The urinary system is composed of the kidneys, ureters, bladder and urethra, all of which play a role in removing waste from the body. Normally, urine is sterile and free of bacteria, viruses and fungi, although it does contain fluids, salts and waste products. An infection occurs when bacteria cling to the opening of the urethra (the tube that carries urine from the bladder to outside the body) and begin to multiply.

Although the urinary system is designed to keep out such microscopic invaders, the defenses sometimes fail. When this happens, bacteria may take hold and grow into a full-blown infection that affects the inner tissue lining of the urinary tract. Although any part of the urinary system can become infected, most infections occur in the lower urinary tract - the bladder and urethra.

An average 80 per cent of urinary tract infections (UTI) are caused by E.coli bacteria and the remaining ten per cent by Chlamydia, Mycoplasma, Neisseria gonorrhoeae and others such as Proteus or Staphylococcus ("Staph").

While a UTI in the bladder only is painful and annoying, serious consequences can occur if the infection spreads to the kidneys, which is why it is so important to nip it in the bud quickly and effectively.

• UTIs are more common in infant boys than girls during their first year, but then progressively become more prevalent in girls, especially those of school-going age.

• Women are at greater risk of developing UTI than men. One woman in five develops a UTI during her lifetime and many suffer from recurring UTIs.

• UTIs are not as common in men but can be very serious when they do occur. Older men can be troubled by UTIs due to prostate complications.

Symptoms of UTI

The urinary tract reacts to a bacterial infection in much the same way that the upper respiratory system reacts to a cold virus. The tissues become inflamed, irritated and swollen. Just as it's hard to breathe through swollen and inflamed nasal passages, so swollen and inflamed urinary ducts can partially obstruct the normal flow of urine, making it painful and difficult to urinate. Sufferers of UTI are plagued by a strong, frequent urge to "go", which is accompanied by burning and painful urination.

The urine is strong-smelling and appears cloudy, or bright pink or cola coloured - a sign of blood in the urine. Other symptoms include upper back and side pain, high fever, shaking and chills, nausea and vomiting. Pelvic pain in women and rectal pain in men is also common.