Understanding Cystine Bladder Stones in Dogs

Cystine bladder stones form when an amino acid called cystine builds up in your dog’s urine and crystallizes into hard deposits. It happens because of an inherited kidney defect that prevents cystine from being properly reabsorbed, and it’s a condition that tends to come back even after treatment. If your dog has just been diagnosed, understanding why this happens and what your options are is the best place to start.

What are cystine bladder stones?

Cystine is an amino acid (one of the building blocks of protein) that the kidneys normally filter out of the blood and reabsorb before it can accumulate. In dogs with cystinuria, the kidneys can’t do that job properly, so cystine passes into the urine in high concentrations. Over time, it crystallizes and forms hard stones in the bladder or urinary tract.

Cystine stones are less common than other stone types like struvite or calcium oxalate, but they tend to be more challenging to manage and are prone to coming back, even with treatment.

Symptoms of cystine bladder stones

The signs of cystine stones are similar to other urinary tract problems, which is why a proper diagnosis matters. Here’s what to watch for:

• Straining or difficulty urinating
• Frequent urination or accidents in the house
• Blood in the urine
• Licking at the genitals
• Crying out in pain while urinating

In male dogs especially, a complete inability to urinate can signal a urethral obstruction; a life-threatening emergency. If your dog is straining without producing urine, restlessly pacing, or crying out, get to a vet immediately. This can’t wait.

Common causes and risk factors

Cystine bladder stones are caused by an inherited condition called cystinuria, where the kidney tubules can’t properly reabsorb cystine from the urine. The genetics behind cystinuria vary by breed; in Newfoundlands, for example, it follows an autosomal recessive pattern, meaning a dog needs to inherit the defective gene from both parents to be affected. In other breeds, the inheritance pattern may differ, and your vet or a veterinary geneticist can help clarify what that means for your dog specifically.

Male dogs are more commonly and more severely affected than females. This is largely because the male urethra is longer and narrower, making it much easier for stones to cause a blockage.

Breeds with a documented higher risk include:

• Newfoundlands
• Scottish Terriers
• English Bulldogs
• Basset Hounds
• Mastiffs
• Dachshunds
• Irish Terriers
• Chihuahuas

In rare cases, cystine stones can also form secondary to a portosystemic shunt; a liver condition where blood bypasses the liver and isn’t properly filtered, leading to abnormal amino acid levels in the urine.

Diagnosing cystine stones

Your vet will likely start with a urinalysis to look for cystine crystals in the urine. From there, additional diagnostic steps may include:

• Ultrasound imaging: The most reliable way to visualize cystine stones, since they are only weakly visible on X-rays
• X-rays: Sometimes used but less definitive for this stone type
• Cystoscopy: A small camera used to examine the inside of the bladder and urethra
• Stone analysis: When a stone is retrieved, laboratory analysis confirms it’s cystine and rules out other types
• DNA testing: Available for some breeds with known genetic markers for cystinuria

Knowing the size and location of the stones is important before deciding on a treatment approach.

Treatment options for cystine stones

Treatment depends on the size and location of the stones, and whether they’re causing an obstruction. Here’s what’s typically available:

Dissolution through medication

Medications like tiopronin (2-MPG) work by binding to cystine in the urine, making it more soluble and preventing new crystals from forming. D-penicillamine works through a similar mechanism but tends to cause more side effects and is less commonly used today. Dissolution is a slow process, it can take weeks to months, and requires regular monitoring.

Specialized diets

A low-protein, low-methionine diet helps reduce cystine levels in the urine. Methionine is an amino acid that the body converts into cystine, so reducing it in the diet means less cystine reaching the kidneys. Alkalinizing supplements like potassium citrate are often added to increase urine pH, which makes cystine more soluble and less likely to crystallize.

Surgical or minimally invasive removal

If stones are too large to dissolve, or if they’re causing a blockage, your vet may recommend surgical removal (cystotomy) or laser lithotripsy, a procedure that uses a laser to break stones into small enough fragments to be flushed out or retrieved. This is typically done under anesthesia with a small camera passed into the urinary tract.

Managing obstructions

For male dogs with urethral obstruction, emergency catheterization may be needed to relieve the blockage first, followed by stone removal or dissolution once the dog is stable.

Preventing recurrence and long-term care

Cystine stones have a high recurrence rate, so ongoing management is a real part of life with this condition. That typically includes:

• Staying on a vet-prescribed diet long-term
• Continuing prescribed medications as directed
• Regular urine testing to monitor cystine levels
• Routine vet check-ups to catch any new stone formation early

Recurrence can be frustrating, but consistent monitoring means you’re much more likely to catch new stones before they become a bigger problem.

Is it covered by pet insurance?

Yes, cystine bladder stones are covered under Lemonade Pet’s base accident and illness policy, as long as the condition isn’t pre-existing. That includes eligible costs like diagnostic testing, medications like tiopronin, surgical removal, and emergency care if an obstruction occurs.

One thing worth knowing: prescription food isn’t covered under Lemonade’s policy, even when it’s part of a treatment plan. The specialized diet used to manage cystine stones will be an out-of-pocket cost to factor in alongside your coverage.

As with most conditions, getting a policy in place while your dog is symptom-free is the clearest path to making sure you’re covered. Once signs appear, the condition is typically considered pre-existing and won’t be eligible for coverage.

Before we go

Cystine bladder stones are frustrating to manage, partly because recurrence is so common. But consistent monitoring, staying on top of medications, and working closely with your vet make a real difference in catching new stones early before they become a bigger problem. It’s an ongoing commitment, but one that’s very manageable with the right plan in place.

If you don’t have a pet insurance policy yet, now is a good time to explore your options. Getting a quote takes just a few minutes, and having coverage in place before any symptoms develop puts you in a much stronger position when it matters most.

Frequently Asked Questions

A few quick words, because we <3 our lawyers: This post is general in nature, and any statement in it doesn’t alter the terms, conditions, exclusions, or limitations of the policies issued, which differ according to your state of residence. You’re encouraged to discuss your specific circumstances with your own professional advisors. The purpose of this post is merely to provide you with info and insights you can use to make such discussions more productive! Naturally, all comments by, or references to, third parties represent their own views, and Lemonade assumes no responsibility for them. Coverage may not be available in all states. Please note that statements about coverages, policy management, claims processes, Giveback, and customer support apply to policies underwritten by Lemonade Insurance Company or Metromile Insurance Company, a Lemonade company, sold by Lemonade Insurance Agency, LLC.  The statements do not apply to policies underwritten by other carriers.