Bladder Cancer vs Bladder Stones on Dog Ultrasound

Name: Bladder Cancer vs Bladder Stones on Dog Ultrasound
Creator: Dr. Zubair Khalid

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-10-03

Bladder cancer in dogs ultrasound can often be told apart from bladder stones, but not always. Stones usually look like bright, rounded shapes that cast a strong acoustic shadow, while tumors tend to look like irregular soft tissue masses attached to the bladder wall. Some dogs have both at the same time, and some stones or tumors do not follow the textbook picture, so ultrasound findings usually need a second test to confirm the diagnosis.

This article is educational and is not a substitute for veterinary diagnosis or treatment.

Quick Answer

Ultrasound is very good at finding bladder stones and at spotting a mass, but it cannot always say for certain whether a mass is cancer.
Stones typically appear as bright (hyperechoic) structures with a dark shadow behind them. Tumors usually appear as tissue-density masses growing from the bladder wall.
A mass that is broad-based, irregular, or located at the bladder neck (trigone) raises more concern for cancer, especially urothelial carcinoma, the most common malignant bladder tumor in dogs [1][2].
The usual next step after a suspicious ultrasound is sampling the mass, either by fine-needle aspirate or by biopsy, plus staging tests to check for spread.
Stones can often be managed with diet, antibiotics, or surgery, while bladder cancer is usually managed with a combination of drugs, radiation, or surgery [3][4].

What Ultrasound Can and Cannot Tell Apart

Ultrasound is one of the most useful first tests for a dog with bloody urine, straining to urinate, or frequent small urinations. It is painless, does not use radiation, and lets your veterinarian see the inside of the bladder in real time.

What stones look like on ultrasound

Bladder stones in dogs ultrasound typically appear as bright, rounded or faceted shapes sitting in the bladder. Struvite stones, one of the most common types in dogs, often have a smooth, round, or faceted appearance [5]. Because mineral blocks sound waves, most stones cast a dark "acoustic shadow" underneath them. That shadow is a strong clue that the structure is mineralized instead of soft tissue.

Stones can be single or multiple. They can sit loose in the bladder, or they can be stuck to the wall. Struvite stones form most often because of a urinary tract infection with urease-producing bacteria, which makes the urine more alkaline and concentrated so crystals stick together into a stone [3].

What a bladder mass looks like on ultrasound

An ultrasound bladder mass in a dog usually looks like a soft tissue structure growing from the bladder wall. It may be smooth or irregular, broad-based or stalk-like, and it may or may not move when the dog is repositioned. A tumor does not cast the dense shadow that a stone does, though it can create a softer shadow if it is large.

Urothelial carcinoma (also called transitional cell carcinoma) is the most common malignant tumor of the canine bladder and urethra [1]. It tends to be slow growing and spreads late, but the metastatic rate is still high, with about 50% of cases developing metastases, most often to nearby lymph nodes and the lungs [6]. Because of that, finding a mass on ultrasound is only part of the picture. Your veterinarian will also want to check the rest of the body for spread.

Where ultrasound gets tricky

Ultrasound cannot always separate the two. A stone stuck to the bladder wall can look like a mass. A tumor can have mineralized areas that cast a shadow and mimic a stone. A blood clot or a polyp can also look like a mass. Some dogs have both stones and a tumor at the same time, which is why a case report described a dog with a suspected trigonal tumor plus extensive stones throughout the urinary tract [7].

Cystoscopy (using a small camera to look inside the bladder) can help your veterinarian see the surface of a mass and take a biopsy at the same time. In two dogs with solitary bladder masses, cystoscopy was used during surgery to help plan removal of the tumor with clean margins [8].

For a deeper look at how ultrasound is used across the whole urinary tract, see Ultrasound of the Canine and Feline Urinary Tract: Kidneys, Ureters, and Bladder. If your veterinarian is also considering X-rays, Radiographic and Ultrasonographic Diagnosis of Urolithiasis in Dogs and Cats explains how the two imaging methods compare.

