Cystitis signs and symptoms often include:

• A strong, persistent urge to urinate
• A burning sensation when urinating
• Passing frequent, small amounts of urine
• Blood in the urine (hematuria)
• Passing cloudy or strong-smelling urine
• Pelvic discomfort
• A feeling of pressure in the lower abdomen
• Low-grade fever

In young children, new episodes of accidental daytime wetting also may be a sign of a urinary tract infection (UTI). Nighttime bed-wetting on its own isn't likely to be associated with a UTI.

Your urinary system includes your kidneys, ureters, bladder and urethra. All play a role in removing waste from your body. Your kidneys — a pair of bean-shaped organs located toward the back of your upper abdomen — filter waste from your blood and regulate the concentrations of many substances. Tubes called ureters carry urine from your kidneys to the bladder, where it's stored until it exits your body through the urethra.

Bacterial cystitis

UTIs typically occur when bacteria outside the body enter the urinary tract through the urethra and begin to multiply. Most cases of cystitis are caused by a type of Escherichia coli (E. coli) bacteria.

Bacterial bladder infections may occur in women as a result of sexual intercourse. But even sexually inactive girls and women are susceptible to lower urinary tract infections because the female genital area often harbors bacteria that can cause cystitis.

Noninfectious cystitis

Although bacterial infections are the most common cause of cystitis, a number of noninfectious factors also may cause the bladder to become inflamed. Some examples include:

• Interstitial cystitis. The cause of this chronic bladder inflammation, also called painful bladder syndrome, is unclear. Most cases are diagnosed in women. The condition can be difficult to diagnose and treat.
• Drug-induced cystitis. Certain medications, particularly the chemotherapy drugs cyclophosphamide and ifosfamide, can cause inflammation of your bladder as the broken-down components of the drugs exit your body.
• Radiation cystitis. Radiation treatment of the pelvic area can cause inflammatory changes in bladder tissue.
• Foreign-body cystitis. Long-term use of a catheter can predispose you to bacterial infections and to tissue damage, both of which can cause inflammation.
• Chemical cystitis. Some people may be hypersensitive to chemicals contained in certain products, such as bubble bath, feminine hygiene sprays or spermicidal jellies, and may develop an allergic-type reaction within the bladder, causing inflammation.
• Cystitis associated with other conditions. Cystitis may sometimes occur as a complication of other disorders, such as diabetes, kidney stones, an enlarged prostate or spinal cord injuries.

Some people are more likely than others to develop bladder infections or recurrent urinary tract infections. Women are one such group. A key reason is physical anatomy. Women have a shorter urethra, which cuts down on the distance bacteria must travel to reach the bladder.

Women at greatest risk of UTIs include those who:

• Are sexually active. Sexual intercourse can result in bacteria being pushed into the urethra.
• Use certain types of birth control. Women who use diaphragms are at increased risk of a UTI. Diaphragms that contain spermicidal agents further increase your risk.
• Are pregnant. Hormonal changes during pregnancy may increase the risk of a bladder infection.
• Have experienced menopause. Altered hormone levels in postmenopausal women are often associated with UTIs.

Other risk factors in both men and women include:

• Interference with the flow of urine. This can occur in conditions such as a stone in the bladder or, in men, an enlarged prostate.
• Changes in the immune system. This can happen with certain conditions, such as diabetes, HIV infection and cancer treatment. A depressed immune system increases the risk of bacterial and, in some cases, viral bladder infections.
• Prolonged use of bladder catheters. These tubes may be needed in people with chronic illnesses or in older adults. Prolonged use can result in increased vulnerability to bacterial infections as well as bladder tissue damage.

In men without any predisposing health issues, cystitis is rare.

When treated promptly and properly, bladder infections rarely lead to complications. But left untreated, they can become something more serious. Complications may include:

• Kidney infection. An untreated bladder infection can lead to kidney infection, also called pyelonephritis (pie-uh-low-nuh-FRY-tis). Kidney infections may permanently damage your kidneys.

Young children and older adults are at the greatest risk of kidney damage from bladder infections because their symptoms are often overlooked or mistaken for other conditions.

• Blood in the urine. With cystitis, you may have blood cells in your urine that can be seen only with a microscope (microscopic hematuria) and that usually resolves with treatment. If blood cells remain after treatment, your doctor may recommend a specialist to determine the cause.

Blood in the urine that you can see (gross hematuria) is rare with typical, bacterial cystitis, but this sign is more common with chemotherapy- or radiation-induced cystitis.