CONDITION

Bladder Polyps

Bladder polyps are growths that project from the inner lining of the bladder into the space where urine is stored. They develop when the bladder's lining tissue thickens and forms raised structures, often in response to long-standing irritation or inflammation. In dogs, this pattern is sometimes called polypoid cystitis, and whilst confirmed polypoid cystitis is a benign inflammatory condition, polyp-like masses seen on imaging or during a cystoscopy cannot be assumed benign without a tissue sample, as some bladder cancers can appear visually similar. Owners most often encounter bladder polyps through blood in the urine—sometimes visible as a pink or red tinge, sometimes detected only during routine testing. Urination may become more frequent, and some animals strain or appear uncomfortable when passing urine. These signs overlap with other bladder conditions, including infection, stones, and tumours, which is why further investigation is typically needed to understand what is present. This page explores the signs that may prompt investigation, what may be happening in the bladder tissue, the ways these growths are identified and sampled, and the range of approaches used once a diagnosis is confirmed.

Why this matters now

Bladder polyps tend to develop in middle-aged to older dogs, with a median age of around eight and a half years in the largest documented case series. No consistent breed predisposition has been identified, and dogs of a wide range of breeds, including a substantial proportion of mixed-breed dogs, have been affected. Female dogs are somewhat more commonly affected than males, and the condition often emerges in animals with a history of recurrent bladder inflammation, urinary tract infection, or the presence of bladder stones.

The progression of bladder polyps varies considerably between individuals. In many cases, polyps remain stable for months or years, causing intermittent signs that wax and wane with episodes of bladder irritation or infection. Some growths regress partially or completely when the underlying inflammation is addressed, whilst others persist despite treatment of contributing factors. Occasionally, polyps increase in size or number over time, and in rare instances long-standing polypoid tissue may undergo change that raises concern for malignancy, which is why tissue sampling is often pursued when these structures are identified.

Signals & patterns

Early signals

Blood in the urine

Urine may appear pink, red, or tea-coloured, or blood may be detected only during laboratory testing of a sample that looks clear to the eye. This occurs because polyps can bleed intermittently as urine flows past them or when the bladder wall contracts during urination.

More frequent trips outside

The dog may ask to go out more often than usual, passing small amounts of urine each time. This pattern arises because polyps, and the inflammation around them, can make the bladder feel fuller than it is, prompting the urge to urinate before much urine has accumulated.

Straining or discomfort whilst urinating

The dog may take longer to urinate, adopt an uncomfortable posture, or vocalise softly during the act. Polyps can partially obstruct the flow of urine or create localised discomfort as the bladder wall contracts around them.

Licking at the genital area

Increased attention to the area may follow irritation or discomfort in the urethra or bladder. Some dogs will lick persistently after urinating, particularly if blood or inflammation is present.

Later signals

Persistent or worsening haematuria

Blood in the urine becomes more consistent or more visibly pronounced over time, often no longer responding to treatments that previously reduced the sign. This may indicate enlargement of existing polyps or the development of additional growths.

Difficulty emptying the bladder

The dog may strain for prolonged periods with little urine passed, or begin dribbling urine involuntarily. Larger polyps, or those positioned near the bladder neck, can interfere with normal outflow, and incomplete emptying increases the risk of secondary infection.

Recurrent urinary tract infections

Infections that resolve with treatment but return weeks or months later can occur when polyps harbour bacteria in folds of inflamed tissue or when incomplete bladder emptying allows stagnant urine to persist. This creates a cycle of infection and further irritation.

Click to read about the biological mechanisms

How this is usually investigated

Investigation typically begins with a detailed history—particularly the pattern of urinary signs, any previous bladder infections or stones, and response to earlier treatment—followed by a physical examination to assess the bladder and surrounding structures. Initial testing focuses on urine analysis and imaging to identify what is present within the bladder. When a mass or polyp-like structure is seen, tissue sampling is often pursued to distinguish benign inflammatory polyps from other growths that may require different management.

