good-natured dogs). An area of fur is clipped from the area of the belly above where the bladder is located.
    • The skin is cleaned with surgical spirit and then a water-based acoustic gel applied to the skin. The ultrasound probe is placed against the skin, the abdomen is scanned and the bladder identified.
    • Fluid provides an excellent acoustic window for imaging, so when bladder stones block the passage of ultrasound waves, they create an "acoustic shadow". In real terms, this means there is a dark shadow on the far side of the stone, which can be seen regardless of the composition of the stone.
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    Understand the problems with radiography. The drawback to radiography is that not all stones show up. If the mineral composition is of similar density to urine, then the stone will be invisible on a plain x-ray (one where no contrast agent is injected into the bladder). This can give false negative results.
    • To avoid this, a double-contrast study may be done. This is where another agent, such as air, or a form of liquid barium, is introduced into the bladder. The aim is to provide material of a different radio density to urine, with the hope of showing up a stone.
    • Unfortunately, even with double contrast studies occasionally stones can hide and evade detection, so more and more ultrasound is replacing radiography to detect stones.
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    Be prepared for the possibility of surgery. Once a stone is found, the clinician needs to assess whether urgent action needs to be taken to avoid the risk of a urethral blockage. If this is likely, then surgery to remove the stone by colostomy (entering the abdomen and cutting the bladder open) is indicated, in order to get physical access to the stone and remove it.
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    Change your dog's diet to prevent the formation of new stones. Once removed, the stone is sent to a laboratory for analysis. This gives the exact chemical composition of the stone, which helps in selecting a diet that is low in the constituent parts, and thus reduces the risk of the dog growing more stones in the future.


  • There are many different types of urine crystals, each with a different mineral composition and a characteristic physical appearance. One of the most common is called struvite, which is made up of magnesium and phosphate, with a typical "coffin lid" appearance.


  • Mineral deposits form the urine because the body is a big chemistry set. A combination of the composition of the food and the minerals it contains, along with the body's biochemistry can result in crystals forming in the urine.
  • Another risk factor is if the dog does not drink a lot, his urine is more concentrated which means the minerals are in closer contact, and more likely to clump together.

Sources and Citations

  • Recurrent and persistent urinary tract infections in dogs. Norris, Williams, et all. JAAHA 36: 484-492
  • Textbook of Veterinary Internal Medicine. 7th ed. Ettinger & Feldman. WB Saunders.

Article Info

Categories: Canine Health