Why Your Veterinarian Recommends Ultrasound

Ultrasound is usually recommended when your dog has signs of lower urinary tract disease that do not clear up with a short course of treatment, or when a urinalysis shows blood, crystals, or infection. Signs include:

Bloody urine
Straining to urinate
Urinating often in small amounts
Accidents in the house
Licking at the genital area

Your veterinarian may also be able to feel large stones during a physical exam by palpating the abdomen [3]. Ultrasound then confirms what is there and where it sits.

Ultrasound also helps your veterinarian plan treatment. A stone in the bladder might be dissolved with diet or removed with a procedure called voiding urohydropropulsion, where the bladder is filled with fluid and the stone is flushed out while the dog urinates. Dogs with a history of calcium oxalate or urate stones may be monitored with imaging every few months so stones can be caught while they are still small enough for this approach [5].

A mass, on the other hand, changes the plan completely. It usually means sampling, staging, and a discussion about cancer treatment.

How to Prepare Your Dog for the Ultrasound

Most bladder ultrasounds need little preparation. In many cases, your dog can eat normally. Some veterinarians ask you to withhold food for a few hours if other organs will be scanned at the same time.

A full bladder gives the best pictures. If your dog urinates right before the appointment, the bladder walls may look thick and folded, which can be mistaken for disease. Ask the front desk whether you should let your dog urinate before coming in.

If sedation is planned, follow the fasting instructions exactly. Tell your veterinarian about all medications, supplements, and any history of kidney or liver disease. Some dogs with liver problems, such as primary portal vein hypoplasia, are more likely to form certain stones, so that history matters [9].

What Happens During the Ultrasound

Your dog lies on a padded table, usually on their side or back. A small area of fur over the belly is clipped, and gel is applied. A handheld probe is moved over the skin. Most dogs tolerate this well, and many relax or even fall asleep.

The exam usually takes 15 to 30 minutes. Your veterinarian or a veterinary radiologist watches the screen in real time and captures images. They will look at the bladder wall, the urine inside, the urethra, the kidneys, and the ureters.

If a mass is seen, your veterinarian may measure it, note its location, and check whether it involves the trigone (the area where the ureters enter the bladder). Tumors in that area are harder to remove surgically and more likely to cause urinary blockage [1][7].

In some cases, your veterinarian may recommend a fine-needle aspirate or a traumatic catheterization sample during the same visit. These samples go to a lab for analysis. A biopsy gives a more definitive answer than an aspirate, but it usually requires sedation or anesthesia.

Recovery and Home Care

Ultrasound itself needs no recovery time. Your dog can go home right after the appointment and resume normal activity. If sedation, a biopsy, or a procedure was done, the timeline below gives a general guide.

Time after procedure	What to expect	What to do
First few hours	Sleepy if sedated, may have mild groin discomfort from the probe	Offer water, let them rest in a quiet space
12 to 24 hours	Back to normal energy in most dogs	Normal meals unless told otherwise
1 to 3 days	Mild blood in urine is possible after a biopsy or catheter sample	Watch for clots, straining, or not urinating
3 to 7 days	Results from lab samples usually come back	Call if you have not heard from the clinic
1 to 2 weeks	Recheck if a procedure was done	Follow all medication instructions exactly

If your dog had a urethral stent placed for a blockage, urine flow often returns quickly, and kidney values can improve within a few days [7]. Your veterinarian will set the follow-up schedule based on your dog's case.

Possible Complications and Warning Signs

Ultrasound is very safe. The main risks come from procedures done at the same time, such as sedation, biopsy, or stent placement.

Call your veterinarian the same day if you see:

Your dog straining to urinate with little or no urine coming out
Crying or pacing while trying to urinate
Blood clots in the urine
Vomiting or refusing to eat after sedation
A swollen or painful belly

Go to an emergency clinic right away if your dog cannot urinate at all. A blocked urethra is a life-threatening emergency, especially in male dogs. Tumors near the trigone and stones lodged in the urethra can both cause this [1][7].

Questions to Ask Your Veterinarian

Bring a written list. These questions help you understand what the ultrasound found and what comes next.

Did you see a stone, a mass, or both?
If you saw a mass, where is it, and does it involve the trigone?
Do you recommend a biopsy, and how will it be done?
What staging tests do you recommend to check for spread?
What are the treatment options, and what is the goal of each one?
How often should we repeat imaging?
What signs mean I should call you right away?

