Straining to urinate, frequent small urinations, and blood in the urine are common clinical presentations in dogs. When abdominal imaging reveals a bladder stone (urolith), pet owners and veterinary teams face a critical series of decisions.

Can the stone be dissolved with a change in food, or is surgery required? How urgent is the condition, and how can we prevent new stones from forming?

This clinical guide provides an in-depth analysis of canine urolithiasis (bladder stones). We will examine the distinct mineral compositions of stones, evaluate the medical dissolution pathway versus surgical removal, review the latest prevalence statistics from the Minnesota Urolith Center, and lay out evidence-based protocols to manage and prevent recurrence.

Scenario Question

My dog was diagnosed with a bladder stone after showing blood in her urine and straining to pee. The veterinarian took an X-ray and suggested we might need surgery, but also mentioned a special diet. Can bladder stones in dogs be dissolved with food, or is surgery always required? How can I stop them from coming back?

Direct Answer

Whether a bladder stone can be dissolved with food depends entirely on the mineral type of the stone. Canine bladder stones are not all the same: struvite stones (magnesium ammonium phosphate) are frequently dissolvable using a therapeutic prescription diet (often paired with antibiotics if a urinary tract infection is present), but calcium oxalate stones cannot be dissolved by any diet or medication and must be physically removed, either surgically or through non-surgical flushing.

To determine the mineral type, a veterinarian must analyze the stone itself once retrieved, or infer the type using a diagnostic combination of urine pH, crystalluria, breed predisposition, and radiopacity on X-rays. In a male dog that is straining and unable to pass any urine, a stone may have become lodged in the urethra, creating a life-threatening urinary obstruction emergency that requires immediate veterinary intervention regardless of the stone type. The two minerals dominate: in the Minnesota Urolith Center's 2023 global data (about 63,762 canine submissions), struvite is the most common canine urolith (roughly 41%), with calcium oxalate second (roughly 33%) — though the two have traded the top rank back and forth over the past two decades. Preventing recurrence requires a tailored approach based on the specific stone mineral, focusing on high hydration, urine pH management, and target diets.

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What bladder stones are, and why the mineral type decides everything

Canine urolithiasis refers to the formation of macroscopic mineral concretions, or uroliths, anywhere within the urinary tract, most commonly in the urinary bladder. These stones develop when the urine becomes supersaturated with specific mineral ions, causing them to precipitate out of solution as microscopic crystals. Over time, if the physical and chemical conditions in the bladder allow, these crystals aggregate, bind together, and grow into solid stones.

The distinction between urinary crystals (crystalluria) and bladder stones (urolithiasis) is clinically important:

• Crystals are microscopic structures. The presence of crystals in a urine sample does not automatically mean a dog has or will develop bladder stones. Many healthy dogs have transient crystalluria that causes no clinical signs.
• Stones are macroscopic structures that can cause physical irritation to the bladder wall, lead to secondary bacterial infections, and physically block the flow of urine.

The chemical composition of the stone decides the entire treatment pathway. The main minerals that form uroliths in dogs are:

1. Struvite (Magnesium Ammonium Phosphate): The most common type in recent Minnesota Urolith Center global data, and historically dominant as well. These stones are highly associated with urinary tract infections in dogs.
2. Calcium Oxalate: The second most common type in recent Minnesota Urolith Center global data, though it was the leading canine stone type for much of 2004–2018. These stones form in neutral-to-acidic urine and do not respond to medical dissolution.
3. Purines (Urate): Associated with specific breed genetics and liver dysfunction.
4. Cystine: A rare type caused by an inherited renal transport defect.

Because each mineral precipitates and dissolves under completely different chemical conditions, a veterinarian cannot treat "a bladder stone" as a single disease. Identifying the stone type is the first and most critical diagnostic task.

