What are urinary tract infections?

A urinary tract infection (UTI) is an infection anywhere in the urinary tract. The urinary tract includes the kidneys, ureters, bladder and the urethra.

Anatomy of the kidneys.

Urinary system and kidney anatomy.


UTIs are more common in women than men because they have a shorter urethra, which makes it easier for micro-organisms to enter the urinary tract. The most common cause of a UTI is Escherichia coli (E. coli) bacteria, which are normally present in stools (faeces). Other bacteria known to cause UTIs include KlebsiellaProteus mirabilisPseudomonasStreptococci, and Staphylococcus aureus. In adults, sexually-transmitted infections (STIs), such as chlamydia and gonorrhoea, can also lead to UTIs.

UTIs can also be caused by Candida albicans, a fungus that commonly causes vaginal thrush, especially if it associated with the use of a urinary catheter.

Conditions that affect the flow of urine, such as kidney stones and ureteral reflux (in which urine travels back up the ureter towards the kidney), increase the chances of developing a UTI.

Risk factors

Risk factors for UTIs include:

  • Gender – females are more commonly affected than males;
  • Menopause;
  • Diabetes;
  • Kidney stones;
  • Bowel incontinence;
  • An enlarged prostate gland, narrow urethra, or anything blocking urine flow;
  • Having a urinary catheter;
  • Brain or nervous system problems that make it difficult to empty the bladder;
  • Pregnancy;
  • Atrophic vaginitis due to menopause;
  • Using certain contraceptives, such as spermicide or diaphragms;
  • Having multiple or new sexual partners;
  • Having had a UTI in the past 12 months, and;
  • Surgery involving the urinary tract.

Signs and symptoms

UTIs usually start in the bladder and/or prostate (in men), and can then spread to the kidneys, or even into the blood (sepsis or bacteraemia). Symptoms of a UTI differ depending on whether it occurs in the bladder, prostate or kidney.

Symptoms of a bladder infection (cystitis) can include:

  • A strong or foul urine odour;
  • Cloudy urine;
  • Frequent and urgent urination;
  • Pain or a burning sensation while urinating;
  • Pain or pressure in the lower back or pelvis;
  • A minor fever, and;
  • Blood in the urine.

If the infection involves the prostate (prostatitis) in a male, symptoms can include:

  • Fever;
  • Backache, and;
  • Pain between the anus and scrotum.

Symptoms of a kidney infection (pyelonephritis) include:

  • Chills and shaking;
  • Fever and warm or reddened skin;
  • Fatigue;
  • Severe abdominal pain;
  • Nausea and vomiting;
  • Confusion or other mental changes (particularly in the elderly), and;
  • Severe pain in the side, back or groin area.

Methods for diagnosis

Urine culture

A urine culture is the gold standard for diagnosing UTIs. A diagnosis is usually made on the basis of urine culture results and the presence of symptoms. Since this test can take a few days to produce results, your doctor may prescribe antibiotic treatment before the test results are in.

Your doctor may also perform a rapid test (known as a dipstick urine test) to check whether there are any features of a UTI. This test is often used only to support suspicion of a UTI, and it cannot be entirely relied upon for a diagnosis.

Urine collection

Urine is often collected in what is called a ‘clean catch’ or ‘midstream’ specimen. This requires a small amount of urine to first be passed before urine is collected in a sample container. 

Another collection technique involves inserting a catheter into the urethra to draw urine directly from the bladder. This can be helpful in people who have no bladder control, or who are unable to follow instructions to give a urine sample.

Container used to collect urine for analysis.

Urine testing can provide a rapid and reliable diagnosis of an infection such as a UTI.

Other tests

Imaging tests, including ultrasound, computerised tomography (CT) scan and cystoscopy, may be performed if you have recurrent infections, or if any abnormalities in the kidneys, bladder or urethra are suspected. A digital rectal exam may also be performed if infection of the prostate is suspected in men.

Types of treatment

UTIs generally require treatment to prevent the infection spreading to the kidneys (pyelonephritis) or into the blood (sepsis). Bacterial infections are treated with antibiotics, usually taken as tablets, for several days. It is important to also drink plenty of water during a UTI, to help flush micro-organisms from the urinary tract. Symptoms improve within a day or two, but it is important to finish the full course of antibiotics as prescribed by your doctor, otherwise the infection may return.

You may also be advised to take medication to help with the burning sensation during urination. These medications help to neutralise the pH balance of the urine so that it does not burn the inflamed urinary tract. Depending on the type you take, the colour of your urine may change from orange or red. These medications are not meant to be taken for more than two days, unless advised by your doctor.

Kidney infection

Kidney infection is usually treated with intravenous antibiotics. If you are otherwise well, you may be allowed to stay at home and continue on oral antibiotics after the initial intravenous dose. However, if symptoms worsen or you are not improving, it is important you promptly see you doctor. If you are pregnant, or have severe pain and a high fever, you will likely be hospitalised and given intravenous antibiotics and fluids. When you improve, you will be able to go home and switch to oral antibiotics

Fungal infection

Infection of the upper urinary tract or widespread (systemic) infection with Candida albicans, a type of fungus, is treated with antifungal medication. Antifungal medication is not normally recommended if the infection is only associated with a catheter and not causing any symptoms. However, a change of the catheter is recommended. 

Potential complications

Complications are rare when UTIs are treated promptly. However, if left untreated, UTIs can cause sepsis, kidney abscess, swelling of the kidneys, and reduced kidney function and failure. These complications are also more likely in recurrent infections and the risk of sepsis is higher in people who are immunocompromised due to conditions, such as HIV/AIDS, or treatments such as chemotherapy. It is relatively common for UTIs to return and the use of preventative antibiotics is controversial. Preventative antibiotics, if used, are generally reserved for people who have very frequent or severe UTIs. The risks of antibiotic resistance and side effects need to be balanced against the benefits of preventing the infections.


Most UTIs are successfully treated with antibiotics. It is important to finish the prescribed course of antibiotics to prevent the return of infection.


Drinking plenty of fluids and urinating soon after sex may help reduce your risk. Women who get recurrent UTIs as a result of using spermicide or diaphragms can use alternative types of contraception. 

Last Reviewed: 03/10/2018

Reproduced with permission from Health&.