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What is a urinary tract infection (UTI)?

Urinary tract infections (UTIs) are infections (usually caused by bacteria) that can occur anywhere in the urinary tract. They are named according to their location in the urinary tract and symptoms differ depending on where they occur. Normally the urinary tract (i.e. the kidney, ureters and bladder) is sterile or free of any organisms within the urine.

Urinary tract infection occurs most commonly in the bladder (also known in layman’s terms as “cystitis”). Cystitis is a general term indicating inflammation of the bladder and there are many other potential causes of cystitis other than a UTI.

Most UTIs are caused by bacteria that are normally located in otherwise healthy people in the bowel and skin of the perineum (the area of skin surrounding the vagina and back passage).

Some bacteria are more “uropathogenic” i.e. they have features that make it easier for them to enter the urinary tract and cause infection.

In which parts of the Urinary Tract can an Infection Occur?

Lower urinary tract infections are the most common type of UTI. These occur in the:

  • Bladder – in both women and men- also commonly known as “cystitis”
  • Urethra (the pipe draining urine from the bladder) – in both women and men called urethritis
  • Prostate in men - called prostatitis
  • Testis and epididymis (drainage system of the testis) in men- called epididymoorchitis

Upper tract urinary tract infections:

  • These infections are thankfully less common as they are more serious and can result in patients becoming severely unwell with septicaemia (entry of bacteria into the blood stream).
  • Urinary tract infection in the kidney is called pyelonephritis.

How common are Urinary Tract Infections?

  • About 1 in 3 women will have a UTI at some time in their life.
  • About 1 in 20 men will have a UTI at some time in their life.
  • Although men are less commonly affected by UTIs than women, they tend to have more severe UTIs which may potentially be associated with more structural problems in the urinary tract e.g.
    • Poor bladder emptying
    • Blockage of the outflow of urine from prostate enlargement

Why are Women more commonly affected By UTIs?

Women are more commonly affected by UTIs because of:

  • The female anatomy
    • The female urethra (urine pipe draining urine from the bladder) is short which allows easier entry of skin and surface bacteria into the bladder.
    • The female urethra is close to the vagina and back passage, which normally contain bacteria, and makes it easier for bacteria to enter the urinary system.
  • Sexual intercourse can make it easier for bacteria to stick to the urethra and then later enter into the bladder.
  • After menopause the drop in oestrogen levels causes changes in the tissues of the vagina and urethra that make them drier and make it easier for urinary tract bacteria to colonise or live in the area.

What is a recurrent Urinary Tract Infection (UTI)?

Recurrent urinary tract infection has been defined as:

  • 3 episodes of UTI within the last 12 month period or
  • 2 episodes of UTI within the last 6 months

Simple UTIs Versus Complex UTIs

UTIs can also be classified according to whether they are:

  • Simple – i.e. occurring in an otherwise normal urinary tract
    • These infections tend to be less severe and serious as well as easier to clear and more responsive to treatment
  • Complex – i.e. occurring in:
    • An abnormal urinary tract
    • In people with other factors that can make infection harder to clear such as with a compromised immune system