What is a UTI? Causes of Urinary Tract Infections

UTI is the acronym for urinary tract infection. This refers to an infection of the urethra, bladder, ureter and/or kidney. Most UTI’s are due to bacteria but other microbes may also be responsible although this is rare. The action of the causative microbe results in inflammation of the organ or part of the organ that it has infected leading to a host of symptoms like :

  • pain/burning when urinating (dysuria)
  • frequent urination
  • urging
  • incontinence
  • discharge (foul odor)
  • blood in the urine (hematuria)
  • cloudy urine
  • fever
  • pelvic pain, tenderness

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Different terms are used to indicate inflammation due to an infection of certain parts of the urinary tract.

  • Urerthritis ~ urethra
  • Cystitis ~ bladder
  • Ureteritis ~ ureter
  • Pyelonephritis ~ kidney

In men, the prostate gland may also be infected and this is referred to as prostatitis.

It should be noted that these terms may be used for other causes of inflammation. For example : interstitial cystitis is the inflammation of the bladder due to non-infectious causes. Apart from the symptoms of a UTI, a urinalysis will confirm the presence of microorganisms and a culture will help assist with identifying the causative organism.

What Causes UTI’s (Urinary Tract Infections)?

Bacteria colonize the distal part of the urethra even in a healthy person. This does not cause a UTI unless some contributing factor like obstruction or reduced output of urine, trauma to the urinary tract and changes in the composition of urine allows for bacterial spread.

Bacteria cause most urinary tract infections and enter through the urethra. The bacteria multiply in the bladder and can infect the ureters and eventually the kidneys. Bacterial infections that start in the kidneys are more serious as it means that the causative microorganism has reached the kidney through the bloodstream and there is a greater risk of septicemia.

The most common bacterial causes of a UTI include :

  • Escherichia coli (E.coli is the most common cause)
  • Staphylococcus saprophyticus
  • Proteus mirabilis

Fungal infections are more likely to affect the bladder and kidney and often reach the kidney through the bloodstream.  It does sometimes start in the lower urinary tract (urethra and bladder) as a result of the insertion of a catheter when treating other urinary tract conditions.

The most common fungal cause of a UTI is due to the Candida species (spp)  although other species (example : Cryptococcus spp, Aspergillus spp) may also be responsible. Fungal urinary tract infections like renal candidiasis is rare in a healthy person and most cases are seen in immunocompromised patients (HIV/AIDS, uncontrolled diabetes, cancer, chemotherapy).

Other Infections of the Urinary Tract

Many sexually transmitted diseases may cause a UTI including Neiserria gonorrhoeae, Chlamydia trachomatis, Trichomonas vaginalis and herpes simplex virus. Schistosomiasis (Schistosoma haematobium) or bilharzia  is an infection with a flatworm (fluke) which lodges in the bladder and causes significant damage to the lining of the bladder.

Related Articles

  1. What is Dysuria?
  2. What is Hematuria?
  3. What is Incontinence?
  4. Causes of Frequent Urination in Men, Women

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