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The urology matrix: canine bladder stone types and characteristics

To guide diagnostic and therapeutic decisions, the following matrix compares the four primary urolith types encountered in dogs:

Characteristic	Struvite	Calcium Oxalate	Purine (Urate)	Cystine
Chemical Composition	Magnesium ammonium phosphate hexahydrate.	Calcium oxalate monohydrate or dihydrate.	Ammonium urate, sodium urate, or uric acid.	Cystine (sulfur-containing amino acid).
Relative Prevalence (2023 MUC)	~41% of canine uroliths.	~33% of canine uroliths.	~5% of canine uroliths.	~7% of canine uroliths.
Dissolution Potential	Highly Dissolvable (diet + infection control).	Not Dissolvable (requires surgery/flushing).	Sometimes Dissolvable (diet + allopurinol).	Difficult to Dissolve (diet + thiol drugs).
Radiopacity (X-ray)	Moderately to highly radiopaque (easily seen).	Highly radiopaque (dense, easily seen).	Radiolucent to weakly radiopaque (hard to see).	Radiolucent to weakly radiopaque.
Urine pH Association	Alkaline (pH > 7.0).	Acidic to neutral (pH < 6.5).	Acidic to neutral (pH < 6.5).	Acidic (pH < 6.0).
UTI Association	Almost always associated with urease-producing UTI.	Not typically associated with UTI.	Not typically associated with UTI.	Not typically associated with UTI.
Breed Predisposition	Miniature Schnauzer, Shih Tzu, Cocker Spaniel, females.	Miniature Schnauzer, Yorkie, Poodle, Bichon, males.	Dalmatian, English Bulldog, dogs with liver shunts.	Newfoundland, Mastiff, English Bulldog, Dachshund.
Primary Prevention	Prevent UTIs, maintain pH ~6.5, promote water intake.	Maintain pH 6.5–7.5, high water, low oxalate diet.	Maintain pH 7.0–7.5, low purine diet, water.	Maintain pH 7.5–8.0, low protein diet, high water.

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The signs (stranguria, hematuria, obstruction) and when it is an emergency

Bladder stones cause clinical signs by physically irritating the sensitive lining of the bladder (the urothelium) and proximal urethra. The most common signs observed by owners include:

• Hematuria: Blood in the urine. This occurs because the hard, rough surfaces of the stones rub against the bladder wall, causing micro-trauma and bleeding.
• Dysuria and Stranguria: Painful urination and straining to urinate. The dog may assume the posture to urinate frequently but only pass small drops, or exhibit signs of discomfort during the act.
• Pollakiuria: An increased frequency of urination. The physical presence of the stone irritating the bladder stretch receptors mimics the sensation of a full bladder, causing the dog to feel the urge to urinate constantly.
• Urinary Accidents: A house-trained dog may suddenly start urinating indoors due to the urgency and lack of voluntary control.

The Urethral Obstruction Emergency

While bladder stones are painful and uncomfortable, they are not immediately life-threatening as long as the dog is able to pass urine. However, if a stone (or multiple small stones) leaves the bladder and becomes lodged in the narrow urethra, it can completely block the outflow of urine.

This condition is called urethral obstruction and is a true medical emergency:

• Male Risk: Urethral obstruction is significantly more common in male dogs. The male urethra is longer and narrower than the female urethra, and it must pass through the os penis (a rigid bone in the penis) where the urethra cannot expand. Small stones that would easily pass through a female urethra frequently become wedged behind the os penis in males.
• Pathophysiology: When the urethra is completely blocked, the kidneys continue to produce urine, but it has nowhere to go. Pressure builds up in the bladder, ureters, and kidneys. Within 24 to 48 hours, this backpressure impairs kidney filtration, leading to acute kidney injury (AKI) and uremia (accumulation of toxins in the blood).
• Electrolyte Derangement: The most life-threatening complication of obstruction is hyperkalemia (dangerously high blood potassium). Potassium is normally excreted in the urine. If it accumulates in the blood, it disrupts the electrical conduction of the heart, causing severe bradycardia (slow heart rate), arrhythmias, and eventual cardiac arrest.
• Emergency Triage: If a dog, particularly a male, is seen posturing to urinate repeatedly but producing absolutely no urine, appears painful, vocalizes, or becomes lethargic and starts vomiting, they must be rushed to an emergency veterinary clinic immediately. For a comparison of urethral obstruction protocols and emergency stabilization, read our guide on urinary obstruction in cats.

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How bladder stones are diagnosed: X-ray, ultrasound, urinalysis, and stone analysis

A complete diagnostic workup is required to confirm the presence of uroliths, assess the risk of obstruction, and attempt to predict the mineral composition before initiating therapy.

