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Bladder Infection (Cystitis)

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What is the bladder?

The bladder is a hollow muscular organ that is located in the pelvis. The bladder has two functions: one is to store urine and the other is to release/expel urine. Urine drains from the kidneys (one on each side of the body), down the ureters (one on each side of the body), and into the bladder. The urine is stored in the bladder where it remains until urination. When it is time to urinate, the bladder muscle contracts and the outlet of the bladder and sphincter muscles relax to allow urine to pass through the urethra to leave the body. The bladder and urethra are part of the lower urinary tract, whereas the kidneys and ureters are part of the upper urinary tract.

What is a bladder infection?

Cystitis is inflammation of the bladder. Most cystitis is from bacterial infections involving the bladder and less commonly may be the result of yeast infections, viral infections, chemical irritants of the bladder, or for unknown reasons (interstitial cystitis). Bladder infection (infectious cystitis) is a type of urinary tract infection (UTI). This review will specifically address infectious cystitis.

The urine in the bladder is normally free of bacteria (sterile). However, bacteria may be present in the bladder but not cause inflammation or symptoms of an infection. This is called asymptomatic bacteriuria and is not cystitis.

Cystitis can be complicated or uncomplicated. Uncomplicated cystitis is a bladder infection in a healthy person with a structurally and functionally normal urinary tract. A complicated bladder infection is one that occurs in association with factors that increase the chance of developing a bacterial infection and decrease the chance of antibiotic therapy being effective. Such abnormalities include obstruction from stones, congenital blockages, urethral strictures, and prostate enlargement.

What causes bladder infections?

All urinary tract infections are the result of interactions between the infecting organism (bacteria, yeast, virus), the number of the organisms that are present in the bladder, and the body’s ability to fight off the organism (host defense mechanisms).

The most common way bacteria gain access to the urinary system from outside is through the urethra (the tube that allows urine to pass from the bladder to outside of the body).

  • The most common source of bacteria that cause UTIs is from the stool.
  • In women, the bacteria from the stool travel first to the vagina and then enter the urethra.
  • Sometimes bacteria may enter the bladder via the urethra from nearby skin.
  • In general, women are more susceptible to bladder infections due to their shorter length of urethra.
  • In the first year of life, boys have a higher risk of UTIs, but thereafter girls have a higher risk that persists in adulthood.

In terms of specific bacteria, E. coli (Escherichia coli) is by far the most common organism responsible for bladder infection or cystitis. Staphylococcal (staph) organisms (from skin) and other gut bacteria (Proteus, Klebsiella, Enterococcus) are other bacteria that can cause cystitis and other forms of urinary infections. The type of organism causing the infection can vary with the individual’s age. For example, Staphylococcus saprophyticus, a skin bacteria, causes approximately 10% of symptomatic bladder infections in young sexually active women, whereas it rarely causes bladder infections in males and elderly individuals.

Rarely, bladder infection can be caused by a fungus. Candida is the most common fungus to cause bladder infection. Candida infections of the bladder and urinary tract are much less common than bacterial infections. Bladder infections from Candida can occur in patients whose immune system is weakened, individuals who have been treated with powerful antibiotics for other infections, and individuals who have had indwelling urinary catheters.

Viruses can rarely cause bladder infections. Viral cystitis can occur in individuals after bone marrow transplantation and in other individuals with a weakened immune system (immunocompromised individuals). Adenovirus can cause bladder infections and BK virus is another virus that can cause bladder infections in individuals who have undergone bone marrow transplantation.

Medically Reviewed by a Doctor on 9/25/2017

Source: MedicineNet.com
https://www.medicinenet.com/bladder_infection/article.htm

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