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Urinary Tract Infection

From Mediwikis


Urine is normally sterile whilst in the bladder. Urinary Tract Infections (UTIs) are more common in women, except in neonatal children, where they are more common in males. Recurrent UTIs are infections with different organisms, while relapse is further infection with the same organism.


Note that cloudy urine is not pathognemonic- can be due to dehydration.


Can be asymptomatic

  • Suprapubic ache
  • Dysuria (= painful urination)
  • Increased frequency
  • Pyrexia
  • Urine changes - Haematuria, cloudy urine, abnormal odour
  • Strangury (pain and feelings of urgency even when the bladder is empty)

Upper (Pyelonephritis)

  • Rigor
  • Vomiting
  • Fever
  • Confusion/delirium


Usual pathogen is E. Coli in the community, others include gram negatives, S. saprophyticus, Proteus spp., Adenoviruses, and Candida. UTIs can be associated with sexual activity ("honeymoon-cystitis"), Pregnancy/Menopause, Catheterisation.


  • Urine Dipstick shows Nitrites or leukocytes.
  • MSU- significant bacteriuria > 105 cfu/ml
    • Always send an MSU if the patient is a child, male, pregnant or immunosuppressed even if the dipstick is negative
    • Sterile pyuria (pus in urine but no bacteria grown on culture) may be due to TB, stones, tumours, drug reactions, or chlamydia.
  • Further Ultrasound may be required for example if there are recurrent UTIs or it does not respond to treatment. An ultrasound taken pre- and post-micturition is helpful in ruling out urinary retention.
  • NB: When a catheter urine sample (CSU) is sent it will almost always be colonised with bacteria (as the catheter equipment is not sterile) so results are often not helpful in making a diagnosis


A UTI is considered complicated when an abnormal renal tract is involved or there is voiding difficulty, when the host is immunodeficient, or if there is a particularly nasty organism involved (eg: Staph. aureus).


If the patient is asymptomatic, treatment is only needed if they are pregnant and expert help should be sought (risk of pre-term labour). Empirical choice is Trimethoprim- 3 day course for simple, 7 days for complicated. Other possibilities include Nitrofurantoin, co-amoxiclav. However, both of these antibiotics are contraindicated at certain stages of pregnancy (trimethoprim is a folate inhibitor so is highly teratogenic in the first trimester, while nitrofurantoin is considered unsafe in the 3rd trimester close to labour due to an association with neonatal jaundice, but evidence suggests it is safe in earlier stages of pregnancy)

If Pyelonephritis is suspected, IV piperacillin/tazobactam (Tazocin) is required.

If the UTI may be due to a catheter, treat if symptomatic, and consider changing the catheter (almost every urine sample from a catheterized patient will have bacteria in it).

Cranberry juice can work in preventing recurrent UTIs in some patients, but the patient needs to drink about 2 glasses a day for a month or more to be effective. It has no therapeutic effect during a UTI (contrary to popular belief).[2]

In Children

If a child has frequent UTIs, they are at risk of Vesicoureteral reflux (VUR), which can damage the kidneys, and should be referred for secondary care.[3]

Risk factors for UTI in children

  • Previous UTI
  • Poor urinary flow
  • Renal structural abnormalities
  • Vesicoureteric reflux (VUR)
  • Constipation

Clinical Features

Note that these are often non-specific, and UTI should be ruled out in the generally unwell child

  • Vomiting
  • Fever
  • Irritability
  • Lethargy
  • Dysuria
  • Frequency/bedwetting

Features of Pyelonephritis

  • Fever
  • Loin pain


  • Urine Dipstick
    • Positive Nitrites
    • Positive Leukocytes
    • Haematuria
    • Proteinuria
  • Microscopy
    • Bacteria
    • White cells (Pyuria)
  • Urine culture
  • Micturating Cystourethrogram
  • DMSA


  • Fluids
  • Encourage micturation
  • Antibiotics
    • Refer to local trust guidelines
    • Well child- often oral trimethoprim
    • Infants/complicated disease- broad spectrum antibiotics


  1. Lane, DR; Takhar, SS (August 2011). "Diagnosis and management of urinary tract infection and pyelonephritis.". Emergency medicine clinics of North America 29 (3): 539–52. doi:10.1016/j.emc.2011.04.001.PMID 21782073.
  2. http://summaries.cochrane.org/CD001321/cranberries-for-preventing-urinary-tract-infections
  3. Bhat, RG; Katy, TA, Place, FC (August 2011). "Pediatric urinary tract infections.". Emergency medicine clinics of North America 29 (3): 637–53. doi:10.1016/j.emc.2011.04.004. PMID 21782079.