Urinalysis with sediment

Purpose: Examination of the urine identifies blood, inflammatory cells, crystals, and bacteria, providing clues to the nature and extent of bladder irritation. The presence of abnormal cells in the sediment can sometimes raise concern for malignancy, though their absence does not exclude it.
Considerations: Urine samples collected at home or by free catch may be contaminated, and inflammatory changes can overlap with infection or other bladder conditions. Sediment findings inform the next steps but rarely confirm a diagnosis on their own.

Bacterial culture and sensitivity

Purpose: Culture identifies whether bacteria are present in the bladder and determines which antibiotics are likely to be effective. Many animals with bladder polyps have concurrent or recurrent urinary tract infections that perpetuate inflammation.
Considerations: A negative culture does not exclude all forms of bladder irritation, and some infections are intermittent. The sample collection method—ideally cystocentesis, a needle draw through the body wall—affects the reliability of the result.

Abdominal ultrasound

Purpose: Ultrasound imaging allows visualisation of the bladder wall and any masses or thickened areas within it. Polyps often appear as irregular, raised projections extending into the bladder lumen, and ultrasound can also identify stones or other concurrent abnormalities.
Considerations: Ultrasound can detect the presence of a growth but cannot reliably distinguish benign polyps from early-stage tumours based on appearance alone. The size and location of the polyp may limit visibility, particularly if the bladder is not well filled.

Cystoscopy with biopsy

Purpose: A cystoscope—a narrow camera inserted through the urethra—provides direct visualisation of the bladder lining and allows guided sampling of suspicious tissue. This is often the most definitive way to assess polyp-like structures and obtain samples for histopathology.
Considerations: Cystoscopy requires general anaesthesia and specialised equipment, which may not be available at all practices. In male dogs with a narrow urethra, the scope may not reach the bladder, and bleeding after biopsy is common though usually resolves without intervention.

Histopathology

Purpose: Microscopic examination of tissue taken from the bladder confirms whether the growth is benign polypoid cystitis, another inflammatory process, or a malignant tumour. This distinction shapes all subsequent management decisions.
Considerations: Tissue samples must be of sufficient size and quality for accurate interpretation, and results typically take several days to return. Sampling error can occur if the biopsy does not capture the full depth of the lesion or misses areas of early malignant change.

Options & trade-offs

Management is usually a combination of approaches tailored to the individual animal, the nature of the polyps, and any underlying factors that may be perpetuating inflammation. Some animals respond well to medical management alone, whilst others benefit from removal of the growths, and many require ongoing attention to bladder health over time. Different owners and animals find different combinations workable, depending on tolerance for procedures, the pattern of signs, and how the polyps behave over months to years.

Medical management of inflammation and infection

This involves treating any identified urinary tract infection with antibiotics selected by culture and sensitivity, addressing bladder stones or crystals if present, and sometimes using anti-inflammatory medications to reduce irritation of the bladder lining. In cases where polyps appear to be driven by chronic inflammation, this approach can lead to partial or complete regression of the growths over weeks to months. Some animals are maintained on long-term strategies to prevent recurrent infection or crystal formation.

Trade-offs: Medical management requires patience and often repeated urine testing to monitor response. Not all polyps regress with treatment of underlying causes, and some persist despite resolution of infection or inflammation. This approach is less invasive than surgery but may involve prolonged medication and does not provide tissue for definitive diagnosis if sampling has not already occurred.

Surgical removal via cystotomy

A cystotomy is an open surgical procedure in which the bladder is accessed through an incision in the abdomen, allowing the surgeon to excise polyps and inspect the bladder lining directly. This provides tissue for histopathology and can resolve signs if the polyps are the primary source of bleeding or irritation. The bladder wall is then sutured closed, and recovery typically involves a period of restricted activity and monitoring for post-operative infection.

Trade-offs: Cystotomy is an invasive procedure requiring general anaesthesia and carries the usual surgical risks, including bleeding, infection, and complications related to healing of the bladder wall. It may not be suitable for animals with multiple small polyps or those in locations difficult to access, and recurrence can occur if the underlying inflammatory process is not addressed.

