Urinary Tract Infections (UTI)

by Dr Milton Lum

The urinary system comprises the kidneys, which are bean-shaped structures in the lower back, and the ureters, which are tubular structures that connect the kidneys with the bladder, a bag-like structure in the lower abdomen that stores urine prior to its excretion from the body through the tubular urethra.

One of the main functions of the urinary tract is to get rid of waste products produced by the body. The urine produced in the kidneys is normally sterile.

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Urinary Tract Infections (UTI)

Urinary tract infections (UTI) involve the presence of microbial organisms in the urinary tract. They are one of the commonest infections affecting humans. UTI is very common in females, the overall incidence being about 50 times more than in males. UTI is uncommon in males below 60 years of age. However, the situation in older males and females is different in that the incidence is about the same.

There is a range of UTI. It may be an infection involving the bladder (cystitis) or it may involve the kidneys (pyelonephritis).

Microbial Colonisation

UTIs occur as a result of 3 processes, i.e. microbial colonisation of the lower urinary tract with ascending spread, blood-borne spread and peri-urogenital spread. The factors that impact upon these processes include the virulence of the organisms and the defences of the affected person.

Intestinal bacteria possess characteristics that enable them to adhere to, multiply in, and colonise the urinary tract, leading to UTIs. Most UTIs are due to bacterial ascent of the urinary tract.

The body protects itself from microbial colonisation by mechanisms that include the unidirectional flow of urine, antimicrobial properties of the urine, and surface antibodies that reduce microbial adherence and invasion. When these mechanisms are impaired, the likelihood of UTI is increased.

Bacterial Infection

Pyelonephritis is usually the result of bacterial migration from the bladder to the kidney. If the infection is uncomplicated, the area involved is the junction between the ureters and the kidney and the adjoining area (pyelocalyceal-medullary region).

If the infection becomes complicated, it would involve all regions of the kidney and may, in some instances, involve the blood stream (septicaemia) with bacterial spread to other parts of the body.

UTIs are categorised into either community or hospital acquired. The former are usually due to the bacterium, Escherichia coli (E. coli), which is found in the patient's bowels. Although E. coli is a common cause of the latter, other causative organisms include pseudomonas and staphlococci. It is common to have multiple organisms in hospital acquired infections with antibiotic resistance a common problem.


The symptoms of UTI differ depending on whether the lower urinary tract, i.e. bladder and urethra, or upper tract, i.e. kidney, is affected.

The symptoms that are suggestive of UTI include pain or a burning sensation when passing urine, urges to pass urine, lower abdominal discomfort or pain, urine that smells or appears cloudy or red, fever, and less often, back pain or nausea. Sometimes the symptoms are less specific and they include tiredness and confusion. It is advisable for anyone with these symptoms to seek medical attention.

Many people who have UTI do not have symptoms at all. That is why the urine is routinely examined in people who are at increased risk of UTI, e.g. pregnant women, diabetics, those using a urinary catheter, and those who have a congenital abnormality of the urinary tract.


Cystitis is an infection of the bladder, which causes burning sensation during urination and a frequent need to pass urine, including waking up at night to pass urine. However, many affected persons do not have symptoms, especially females and some senior citizens.

It has been estimated that about 20% to 40% of women will suffer from cystitis during their lifetime. The commonest organisms that cause cystitis are intestinal bacteria. They enter the urethra and ascend into the bladder.

One of the main reasons why females are more susceptible to cystitis is the fact that their urethras are short, thereby predisposing them to infection from intestinal microbes, which are found in the anus and rectum that are nearby.

The likelihood of cystitis is increased when there is incomplete emptying of the bladder, which leads to stagnation of urine. There are several causes for this, including immobility, poor bladder control, and medicines like antidepressants.

Several conditions increase the likelihood of cystitis including :

* Toilet hygiene is an important factor. As the anus is near the urethral opening, the likelihood of exposure to intestinal microbes is increased, particularly when females clean and dry themselves from back to front after doing their 'business'. By cleaning and drying themselves from front to back, females will decrease their exposure to intestinal microbes.

* Pregnancy increases the likelihood of cystitis. Many pregnant women with cystitis do not have symptoms, which is one of the reasons why the urine of pregnant women is checked at every antenatal consultation. Untreated or inadequately treated cystitis in pregnant women increases their risk of pyelonephritis and pre-term labour.

* 'Honeymoon cystitis' is associated with frequent sexual intercourse. The thrusting in vaginal intercourse traumatises the urethra, thereby increasing the likelihood of cystitis.

* Post-menopausal women are more prone to cystitis as the lack of female hormones causes a general atrophy of the urogenital tracts.

* Sexually transmitted infections (STI) like chlamydia and gonorrhoea may give rise to symptoms that are similar to cystitis. There may be other symptoms in affected females, which may include vaginal discharge, vulval irritation and bleeding after sexual intercourse.

* An enlarged prostate in older males prevent complete emptying of the bladder, leading to stagnation of the urine. Infections of the prostate (prostatitis) can also lead to symptoms similar to cystitis. The urethra passes through the prostate, which is a walnut shaped gland just below the bladder.

* Narrowing of the urethra (stricture), which can arise as a consequence of infection and repeated instrumentation, prevent complete emptying of the bladder, leading to stagnation of urine.

* Congenital abnormalities of the urinary tract prevent complete emptying of the bladder, leading to stagnation of urine. This cause has to be excluded in boys and young men who have repeated episodes of UTI.

* Bladder tumours, both cancerous and non-cancerous, also increase the likelihood of incomplete emptying of the bladder.

* Catheters inserted, for various medical and surgical conditions, to drain urine from the bladder increase the likelihood of UTI, which are usually without symptoms. Changing of the catheter may traumatise the bladder and urethra and lead to not only cystitis but also infections spreading to the kidneys and the bloodstream.


Pyelonephritis is an infection of the kidney(s). The symptoms include frequent passing of urine, pain when passing urine, feeling the urge to pass urine, aches in the back, groin, and side of the body, fever, blood and/or pus in the urine, nausea, and vomiting.

There are several conditions that increase the likelihood of pyelonephritis.

They include cystitis, stones in the urinary tract, prostatic enlargement, abnormalities in the urinary tract that impair urine flow, neurological conditions like spina bifida and multiple sclerosis, use of urinary catheters, use of instruments to examine the bladder and/or ureters i.e. cystoscope and ureteroscope, and surgical procedures on the urinary tract.

Sometimes pyelonephritis can result from blood borne spread of micro-organisms.


Most UTIs are uncomplicated, particularly when they are adequately treated. However, complications can arise, especially when the UTI is severe or recurrent. Severe infections can lead to bacterial spread into the blood stream (septicaemia) with spread of infection to other parts of the body.

The kidneys may stop functioning, a condition called renal failure. This may be acute, which is temporary, or chronic, which is permanent.


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