Urothelium

What is the urothelium?

The urothelium is a highly specialized type of tissue that lines the inside of your urinary tract. It serves as a barrier, preventing urine (pee) from leaking out into your body. It also stretches and contracts as your bladder fills and empties.

More than 90% of bladder cancers start in the urothelium

What is the function of the urothelium?

Your urothelium is a leakproof yet stretchable lining of the inside of your urinary tract.

How does the urothelium work with other organs?

Your urothelium is part of the urinary system, which removes waste and excess water from your blood. Your urinary system is made up of your kidneys, ureters, bladder and urethra. Your kidneys filter your blood and produce urine, which travels through your ureters to your bladder. Urine is stored in your bladder and exits your body through your urethra when you urinate.

Where is the urothelium located?

Your urothelium is the innermost lining of the central part of your kidney (renal pelvis), ureters, bladder and urethra.

What is the urothelium made of?

Your urothelium is a type of epithelial tissue. Epithelial tissues are made of sheets of tightly connected cells. They cover most of the inner and outer surfaces of your body and organs.

What is the structure of the urothelium?

Your urothelium has three layers:

• Apical layer: This is the innermost layer. Cells are shaped like the top of an umbrella and packed together tightly. They’re also covered with a layer of protein plaque that creates a urine-proof barrier.
• Intermediate layer: This middle section is made up of several layers of irregularly shaped cells.
• Basal layer: This outer part is formed from two or three layers of small cube-shaped cells.

Your urothelium stretches in your bladder as it fills with urine. Urothelial cells are stacked and cube-shaped when not stretched. They flatten and spread out when your bladder fills and expands. Due to its shape-altering ability, your urothelium is sometimes called the transitional epithelium.

What types of cancer occur in the urothelium?

Cancer of the urothelium can develop anywhere along the urinary tract. The most common types of cancer involving the urothelium are:

• Bladder cancer: Bladder cancer is the fourth most common cancer in people assigned male at birth (AMAB). It’s less common in people assigned female at birth (AFAB). Most cases of bladder cancer originate in the urothelium (urothelial cancer). Sometimes, urothelial cancer invades the cells surrounding the urothelium (lamina propria), the bladder wall or other parts of the body. Providers detect about half of bladder cancers before cancer spreads beyond the urothelium. Smoking is the main risk factor for bladder cancer.
• Urethral cancer: Cancer can develop in the urothelium of your urethra. In people AFAB, urethral cancer of the urothelium forms near their urethral opening. In people AMAB, it develops as prostatic urothelial cancer, a rare form of prostate cancer. Your prostate gland is located just below your bladder and surrounds your urethra. Prostatic urothelial cancer can develop in the urothelium of your urethra and invade your prostate. This aggressive form of cancer has often spread into surrounding tissues by the time it’s diagnosed.
• Urothelial cancer of the kidneys or ureters: Symptoms include blood in your urine, back pain and frequent or painful urination. People with a history of bladder cancer have a greater chance of developing urothelial cancer in the kidneys or ureters. Smoking is also a risk factor.

What is Lynch syndrome?

People with Lynch syndrome have a genetic mutation that increases their risk of developing certain kinds of cancer, including urothelial cancer. Lynch syndrome runs in families. Healthcare providers can diagnose it using genetic testing.

There is no cure for Lynch syndrome. If you’ve received a Lynch syndrome diagnosis, your provider will recommend routine screening to detect any cancer early on. Catching cancer early offers your best chance for successful treatment. Screening for urothelial cancer involves ultrasound imaging of your urinary tract

Are all bladder tumors cancerous?

Some bladder tumors are noncancerous (benign), though this is rare. These tumors occur due to changes to the bladder cells, but they don’t spread to other parts of the body.

Benign bladder tumors can start in your urothelium or other bladder tissues. Examples of benign bladder tumors that originate in your urothelium are papillomas and inverted papillomas. These tumors may cause blood in your urine. Healthcare providers can remove benign bladder tumors with a cystoscopy.

What is interstitial cystitis?

Interstitial cystitis causes pain, pressure or discomfort in your bladder area. You may experience a continual urge to urinate and may urinate more often. Healthcare providers believe interstitial cystitis is triggered by damage to your urothelium. The damage allows urine to leak into the tissues surrounding your bladder, leading to chronic inflammation and pain.

For most people, interstitial cystitis is a chronic (long-lasting) condition. Noninvasive treatments such as lifestyle changes, oral medications, physical therapy and bladder training can help relieve symptoms. Some people require more invasive procedures or surgery.

What are the symptoms of urothelial conditions?

The most important warning sign of urothelial conditions is hematuria (blood in the urine). Other symptoms include pain in your lower abdomen and painful or frequent urination. Talk to your healthcare provider if you experience any of these symptoms.

How can I prevent urothelial conditions?

You can’t prevent all conditions of your urothelium, but quitting smoking and using tobacco products is the best thing you can do to prevent bladder cancer. You can also see your healthcare provider for:

• Regular physical exams and to discuss any symptoms you may be experiencing.
• Preventive steps you may need to take, especially if you’re at high risk for urothelial conditions.

A note from Cleveland Clinic

If you notice blood in your urine or have pain or pressure in your bladder area, check with your healthcare provider. You’ll need careful evaluation to determine if you have bladder cancer or a noncancerous condition. Treatment for bladder cancer is most effective if cancer is caught early. Your provider will coordinate your care so you can feel better as soon as possible.