Laser ablation via cystoscopy

In this approach, a laser delivered through a cystoscope is used to vaporise or excise polyps whilst visualising the bladder lining in real time. This is less invasive than open surgery, often involves a shorter recovery period, and allows treatment and sampling in a single procedure. It is particularly useful for polyps that are pedunculated—attached by a narrow stalk—or located in areas difficult to reach surgically.

Trade-offs: Laser ablation requires specialised equipment and expertise, which may only be available at referral centres. The technique is less effective for large, broad-based polyps or for those involving extensive areas of the bladder wall. Tissue retrieved by laser may be fragmented or heat-damaged, which can complicate histopathological interpretation, and recurrence remains possible if inflammation persists.

Monitoring without active intervention

In cases where polyps are small, causing minimal signs, and appear stable on repeat imaging, some owners and vets choose to monitor the situation with periodic urine testing and ultrasound rather than pursuing immediate removal. This approach is often considered when the animal is otherwise well, when the risks of anaesthesia or surgery are deemed significant, or when tissue sampling has already confirmed benign disease.

Trade-offs: Monitoring avoids the risks and costs of intervention but requires vigilance for changes in the size or behaviour of the polyps and for any worsening of urinary signs. There is a small possibility that long-standing polypoid tissue may undergo malignant transformation over time, and delaying removal means that signs such as bleeding or discomfort may persist or recur intermittently.

Common misconceptions

Misconception:

"A bladder polyp is always benign and does not require biopsy or removal."

Reality:

Whilst confirmed polypoid cystitis is a benign inflammatory condition, polyp-like masses seen on ultrasound or cystoscopy cannot be assumed benign without tissue sampling, as some bladder cancers can appear visually similar. Biopsy is often pursued to distinguish these possibilities and inform management decisions.

Misconception:

"Once a bladder polyp is removed, it will not come back."

Reality:

Polyps can recur if the underlying source of bladder irritation—such as recurrent infection, crystals, or stones—is not addressed. Even with successful treatment of these factors, some animals develop new polyps over time, which is why periodic monitoring is often part of long-term management.

Misconception:

"Blood in the urine always means the polyp is getting worse."

Reality:

Haematuria in animals with bladder polyps tends to be intermittent and can fluctuate with episodes of bladder irritation, minor trauma to the fragile tissue, or concurrent infection. The presence of blood does not necessarily indicate progression of the polyp itself, though any change in the pattern or severity of bleeding warrants further assessment.

Related conditions

Feline Idiopathic Cystitis

Feline idiopathic cystitis can produce signs that overlap closely with those of bladder polyps—blood in the urine, frequent urination, and straining—making imaging or cystoscopy necessary to distinguish inflammatory bladder wall changes from discrete polypoid masses.

Anal Sac Adenocarcinoma

Anal sac adenocarcinoma can cause elevated blood calcium levels, which in turn may predispose to the formation of bladder stones; stones and chronic irritation are recognised contributors to polypoid change in the bladder lining, creating an indirect link between the two conditions.

Foreign Body Ingestion

Foreign body ingestion involving materials that reach the bladder—such as migrating plant awns or fragments that pass through the urethra—can cause chronic irritation and inflammation of the bladder lining, which may contribute to the development of polypoid cystitis over time.

Cholangiocarcinoma

Whilst polyps in the bladder are often benign inflammatory growths, the visual appearance of a polypoid mass on imaging cannot reliably distinguish benign tissue from malignancy such as transitional cell carcinoma; cholangiocarcinoma represents a similar diagnostic challenge in the bile ducts, where irregular masses require tissue sampling to confirm their nature.

For animals with bladder polyps, attention often extends to the pattern of urinary signs over time, any recurring infections or crystal formation, and the balance between active treatment and longer-term monitoring. Understanding the broader context of bladder health—including the role of hydration, diet, and early recognition of changes in urination—can inform conversations with the practice. These threads often connect to questions about imaging findings, tissue sampling, and what different management paths might involve in practical terms.

Last reviewed: 13 September 2026 · Dr Alastair Greenway MRCVS