A urinary tract infection is an infection involving part or all of the urinary tract. The effects of the infection depend on the interaction between the bacterium and the host’s defence mechanisms.

If the brunt of the infection is situated in the bladder, the symptoms tend to be of a local nature and the disease is called cystitis, or a lower urinary tract infection. Infection involving mainly the kidney is called an upper urinary tract infection. The symptoms tend to be of a more systemic nature, such as fever, chills and a fast heart rate.

The division between upper and lower urinary tract infection is somewhat arbitrary, since the infection enters the system by an ascending route via the urethra (the tube connecting the bladder to the outside) in both cases. The bacterium E. coli are responsible for 80 percent of urinary tract infections.

TB of the urinary tract, kidney abscess and infections of the male genital organs are dealt with in related topics (see below). Infections of the female genital tract are not regarded as urinary tract infections.

Causes



    • A urinary tract infection is the result of an interaction between the bacterium and the patient. Aggressive bacteria are able to overcome normal host defence mechanisms.

    • Less aggressive bacteria can lead to significant infections in patients with abnormal urinary tracts or compromised immunity.

    • Most bacteria reach the urinary tract via the ascending route, traversing the urethra, bladder and sometimes the ureters up to the kidneys. The main source of these bacteria is the patient’s own large intestine. The female urethra is short and situated close to the faecal reservoir, explaining the much higher incidence of urinary tract infections in females compared to males.

    • E. coli is responsible for 85 percent of community acquired and 50 percent of hospital acquired urinary tract infections. In diabetics and immuno-compromised patients, fungi and certain viruses account for a significant percentage of urinary tract infections.

    • Certain special organisms such as Mycobacterium tuberculosis (which causes TB) and Staphylococcus aureus (which can cause a renal abscess) reach the kidneys via the bloodstream rather than the ascending route.



Symptoms

Upper urinary tract infection



    • Fever

    • Chills and shakes

    • Vomiting

    • Pain in the loin



This infection is usually unilateral, affecting only one kidney. Bilateral involvement is less common, but not impossible. Despite the presumed ascending route of infection via the urethra, bladder and ureter to the kidney, bladder symptoms are usually non-existent or mild.

Lower urinary tract infections



    • The frequent passage of small amounts of urine.

    • A great desire to urinate, and with difficulty postponing urination.

    • If there is pain and burning while passing urine.

    • When there is blood in the urine.

    • Pain in the lower part of the abdomen, just above the pubic area.



Patients with lower urinary tract infection have severe bladder symptoms, but tend not to be systemically unwell. Fever, rigours and a fast heart rate as seen with upper urinary tract infection are usually absent. Note that blood in the urine can be caused by other more sinister causes than cystitis, such as bladder cancer. Blood in the urine should not be assumed to be due to cystitis unless other more serious causes have been excluded.

Prevalence



    • Tract infections are much more common in women than in men.

    • A recent survey found almost half of Australian women are unaware that urinating immediately after sex can help prevent a urinary tract infection, according to Kidney Health Australia.

    • It is estimated that with one in two women and one in 20 men in Australia are expected to experience a UTI at some point, with varying degrees of severity according to how far the infection spreads.

    • The prevalence of urinary tract infections in young women is 30 times that of young men.

    • With increasing age, more relatively older men develop urinary tract infections.

    • Twenty-five to 30 percent of women between the ages of 20 and 40 years have had urinary tract infections.

    • The prevalence of bacteria in the urine also increases with hospitalisation and concurrent disease such as diabetes. About 40 percent of patients with urinary tract infections have a recurrence within one year.



Who’s at risk?


Risk factors can either be general, usually affecting the immune system, or local, in which case normal emptying of the bladder is impaired. General risk groups include:

    • Infants and old people have less resistance to infection.

    • Diabetes increases the risk for urinary tract infections.

    • Any cause of impaired immunity such as malnutrition, HIV/AIDS or cancer.



When to see a doctor


Not all self-diagnosed urinary tract infections turn out to be urinary tract infections after all. Some sinister and other less serious conditions can masquerade as urinary tract infections. The role of the health professional includes making an accurate diagnosis, treating the acute event and investigating patients for underlying predisposing factors.

The following patients with a suspected urinary tract infection should see a doctor urgently:

    • All children

    • All cases of suspected kidney infection

    • All cases with blood in the urine

    • Anybody with only one kidney

    • Previous history of stones

    • Previous history of kidney surgery

    • Anybody with a high fever

    • Vomiting

    • Severe pain

    • Anybody with pain in the right lower abdomen who still has an appendix

    • All pregnant females

    • No response to antibiotics after two to three days of treatment



Following the (successful) treatment of the acute event, the following patients should be investigated for possible underlying predisposing causes:



    • All children

    • All males

    • All cases of pyelonephritis

    • Females with more than one attack of cystitis

    • Everybody with blood in the urine (at any stage)

    • Anybody with a urinary tract infection which seems difficult to eradicate with standard antibiotics



Diagnosis


The diagnosis is made by means of a history, physical examination and special investigation of the upper and/or lower urinary tract infection by means of a history, physical examination and special investigations (tests).

Treatment


Cranberry has been popularly used to treat mild urinary tract infections. Similarly, alkalinising urine through diet is another popular natural remedy for urinary tract infection, so use of liquid chlorophyl is recommended by many dieticians and naturopaths to help reduce the incidence and severity of UTI's.

Mild to moderate uncomplicated lower infection will probably resolve with or without treatment, but conservative measures include increased oral intake of fluids and agents to alkalinise the urine. Antibiotics expedite recovery.

Upper infections are not suitable for home treatment. Some patients with recurrent urinary tract infections are issued with antibiotics, which they take as soon as symptoms develop. They are usually expected to take a urine sample prior to commencement of treatment.

Surgery


Surgery has no primary role in the treatment of urinary tract infections. Some of the complications of infections are treated by surgery, such as the drainage of kidney abscesses. Some of the underlying abnormalities that predispose a patient to infection can be corrected surgically, such as the removal of stones or the alleviation of obstruction.

Prevention



    • Adequate fluid intake to ensure the passage of 1½ to 2 litres of urine per day. There is no benefit in excessive fluid intake.

    • Women should always wipe from front to back after passing stool.

    • Women should empty the bladder after sexual intercourse.

    • Avoid spermicidal creams and diaphragm contraceptives as both these are associated with a higher incidence of urinary tract infections.

    • Regular intake of cranberry juice has traditionally been used to give a protective effect. A substance in cranberries prevents the adhesion of bacteria to the lining of the urinary tract.

    • Daily low dose prophylactic antibiotics reduce the rate of infection in patients suffering from recurrent infections. However, this does not alter the underlying propensity to develop infections once the prophylaxis is stopped.



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