Urinary tract infections
Written by Tashi Maseland
Last Reviewed: August 2019
Review Due: August 2020
DEFINITION1
UTIs (Urinary Tract Infections) can be classified in a number of ways:
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Upper UTI - Pyelonephritis
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Lower UTI - Cystitis or Prostatitis
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Uncomplicated UTIs - Occur in otherwise healthy patients
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Complicated UTIs - Occur in men, pregnant women or patients with underlying functional or structural abnormalities of the urinary tract or other conditions which predispose to infection
AETIOLOGY2
Bacteria from the bowel and vaginal flora (typically anaerobes and gram-negative bacteria) are the most common organisms causing UTIs. E.coli accounts for the vast majority (75-90%) of cases.
risk factors3
Female sex
Presence of a foreign body (e.g. catheter)
Sexual intercourse
Spermicide use
Abnormal bladder function (e.g. neurological disease)
Urinary tract blockage (e.g. by stones or prostatic hypertrophy)
History of recurrent UTI
Post-menopause
Pregnancy
Underlying disease (e.g. diabetes mellitus)
SIGNS AND SYMPTOMS4
Urinary frequency
Dysuria
Urinary urgency
Suprapubic pain
Cloudy, blood-stained or pungent urine
Fever and flank pain (in pyelonephritis)
PATHOPHYSIOLOGY2
Pathogens colonise the urinary tract by one of two routes: ascending infection or haematogenous infection.
95% of UTIs are caused by ascending infection, whereby bacteria enter the distal urinary tract and ascend via the urethra to the bladder causing cystitis or to the kidneys causing pyelonephritis. Bacteria are normally flushed away by the passage of urine as the bladder empties. Urine stasis of any cause thus impairs the host defence against urinary tract colonisation.
Women are more susceptible to UTIs as they have a shorter urethra. The urethra is also in close proximity to the vagina and anus, both of which are colonised with bacteria. Sexual intercourse can spread bacteria to the urethra, making it a common condition in young females. Susceptibility to UTIs varies among women depending on a variety of host and bacterial factors.
Rarely, pathogens from a distal site in the body may spread to the kidneys from the bloodstream (haematogenous infection). This leads to involvement of the renal parenchyma.
Investigations5
A diagnosis of UTI can often be made clinically with appropriate history and examination findings. Further investigation may be of benefit in some patients.
Urinalysis
Urine dipstick may show evidence of nitrites, leukocytes or protein. A negative dipstick result does not exclude UTI, but significantly reduces the probability.
Mid-Stream Specimen of Urine (MSSU) Culture
A result of >10 colony forming units (cfu)/ml is typically diagnostic. The specimen can also be used to establish antibiotic sensitivities. A culture isn't typically required in non-pregnant women, but should be considered in children, men and pregnant women.
Blood Tests
FBC and CRP - For signs of raised inflammatory markers
Blood Cultures - If evidence of systemic infection
Imaging
Patients who fail to respond to treatment, have recurrent UTIs, or have unusual organisms/symptoms may require referral to urology for consideration of ultrasound, cystoscopy or CT.
5
TREATMENT6,7
Do not treat asymptomatic bacteriuria in men, catheterised patients and non-pregnant women.
Note that the below antibiotics guidelines are based on the NHS GGC antimicrobial handbook. Always consult local guidelines for the correct dosing and antibiotic information.
Non-Pregnant Women
Uncomplicated Lower UTI: Nitrofurantoin or Trimethoprim for 3 Days
Upper UTI without Sepsis: Ciprofloxacin or Trimethoprim for 7 Days
Upper UTI with Sepsis: IV Gentamicin for 3-4 Days or if eGFR<20 then Temocillin/Ciprofloxacin for 7 Days
Pregnant Women
Asymptomatic Bacteriuria: Nitrofurantoin or Trimethoprim for 7 Days
Lower UTI without Sepsis: 1st/2nd Trimester: Nitrofurantoin/Trimethoprim/Cefalexin for 7 Days, 3rd Trimester: Trimethoprim/Cefalexin
Upper UTI without Sepsis: Co-Amoxiclav or Trimethoprim for 14 Days
Upper UTI with Sepsis: IV Co-Amoxiclav +/- IV Gentamicin for 14 Day
Men
Uncomplicated Lower UTI: Nitrofurantoin or Trimethoprim for 7 Days
Prostatitis: Ciprofloxacin or Trimethoprim for 28 Days
Epididymitis/Orchitis: Ofloxacin for 14 Days
Upper UTI without Sepsis: Ciprofloxacin or Trimethoprim for 7 Days
Upper UTI with Sepsis: IV Gentamicin for 3-4 Days or if eGFR<20 then Temocillin/Ciprofloxacin for 7 Days
Catheterised Patients
Symptomatic Bacteriuria without Sepsis: Replace Catheter with Single Dose IV Gentamicin
Symptomatic Bacteriuria with Sepsis: Replace Catheter with Single Dose IV Gentamicin - Rx According to Sensitivities
EPIDEMIOLOGY7
UTIs are one of the most common conditions seen in primary care.
They are much more common in women than men, with roughly 10% of women over 18 experiencing at least one suspected UTI annually. Of the women who develop a UTI, 20% to 40% experience recurrent UTIs.