Bladder Tumours in Cats & Dogs
Written by Shula Berg BVSc CertAVP(GSAS) GPAdvCert(SASTS) MRCVS
Clinically reviewed by Elizabeth McLennan-Green BVM&S CertAVP(SAM) MRCVS
Table of Contents
Bladder tumours are uncommon tumours in both dogs and cats. In dogs, they are more often seen in older female animals. They can affect any breed, but seem to be more common in West Highland White Terriers, Jack Russel Terriers, Beagles and Scottish Terriers. In cats, bladder tumours are more common in middle-aged to older male animals.
Bladder tumours can be single or multiple, and most commonly develop near to the bladder neck. In both dogs and cats, the majority of bladder tumours are malignant, with the most common type known as transitional cell carcinoma (TCC). Despite this, less than half of animals will have detectable spread at the time of diagnosis.
Bladder tumours cause inflammation in the bladder and have symptoms very similar to cystitis. Common symptoms include:
- Struggling to urinate
- Urinating more often
- Urinating in small volumes
- Blood in the urine
While cystitis will usually get better with a course of medication, in bladder tumours symptoms usually recur once treatment stops. It is important to investigate further in these cases, especially in older animals.
Bladder tumours are usually identified during investigation of non-resolving urinary tract signs. Both resistant infections and bladder stones can cause very similar symptoms, so some of the tests performed will not be specific to bladder tumours.
Initially, a urine sample should be examined for the presence of blood, protein and abnormal cells/crystals. Often a sample is sent to an external lab for culture and sensitivity testing of any bacteria. Pets with bladder tumours can have secondary infections so these tests are still helpful even if a tumour is the ultimate diagnosis.
Ultrasound examination is the most common method of diagnosing bladder tumours. This is performed with the pet awake or lightly sedated, is non-invasive and not painful. Provided there is enough urine in it, the bladder can be thoroughly examined. Often, a large mass is visible. Occasionally, a small mass is present and, though a tumour is suspected, imaging may need to be repeated at a later date to be sure this is not just inflammation of the bladder wall.
Cell Sample Testing
To definitively confirm a tumour, and identify the tumour type, a sample of cells must be obtained. There are several ways this can be performed. The most common method used to diagnose tumours is a fine needle aspirate (FNA), which involves taking a sample of cells directly from the tumour with a needle. This is simple to perform, however, there is a small risk of pulling cancer cells from the bladder into the abdomen. Alternative methods include passing a catheter into the bladder to “suction” cells from the growth, or using an endoscope (camera) to visualise the mass and take a sample. Both of these options will usually require sedation or anaesthesia. Unfortunately, none of these options are guaranteed to obtain enough cells for a diagnosis, so choice of technique is often down to equipment availability and vet preference.
Since up to 50% of bladder tumours will spread elsewhere in the body, known as metastasis, it is often recommended to examine other organs before deciding on definitive treatment. This most commonly includes x-ray of the lungs, and ultrasound examination of the liver and spleen. Your vet will advise you about what is recommended for your pet.
Treatment of bladder tumours can be challenging. Since most develop near the bladder neck, where the ureters implant from the kidneys, it is often not possible to surgically remove the tumour without causing irreparable damage to the urinary tract. Rarely, surgery is appropriate for tumours originating from the body of the bladder.
Medical treatment is often prescribed for bladder tumours. The non-steroidal anti-inflammatory drug (NSAID) Piroxicam is often used to slow down tumour growth, and more readily available NSAIDs such as Meloxicam may have a similar effect. These drugs are very safe and usually well-tolerated. In a very small number of cases, Piroxicam may lead to partial or complete remission. Although chemotherapy has been used in combination for some bladder tumours, there is little evidence to support the benefit of this, and side effects are significantly increased.
The prognosis for bladder tumours is unfortunately considered to be poor, as it is rarely possible to achieve a cure. That said, many patients will have increased comfort on Piroxicam and can remain happy for many months. As with lots of tumours, the more advanced the symptoms are at the time of diagnosis, the more rapidly we will expect the cancer to progress. Ultimately, as the tumour grows, the urethra (out-flow of the bladder) will become blocked and the pet will no longer be able to pass urine. At this point, treatment will not be effective and it is likely your pet will need to be put to sleep. Your vet will be able to discuss the likely progression of symptoms and what to expect in more detail.
Please note that the content made available on this webpage is for general information purposes only. Whilst we try to ensure that at the time of writing all material is up to date and reflects industry standards, we make no representation, warranties or guarantees that the information made available is up to date, accurate or complete. Any reliance placed by yourselves is done so at your own risk.
Page last reviewed: 16th January 2024
Next review due: 16th January 2026