1. Urinalysis

A fresh urine sample (ideally collected via cystocentesis to avoid contamination) provides vital clues:

• Urine pH: A highly alkaline pH (> 7.5) strongly suggests the presence of urease-producing bacteria, pointing toward a struvite stone. An acidic pH (< 6.5) is more typical for calcium oxalate, urate, or cystine urolithiasis.
• Crystalluria: Identifying the type of crystals under a microscope can help infer the stone type. Double-pyramid "envelope" shapes indicate calcium oxalate dihydrate; "coffin-lid" prisms indicate struvite; "thorn-apple" spheres indicate ammonium urate; and flat hexagons indicate cystine. However, crystal type does not always match the stone type, and crystals can form as a artifact of sample cooling.
• Urine Sediment: The presence of red blood cells confirms hematuria, white blood cells indicate inflammation, and bacteria indicate infection.
• Urine Culture and Sensitivity: Essential for any dog with suspected struvite stones, as managing the underlying bacterial infection is mandatory for stone dissolution.

2. Thoracic and Abdominal Radiographs (X-rays)

X-rays are the primary tool for detecting bladder and urethral stones.

• Radiopacity: Struvite and calcium oxalate contain dense mineral elements (magnesium, calcium, phosphorus) that absorb X-rays, making them highly visible as bright white structures within the bladder outline.
• Radiolucency: Urate and cystine stones are organic compounds that do not absorb X-rays well. They are often radiolucent, meaning they appear as faint shadows or are completely invisible on plain radiographs.
• Urethral View: The radiograph must cover the entire path of the urethra, including the region behind the os penis, to ensure no stones have migrated out of the bladder and caused partial obstruction.

3. Abdominal Ultrasound

Ultrasound is highly sensitive and can detect stones that are invisible on plain X-rays (radiolucent urate or cystine stones, or very small uroliths < 2 mm).

• Stones appear as bright white (hyperechoic) interfaces that cast a distinct dark shadow (acoustic shadowing) beneath them.
• Ultrasound allows the veterinarian to measure the bladder wall thickness (to check for chronic cystitis) and rule out bladder masses, such as transitional cell carcinoma. For more information on differentiating bladder masses from stones, see our clinical guide on canine transitional cell carcinoma.

4. Quantitative Urolith Analysis (The Gold Standard)

The only way to definitively identify the composition of a bladder stone is to submit a retrieved stone to a specialized laboratory, such as the Minnesota Urolith Center. They use optical crystallography and infrared spectroscopy to analyze the layers of the stone, determining the exact percentage of minerals present (e.g., "100% calcium oxalate monohydrate" or "80% struvite and 20% calcium phosphate"). Knowing the exact composition is crucial to design an effective prevention plan.

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The Minnesota Urolith Center data: how common each stone type actually is

To understand the epidemiological landscape of canine urolithiasis, veterinarians rely on data from the Minnesota Urolith Center (MUC) at the University of Minnesota. The MUC has analyzed uroliths from over 1.8 million veterinary patients globally since 1981, providing an unparalleled long-term dataset.

The Historical Shift

Across the 1980s and 1990s, struvite was the dominant canine stone type (averaging roughly 43.5% of submissions over the 1981–2005 period). Over the following decades, a major shift occurred:

• Calcium Oxalate submissions rose steadily and surpassed struvite around 2004, becoming the most common canine urolith type through much of the 2000s and 2010s (calcium oxalate reached roughly 47–49% of submissions in some 2006–2018 datasets).
• More recently the two have traded places again: in the MUC 2023 global data (approximately 63,762 canine submissions), struvite accounted for roughly 41% of uroliths and calcium oxalate for roughly 33%, putting struvite back in the top spot.
• Together, struvite and calcium oxalate still make up roughly three-quarters (about 74%) of all canine bladder stones submitted for analysis.

This shift is attributed to multiple factors, including:

1. Dietary Changes: The widespread use of urinary acidifying diets designed to prevent struvite crystals in dogs may have inadvertently promoted the precipitation of calcium oxalate, which forms more readily in acidic urine.
2. Breed Popularity: The rising popularity of small and toy breeds (which have a genetic predisposition to calcium oxalate) has altered the overall population risk.
3. Improved Infection Control: Better detection and prompt treatment of urinary tract infections in female dogs has reduced the incidence of infection-induced struvite stones.

