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Urinary Tract Infections

Urinary Tract Infections - Causes and Risk Factors

In most cases of uncomplicated cystitis the Escherichia coli is involved. This bacteria is present in 70-95 percent of both upper and lower UTIs. Other common pathogens are Enterococcus faecalis, Klebsiella species, Proteus species and yeast.

What are the predisposing factors?

The largest group of patients with UTIs is that of adult women. Women are more prone to UTIs than men because in females, the urethra is much shorter and closer to the anus.

Other predisposing factors include:

1. Menopause
Rates of UTIs are higher in postmenopausal women for a few reasons. For one, the presence of bladder or uterine prolapse can cause incomplete bladder emptying and stasis (reduced or stoppage flow) of urine which in turn promotes the growth of pathogens. Also, the loss of oestrogen after menopause leads to changes in the vaginal flora, especially the loss of lactobacilli, and increases your susceptibility to infection.

2. Sexual activity
UTIs are very common in women aged 18-30 years as it is associated with coitus (the so-called ‘honeymoon cystitis’). In this age group, sexual intercourse is the cause of 75 to 90 percent of bladder infections, with the risk of infection being related to the frequency of sex. The use of spermicides and diaphgrams for contraceptive purposes further increases the risk of UTIs as it causes a change in the vaginal flora and eradication of the vaginal lactobacilli.

3. Recent instrumentation of the urinary tract (e.g. catheterisation, cystoscopy, urodynamic studies) The insertion of foreign instruments into the urinary tract promotes the translocation of bacteria colonised around the peri-urethral area into the bladder and other parts of the urinary tract. This increases the risk of developing bacteruria (presence of bacteria in the urine) in significant numbers eventually leading to a UTI.

4. Foreign bodies (e.g. catheters, urinary stones) Urinary catheters are the most important risk factors for bacteriuria. Catheters introduce organisms into the bladder and promote colonisation by providing a foreign surface for bacteria to adhere to and by causing irritation of the bladder mucosa. 80 percent of UTIs that occur while in hospitals or healthcare institutions are related to urethral catheterisation, and 5-10 percent are related to manipulation of the genito-urinary tract. Urinary stones similarly irritate the bladder as well as provide a nidus for bacteria to adhere to, thereby increasing the risk of developing a UTI.

5. Neurological disorders, drugs or pelvic organ prolapse
These conditions may cause incomplete emptying of the bladder, thereby promoting stasis of urine which increases the risk of UTI development.

6. Medical conditions (e.g. diabetes) Diabetes leading to glycosuria (sugar in the urine) makes for fertile breeding ground for bacteria. A study showed that 9.4 percent of patients with Type 2 diabetes had a UTI compared to only 5.7 percent of people without diabetes.

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The information provided is not intended as medical advice. Terms of use. Information provided by SingHealth

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