If your dog has stones, ask whether medical dissolution is an option. Struvite stones often respond to antibiotics and a therapeutic diet, though surgery is sometimes needed [3]. If your dog has a tumor, ask about the full range of options. Chemotherapy is generally considered the primary management for urothelial carcinoma, and surgery has been used in selected cases [1]. Radiation therapy has also been used, and in one study, a hypofractionated protocol was well tolerated with mostly low-grade side effects [4].

For more on stone management, see Canine Urolithiasis: Diagnosis and Medical Management and Canine Urolithiasis: Medical Dissolution and Prevention.

Limitations and When to Contact a Veterinarian

Ultrasound is a picture, not a diagnosis. It cannot tell you with certainty whether a mass is benign or malignant. Only a tissue sample sent to a lab can do that. Even the most experienced veterinarian can be surprised by what a biopsy shows.

Contact your veterinarian the same day if your dog has blood in the urine that is getting worse, is straining to urinate, or seems painful.

Go to an emergency clinic now if your dog cannot pass urine, is vomiting repeatedly, or is collapsed or very weak.

Schedule a routine visit if your dog has had a suspicious ultrasound finding and you have not yet discussed the results, or if your dog has a history of stones and is due for a recheck.

Every dog is different. Your veterinarian needs to examine your dog and review the full history to make the right call for your pet.

Frequently Asked Questions

Can an ultrasound tell if a bladder mass is cancer?

No, ultrasound alone cannot confirm cancer. It can show the size, shape, and location of a mass, and it can raise or lower suspicion, but a biopsy is needed to confirm the diagnosis. Your veterinarian may also recommend staging tests to see whether the tumor has spread.

Do bladder stones always show up on ultrasound?

Most bladder stones are visible on ultrasound because they are mineralized and cast a shadow. Very small stones, stones stuck to the wall, or stones made of certain materials can be harder to see. X-rays are sometimes used alongside ultrasound to get a fuller picture.

Can a dog have bladder stones and bladder cancer at the same time?

Yes, this does happen. One case report described a dog with a suspected trigonal tumor plus extensive stones throughout the urinary tract [7]. When both are present, treating the stones alone will not fix the problem, and treating the tumor alone may not restore comfortable urination.

What is the next step after a suspicious ultrasound?

The next step is usually sampling the mass. This can be a fine-needle aspirate, a catheter-based sample, or a biopsy. Your veterinarian will also likely recommend blood work, chest X-rays, and possibly an abdominal ultrasound of other organs to check for spread.

Is bladder cancer in dogs painful?

It can be. Many dogs with bladder cancer have bloody urine, straining, and frequent urination, which are signs of discomfort [2]. Pain control is part of good care, so tell your veterinarian if your dog seems uncomfortable. Treatment often improves these signs even when a cure is not possible.

References

Case Report: Surgical excision of urethral transitional cell carcinoma by total urethrectomy combined with partial cystectomy and vesicovaginal urinary diversion in two female dogs. Frontiers in veterinary science, 2026.
Silent Threats: A Narrative Review of Urinary Bladder Cancer in Dogs and Cats-Epidemiology and Risk Factors. Animals : an open access journal from MDPI, 2026.
Struvite bladder stones in dogs. Cornell University College of Veterinary Medicine.
Incorporating Hypofractionated Radiotherapy Improves Management of Canine Urothelial Carcinoma: A Retrospective Study. Veterinary radiology & ultrasound : the official journal of the American College of Veterinary Radiology and the International Veterinary Radiology Association, 2026.
Urolithiasis in Dogs - Urinary System. Merck Veterinary Manual.
A case of canine urothelial carcinoma of the urinary bladder with skull and skeletal metastases. Australian veterinary journal, 2026.
Case Report of Urethral Stenting in a Dog with Multifactorial Lower Urinary Tract Obstruction Associated with Suspected Transitional Cell Carcinoma and Severe Cystolithiasis. Veterinary sciences, 2026.
Laparoscopic stapled partial cystectomy with intraoperative cystourethroscopy for urothelial carcinoma in two dogs. Veterinary surgery : VS, 2026.
Urolithiasis and crystalluria in dogs with primary portal vein hypoplasia: a retrospective study (2010-2023). The Journal of small animal practice, 2026.