Breed and Gender Distribution

The MUC data highlights strong demographic correlations that help veterinarians infer stone type before analysis:

• Gender: Struvite stones are far more common in female dogs (roughly 80% of struvite submissions are from females). This is because female dogs have a shorter, wider urethra, making them more susceptible to ascending bacterial UTIs, which trigger struvite formation. Conversely, calcium oxalate stones are more common in male dogs (roughly 60–70% of oxalate submissions are from males).
• Small Breed Predisposition: Small breeds have a significantly higher risk of calcium oxalate stones. The Miniature Schnauzer, Yorkshire Terrier, Shih Tzu, Lhasa Apso, Bichon Frise, and Miniature Poodle are highly over-represented. These breeds tend to produce urine with higher calcium concentrations (hypercalciuria) and lower volumes.
• Urate Specifics: Purine/urate stones are highly associated with the Dalmatian and the English Bulldog. Dalmatians have a genetic mutation in the SLC2A9 gene that impairs uric acid transport in the liver and kidneys, causing them to excrete high levels of uric acid in their urine. In other breeds, urate stones are a classic indicator of a portosystemic shunt (PSS) — a liver vascular anomaly that prevents the conversion of ammonia to urea.

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Medical dissolution protocols for struvite

If a veterinarian suspects a dog has struvite urolithiasis (based on a female dog, alkaline urine, radiopaque stones, and a history of UTI), the first line of treatment is typically medical dissolution rather than surgery. This approach avoids the risks of anesthesia and cystotomy, and it is highly effective.

A successful medical dissolution protocol relies on three concurrent strategies:

1. Feeding a Therapeutic Dissolution Diet

Standard over-the-counter dog foods cannot dissolve bladder stones. The owner must feed a specialized prescription diet (such as Hill's s/d, Royal Canin Urinary S/O, or Purina UR) exclusively. No other food, treats, table scraps, or supplements are allowed, as even small amounts of extra minerals can abort the dissolution process.

These diets are carefully formulated to:

• Reduce Mineral Precursors: Contain restricted levels of protein, phosphorus, and magnesium (the building blocks of magnesium ammonium phosphate).
• Promote Acidic Urine: Target a urine pH of 6.0 to 6.3. Struvite is highly soluble in acidic urine; maintaining a low pH causes the stone to slowly dissolve back into the urine.
• Increase Urine Volume: Contain slightly elevated sodium levels to encourage drinking, which dilutes the urine and helps wash away crystals. Target a urine specific gravity (USG) of less than 1.020.

2. Treating the Underlying Infection

Unlike cats, where struvite stones are often sterile, canine struvite uroliths are almost always caused by a urinary tract infection (UTI). Specifically, they are triggered by urease-producing bacteria, most commonly Staphylococcus pseudintermedius or Proteus mirabilis.

These bacteria produce the enzyme urease, which hydrolyzes urea in the urine into ammonia and carbon dioxide. The ammonia buffering system raises the urine pH (often to > 8.0) and increases the concentration of ammonium and phosphate ions, creating the perfect chemical environment for struvite to precipitate.

• Antibiotic Coverage: The dog must be placed on an appropriate antibiotic (e.g., amoxicillin/clavulanic acid or cefpodoxime) based on a urine culture and susceptibility test.
• Duration: The antibiotic must be administered continuously for the entire duration of the dissolution process. Because bacteria are trapped inside the layers of the stone, as the outer layers dissolve, viable bacteria are released back into the bladder. Stopping antibiotics too early will trigger a recurrence.

3. Monitoring Progress

The veterinarian will monitor dissolution with serial radiographs (or ultrasound) and urinalysis every 3 to 4 weeks:

• Timeframe: Sterile struvite stones can dissolve in as little as 2 to 4 weeks. Infection-induced stones typically take 8 to 12 weeks to dissolve completely.
• Confirmation: The diet and antibiotic must be continued for 2 weeks past the date when the stones are no longer visible on radiographs to ensure any microscopic remnants are completely cleared.

