Polypoid cystitis

By Elena Pastukhova BSc and Trevor Flood MD FRCPC
June 11, 2025

Polypoid cystitis is a non-cancerous condition caused by long-term (chronic) irritation or inflammation of the bladder’s inner lining. The term polypoid refers to abnormal growths that protrude or stick out from the tissue surface, while cystitis describes inflammation within the bladder. Polypoid cystitis is reversible and typically improves once the source of irritation is removed.

What causes polypoid cystitis?

Polypoid cystitis most often develops due to irritation caused by urinary catheters. A catheter is a tube placed into the bladder to help drain urine, usually for medical reasons. The risk and severity of polypoid cystitis increase with longer periods of catheter use.

Other factors that can injure or irritate the bladder lining and lead to polypoid cystitis include:

• Vesical fistulas (abnormal connections between the bladder and nearby organs).

• Kidney or bladder stones.

• Radiation therapy to the pelvic area (often used for cancer treatment).

If treatment is necessary, it generally involves removing or correcting the source of irritation.

What are the symptoms of polypoid cystitis?

Common symptoms of polypoid cystitis include:

• Frequent need to urinate.

• Pain or discomfort during urination.

• Blood visible in urine (hematuria).

• Abdominal or pelvic pain.

• Difficulty completely emptying the bladder.

Symptoms can vary depending on the severity of inflammation and the underlying cause.

How is polypoid cystitis found and diagnosed?

Your doctor may suspect polypoid cystitis if you have symptoms such as blood in the urine, pain during urination, or difficulty emptying your bladder, especially if you have a history of bladder irritation or injury, such as prolonged catheter use or pelvic radiation therapy.

To diagnose polypoid cystitis, your doctor may use imaging tests, such as an ultrasound or CT scan, to examine your bladder. On these scans, polypoid cystitis can sometimes look like a mass, mimicking bladder cancer.

Due to this similarity, your doctor might recommend a procedure called a cystoscopy. During cystoscopy, a narrow tube with a small camera is inserted into your bladder, allowing your doctor to directly view the bladder lining. During this procedure, the doctor can remove a small sample of bladder tissue, known as a biopsy.

A pathologist will then carefully study the biopsy sample under a microscope to confirm the diagnosis and rule out conditions like bladder cancer.

What does polypoid cystitis look like under the microscope?

When pathologists examine bladder tissue from a patient with polypoid cystitis, they observe changes in both the urothelium (the surface lining) and the stroma (the underlying tissue).

Changes in the urothelium

The urothelium (the inner lining of the bladder) may look either normal or slightly crowded due to an increased number of cells. Pathologists refer to this increase in cell numbers as hyperplasia. Sometimes, these cells grow into elongated, finger-like structures called fronds. These fronds can have either a broad or narrow base and might appear as single growths or as multiple branching projections.

Changes in the stroma

Beneath the urothelium is supportive tissue known as the stroma, which often shows several distinctive changes. In polypoid cystitis, specialized immune cells are frequently seen in the stroma, reflecting ongoing inflammation. Other common signs of chronic inflammation, such as tissue edema (swelling) and fibrosis (scarring), are also typically present.

Additionally, the stroma may exhibit a non-cancerous change known as metaplasia. Metaplasia is a term used by pathologists to describe cells that have changed from their normal type into another specialized cell type, often in response to chronic irritation.

Ruling out bladder cancer (papillary urothelial carcinoma)

An essential part of your pathologist’s examination involves carefully distinguishing polypoid cystitis from bladder cancer, especially a type called papillary urothelial carcinoma, which can look similar.

Key differences your pathologist looks for include:

• Nuclear appearance: Cells in polypoid cystitis usually have only one nucleus per cell, and these nuclei tend to be similar in size and shape. In bladder cancer, cells often have more than one nucleus (multinucleated) and exhibit significant variation in size and shape. These cells are described as pleomorphic.

• Cell division (mitotic figures): While some dividing cells (mitotic figures) might be seen in polypoid cystitis, cancerous cells divide much more frequently. A high number of dividing cells is strongly suggestive of cancer rather than polypoid cystitis.

These careful examinations help pathologists accurately differentiate between polypoid cystitis and bladder cancer.

How is polypoid cystitis treated?

Treatment for polypoid cystitis focuses primarily on removing or addressing the cause of irritation. If a urinary catheter is the cause, your doctor may remove or replace it. If bladder stones, radiation, or other underlying conditions are causing irritation, addressing these factors will often resolve the inflammation. Once the source of irritation is removed, the bladder usually heals over time.

Can polypoid cystitis become cancerous?

Polypoid cystitis itself is not cancerous and does not develop into cancer. However, due to its appearance, it can mimic bladder cancer in imaging studies and during cystoscopy. For this reason, accurate diagnosis by biopsy is essential.

Follow-up care

Your doctor may recommend regular follow-up appointments, especially if symptoms persist or if there’s an ongoing risk of bladder irritation. These appointments may include repeat imaging or cystoscopy to monitor the bladder lining and ensure healing.

Questions to ask your doctor

• What is causing my polypoid cystitis?

• Do I need treatment, or will my symptoms improve on their own?

• Should I avoid specific activities or substances that might further irritate my bladder?

• What follow-up tests or appointments will I need?

• Could my symptoms come back after treatment?

• How can I prevent polypoid cystitis from occurring again?

• How can I differentiate between symptoms of polypoid cystitis and symptoms that might suggest bladder cancer?