How does a urinary tract infection develop and how are they treated?

What is a UTI or urinary tract infection?

Cystitis is the name given to inflammation of the urinary tract. Its origins are in the Greek terms “cyst,” meaning bladder and “itis,” meaning inflammation. Where this inflammation is caused by infection, this is known as a Urinary Tract Infection or UTI.

A human urinary tract consists of:

  • The kidneys – where the urine is produced
  • The ureters – there are two ureters, one on each side of the body, and their role is to transport the urine from the kidneys toward the urine bladder
  • The bladder – a sac-like organ which collects the urine produced by the kidneys
  • The urethra – a tube through which the urine produced in the kidneys and collected in the bladder is eliminated from the body
Urinary-system Image

Women during their sexually reproductive and menopausal years are more likely to suffer from UTIs, however men, infants, children, adolescents and the elderly also get UTIs.

There’s also not enough research to understand why some people never experience a UTI, why some people have one or two infections and why some people develop chronic infections.

But research into the urinary microbiome – the community of microbes that inhabit the urinary tract – and the female urinary and vaginal microbiome is ongoing.

More about the urinary microbiome.

What can cause a urinary tract infection?

A UTI usually occurs when infection causing bacteria are introduced via the urethra or can be due to an upsurge of existing bacteria in the bladder or urethra. This is known as uncomplicated cystitis

But a UTI may also result from physical abnormality, neurological conditions or obstruction and this known as complicated cystitis.

There are different types of urinary tract infection

The type of infection depends on which part of the urinary tract is infected – the upper or lower part of the urinary system. The Lower Urinary Tract system (LUTS) includes infections of the urethra and the bladder. Infections of the Upper Urinary Tract include the ureters and the kidneys.


A bacterial infection of the urethra, the hollow tube that drains urine from the bladder to the outside of the body. Often associated with sexually transmitted diseases (STD).


A bacterial infection in the bladder that often has moved up from the urethra.


An infection of the kidneys that is usually a result of an infection that has spread up the tract via the ureters, or from an obstruction in the urinary tract. An obstruction in the urinary tract causes urine to back flow into the ureters and kidneys.These can be serious, as there is a risk of affecting the kidneys and, in some cases, this can also lead to kidney failure.

What are the symptoms of a lower urinary tract infection?

Some or all of these symptoms may occur:

  • A frequent and pressing urge to pass urine, while only being able to void small amounts of urine
  • A hesitant or intermittent flow of urine
  • A need to pass urine many times a day – this can rise to 4-6 times an hour on bad days
  • Pain, usually burning or stinging, when passing urine (known as dysuria) in the bladder or urethra
  • Having to get up several times in the night to go to the toilet
  • Cloudy urine or blood in the urine (haematuria)
  • A strong, sweet or “fishy” smell to the urine – bacteria can change the odour of urine
  • For women, pain and inflammation across the pubic bone, pelvic floor and lower abdomen. Pain may radiate into the vagina or along the vulva.
  • For men, pain and inflammation radiating into the rectum. Pain may travel down the legs as well.
  • A pressure sensation in the lower abdomen and pelvis – due to the inflammation of the bladder pressing against the other pelvic organs.
  • Fever, feeling generally unwell, a dull ache in the lower abdomen and back. These symptoms may mean the infection has spread to the kidneys
  • Emotional distress and brain fog/confusion. This can particularly affect the elderly.
  • Discharge may accompany the above symptoms in the case of urethritis

What are the symptoms of an upper urinary tract infection?

Some or all of these symptoms may occur:

  • upper back and side (flank) pain
  • high fever
  • shaking and chills
  • nausea
  • vomiting
  • blood or pus in the urine

What causes a UTI to develop?

There are many causes from which a UTI can develop, these can include:

  • After sexual intercourse (anal or vaginal), through a new sexual partner (size matters sometimes), poor post sex hygiene or using sex toys that have not been previously thoroughly cleaned or sterilised
  • Misshapen bladder or structural/physical anomalies within the urinary tract
  • Urinary tract obstructions or blockages, such as an enlarged prostate or kidney stones
  • Investigative surgery of urinary tract including cystoscopy/bladder or urethral stretch /hydrodistension of the bladder or bladder biopsy
  • Childbirth
  • Diabetes particularly those diagnosed with type 2 diabetes
  • Injury or paralysis to the spinal cord reducing/stopping signals from the urinary tract to the brain to empty the bladder. This condition is known as neuropathic or neurogenic bladder and those affected need to self catheterise or have an indwelling catheter to empty the bladder.
  • Vaginal/bowel prolapse preventing complete emptying of the bladder
  • After being catheterized or where an indwelling catheter is in place
  • Sexually transmitted diseases (for urethritis)
  • Pelvic surgery including mesh implant or hysterectomy
  • Menopause/Peri-Menopause/Premature Menopause
  • Being on certain birth control pills, using an IUD, diaphragm and spermicide usage
  • Personal hygiene including not wiping from front to back after bowel movements. This can particularly affect children and the elderly

What if it’s not a UTI?