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Physical and surgical removal: when calcium oxalate dominates

If the bladder stone is identified or suspected to be calcium oxalate, medical dissolution is not an option. Calcium oxalate is completely insoluble in canine urine, regardless of pH or diet. The stone will remain in the bladder, acting as a source of pain and infection, unless it is physically removed.

The primary methods for physical removal include:

1. Surgical Cystotomy

This is the traditional, widely available method:

• Procedure: Under general anesthesia, the surgeon makes an incision in the caudal abdomen, exposes the bladder, and makes an incision in the bladder wall (cystotomy) to manually retrieve the stones. The bladder and urethra are then flushed extensively to clear any small fragments before closure.
• Post-op Care: Requires hospitalization, pain management, and monitoring for hematuria. The main risks include anesthetic complications, bladder wall suture failure (uroabdomen), and incomplete stone removal (up to 15–20% of cases leave tiny fragments behind).

2. Voiding Urohydropropulsion (VUH)

A non-surgical flushing technique used for very small stones:

• Mechanism: Under heavy sedation or general anesthesia, the patient's bladder is filled with sterile saline. The dog is held vertically, and the bladder is expressed manually with steady pressure, forcing the small stones to pass out through the urethra.
• Limitations: Only feasible if the stones are smaller than the narrowest diameter of the urethra (typically < 3–5 mm in female dogs, and < 1–2 mm in male dogs). It is highly effective in female dogs due to their wider urethra.

3. Laser Lithotripsy

A minimally invasive technique available at specialty referral centers:

• Mechanism: A specialist passes a rigid or flexible cystoscope through the urethra into the bladder under anesthesia. A laser fiber is introduced through the scope, and laser energy is used to fragment the stones into tiny pieces, which are then flushed out using VUH.
• Benefit: Avoids abdominal surgery, reduces pain, and allows direct visualization to ensure 100% of the stones are removed.

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Preventing recurrence by stone type

Canine urolithiasis has an exceptionally high recurrence rate. Up to 50% of dogs diagnosed with calcium oxalate will form new stones within three years if no preventive measures are taken. Preventing recurrence requires a lifelong commitment from the owner, tailored specifically to the mineral composition of the stone.

The cornerstone of prevention across all stone types is promoting water intake to dilute the urine. Dilute urine keeps mineral ions separated and increases the frequency of urination, physically flushing out crystals before they can aggregate. Owners can achieve this by feeding canned food, adding water to kibble, and utilizing pet water fountains.

1. Preventing Calcium Oxalate

• Diet: Feed a prescription preventive diet (e.g., Royal Canin Urinary S/O, Hill's c/d Multicare) designed to maintain a neutral urine pH (6.5 to 7.5) and minimize calcium and oxalate excretion.
• Avoid High-Oxalate Foods: Do not feed human foods high in oxalates, such as spinach, sweet potatoes, nuts, or chocolate. Avoid excessive vitamin C supplementation (which metabolizes to oxalate) and calcium supplements.
• Medication: If diet alone fails to prevent crystalluria, the veterinarian may prescribe potassium citrate (an oral alkalinizer and calcium chelator) or hydrochlorothiazide (a diuretic that reduces urinary calcium excretion).

2. Preventing Struvite

• Monitor for UTIs: Since canine struvite is almost always infection-induced, the most important preventive step is checking routine urine cultures every 3 to 6 months. If a UTI is detected, treat it promptly with antibiotics.
• Diet: In dogs with chronic, recurrent UTIs that cannot be controlled, a long-term preventive diet that keeps the urine pH slightly acidic (6.3 to 6.8) is indicated.

3. Preventing Urate

• Diet: Feed a low-purine diet (restricted in organ meats, seafood, and yeast) to minimize uric acid production. Hill's u/d is a classic option.
• pH Target: Maintain a highly alkaline urine pH (7.0 to 7.5) to keep uric acid soluble.
• Medication: In Dalmatians with recurrent urate urolithiasis, the drug allopurinol (a xanthine oxidase inhibitor) is used to block the production of uric acid. However, the dose must be carefully monitored; over-dosing can lead to the formation of xanthine stones.