Some UTI-like symptoms may not be caused by a urinary tract infection but may be due to a sexually transmitted disease such as Chlamydia, Herpes, Gonorrhoea or a fungal infection such as Candida or thrush. Mycoplasma or Ureaplasma can also cause Urethritis like symptoms.

If you are in any doubt ask your GP or local Sexual Health Clinic for examinations and tests to exclude:

Other causes of lower urinary tract symptoms can include:

  • prostate enlargement in men
  • bladder or kidney stones
  • cancer of the kidneys, bladder and/or prostate
  • bladder detrusor muscle weakness and/or instability
  • prostatitis
  • urethral stricture
  • pelvic floor pudendal nerve problems
  • Trauma to the pelvic floor following falls, childbirth or surgery causing nerve dysfunction

Your GP should refer you to a specialist for further investigations and tests, particularly if there is reason to suspect cancers of the urinary tract.

How is a UTI currently diagnosed and treated?

Diagnosis for a urinary tract infection is usually done via the GP surgery or a walk in clinic.  After you explain your symptoms, you may be asked to provide a mid-stream urine sample (MSU) and given a sample pot to collect it in. A mid-stream urine sample means you don’t collect the first or last part of urine that comes out but only the middle part of the stream into the sample pot. If in any doubt, ask your GP or nurse to explain the procedure.

What dipstick tests look for

A urinary dipstick is then “dipped” into the sample. This dipstick test strip is made of paper and can have up to 10 different chemical pads or reagents which react (change colour) when immersed in, and then removed from, a urine sample usually after around 60 seconds. The dipstick analysis includes testing for the presence of:

  • White blood cells (known as Leukocytes) – only a few white blood cells are normally present in urine. When these numbers increase, the dip test will become positive. This indicates that there is inflammation in the urinary tract or kidneys and the body is excreting more white blood cells. White blood cells also produce antitoxins that neutralise the toxins released by bacteria.
  • Red blood cells – the bladder can bleed due to severe inflammation and the constant urination caused by a UTI. Some people can feel a “razor blade sensation” when urinating during a UTI attack.
  • Protein – the presence of protein can indicate a possible kidney infection as only trace amounts normally filter through the kidneys. Other causes of protein in the urine can include kidney disease, dehydration,
  • Nitrates– Some bacteria that cause a UTI make an enzyme that changes waste urinary nitrates to nitrites. However not all bacteria are able to produce this enzyme.

Any evidence of these in the urine on a dipstick test may indicate an infection.

It is important to note that in addition to possible bacterial infection, a positive White Blood Cell (Leukocyte) test may also indicate chronic kidney inflammation caused by a kidney stone, a tumour of the kidneys, bladder or urethra, infections such as chlamydia or other sexually transmitted diseases and fungal infections such as Thrush. Red Blood Cells in the urine may be due to menstruation, haemorrhoids, kidney, bladder or urethral cancers, enlargement of the prostrate in men; kidney stones or injury to the kidneys. Protein in the urine may also be due to dehydration, diabetes, kidney disease and pregnancy.

Depending on the dipstick analysis, the GP can send the sample to a laboratory for further analysis. They will discuss your symptoms with you and take into account other current and previous health issues and any family disease history.

Common treatments for a UTI

You may be given a short course – one, three or five days – of antibiotics which can start before any laboratory results come back, particularly if symptoms are acute and noticeable blood, protein and nitrates are found in the dipstick test.

GPs may advise instead of antibiotics, if symptoms are not severe or the dipstick result is negative, to use over the counter cystitis relief sachets, pain relief, drink cranberry juice, wipe front to back after passing a bowel movement and to drink plenty of water.

If your sample has been sent off to the laboratory, the GP should receive the results within 48-72 hours. They may prescribe antibiotics then if it is positive or change the antibiotic initially prescribed before the urine sample analysis result.

Always ask for a paper copy of these results even if they are negative. They give important clues to signs of infection even if no bacteria were grown.

Find out how to interpret your urine test result.

What happens if you don’t get better?

These methods of diagnosis and treatment are based on acute attacks – an infection that can be easily resolved with antibiotics or self-treatment. Depending on your immune system response to prevent the infection worsening and the type of antibiotics prescribed, short, acute attacks can settle quickly.

But some people continue to have UTI symptoms after their initial treatment ends or find their symptoms soon return. This could be because

  • The self-help treatment hasn’t worked
  • The dipstick or urine analysis in laboratory is inconclusive (the lab report can state mixed growth, low growth, contaminated sample or negative growth)
  • The short course of antibiotics hasn’t cleared the infection from the urinary tract

At this point you could be prescribed another short course of low dose antibiotics.

Do you keep on getting UTIs or feel like it’s never really gone away?

We explain how an acute UTI can turn into a chronic infection.

Read about the issues with tests, diagnosis and treatments.