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Frequently Asked Questions

Can bladder stones in dogs be dissolved with food?

Only certain types of bladder stones can be dissolved with food. Struvite stones (magnesium ammonium phosphate) are highly dissolvable using a prescription therapeutic diet that restricts mineral precursors and acidifies the urine. However, calcium oxalate stones (the most common type in dogs) are completely insoluble in urine and cannot be dissolved with food; they must be physically removed through surgery or flushing.

How long does it take to dissolve a struvite stone?

Medical dissolution of a struvite stone typically takes 8 to 12 weeks, depending on the size and number of the stones. Sterile stones can dissolve faster (2 to 4 weeks), but most canine struvite stones are associated with a bacterial infection. The dog must remain on both the dissolution diet and an antibiotic for the entire duration, plus an additional 2 weeks after the stones are no longer visible on X-rays.

Can a dog live with bladder stones, or do they always need surgery?

A dog cannot live comfortably with untreated bladder stones. Even if they do not cause a complete blockage, the stones cause chronic irritation, pain, blood in the urine, and recurrent infections. If the stones are calcium oxalate (which cannot be dissolved), physical removal via surgery, voiding urohydropropulsion, or laser lithotripsy is required. If the stones are struvite, they can be dissolved medically without surgery.

What foods cause bladder stones in dogs?

No single food causes bladder stones in all dogs, but diets high in mineral precursors can increase the risk in predisposed animals. Diets high in calcium, phosphorus, magnesium, or oxalates (such as spinach or sweet potatoes) can promote calcium oxalate or struvite formation. Additionally, diets high in purines (organ meats, red meats, seafood) increase the risk of urate stones, especially in Dalmatians.

What happens if a male dog can't pee because of a stone?

If a male dog is unable to pass urine due to a stone lodging in the urethra, it is a life-threatening emergency. Within 24 to 48 hours, the lack of urination causes acute kidney damage, toxins accumulate in the blood (uremia), and potassium levels rise (hyperkalemia). High potassium disrupts the heart's electrical rhythm, leading to cardiac arrest. Immediate emergency treatment to relieve the blockage (catheterization, retrohydropropulsion, or emergency surgery) is required.

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Sources

1. Minnesota Urolith Center Prevalence & Guidelines: University of Minnesota College of Veterinary Medicine. (2023). Canine Urolith Analysis Overview and Submission Guidance. Minnesota Urolith Center. https://vetmed.umn.edu/urolith-center/urolith-analysis-overview
2. Merck Veterinary Manual - Canine Urolithiasis: Lulich, J. P., & Osborne, C. A. (2020). Urolithiasis in Small Animals. Merck Veterinary Manual. https://www.merckvetmanual.com/urinary-system/urolithiasis-in-small-animals/urolithiasis-in-dogs
3. ACVIM Consensus Guidelines for Urinary Stones: Lulich, J. P., Berent, A. C., Adams, L. G., Westropp, J. L., Bartges, J. W., & Osborne, C. A. (2016). ACVIM Small Animal Consensus Recommendations on the Treatment and Prevention of Canine and Feline Urolithiasis. Journal of Veterinary Internal Medicine, 30(5), 1564–1574. https://pmc.ncbi.nlm.nih.gov/articles/PMC5076618/
4. VIN Veterinary Partner Reference: Brooks, W. (2021). Bladder Stones in Dogs and Cats. Veterinary Partner / VIN. https://veterinarypartner.vin.com/default.aspx?pid=19239&id=9421365
5. Cornell Riney Canine Health Center: Cornell University College of Veterinary Medicine. (2022). Struvite Bladder Stones in Dogs. https://www.vet.cornell.edu/departments-centers-and-institutes/riney-canine-health-center/canine-health-topics/struvite-bladder-stones-dogs
6. VCA Animal Hospitals Reference: Ward, E. (2020). Bladder Stones in Dogs. VCA Hospitals. https://vcahospitals.com/know-your-pet/bladder-stones-in-dogs
7. FDA Docket / Minnesota Urolith Center Data: Minnesota Urolith Center Global Data Report 2023. Referenced in FDA Docket FDA-2023-D-4095-0043. https://downloads.regulations.gov/FDA-2023-D-4095-0043/content.pdf