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Clinical Opal #20 - An abnormal urine culture

21 November 2022 - Dr Simon Morgan

You click on the MSU result for Una Chong, a 78 year old woman, and see the following:

Specimen: Mid-stream urine

Microscopy

Leucocytes 10-100 per hpf
Squamous cells <10 per hpf
Red blood cells <10 per hpf

Culture

Pure growth E.coli  >105/mL

You review Una’s notes and see that she had been in for a 75+ year health assessment the previous week. Dipstick urine testing was positive for leucocytes and a formal MSU was requested.

You call Una and confirm that she is completely free from urinary symptoms.

What is the diagnosis and what management should be instituted?



Una has asymptomatic bacteriuria (AB). AB is a common clinical finding, with approximately 15% of older women and up to 50% of RACF residents having the condition.


However, in most cases AB does not lead to UTIs.1 A 2015 Cochrane review on antibiotic treatment for AB found that there was no clinical benefit for antibiotic treatment.2 And a recent systematic review looking at the effectiveness, harms, and adverse events associated with antibiotic treatment for RACF residents with AB found although antibiotic treatment was associated with bacteriological cure, it was also associated with significantly more adverse effects.3

It follows that screening patients for AB is inappropriate in most cases, as with Una. Australian guidelines state that screening for AB is not recommended, except for pregnant women and patients undergoing elective urological procedures.4 They go on to say that requesting a urine culture without a clear indication, or failing to correctly interpret the culture result in the clinical context, significantly contributes to antibiotic misuse.

Additionally, the RCPA recommends as part of the Choosing Wisely Australia initiative do not perform surveillance urine cultures or treat bacteriuria in elderly patients in the absence of symptoms or signs of infection.

Una's case is an example of non-rational testing and illustrates the potential harms associated with inappropriate testing - further investigations, unnecessary treatment and risk of adverse effects.


References

  1. Colgan R, Jaffe GA, Nicolle LE. Asymptomatic Bacteriuria. Am Fam Physician. 2020 Jul 15;102(2):99-104.
  2. Zalmanovici Trestioreanu A, Lador A, Sauerbrun-Cutler M, Leibovici L. Antibiotics for asymptomatic bacteriuria. Cochrane Database of Systematic Reviews 2015, Issue 4.
  3. Krzyzaniak N, Forbes C, Clark J, Scott AM, Mar CD, Bakhit M. Antibiotics versus no treatment for asymptomatic bacteriuria in residents of aged care facilities: a systematic review and meta-analysis. Br J Gen Pract. 2022 May 6;72(722):e649–58. 
  4. Therapeutic Guidelines, Antibiotic.
Dr Simon Morgan
Dr Simon Morgan

Simon is a GP based in Newcastle, NSW, and a senior medical educator with Medcast.  He also has medical education roles with the RACGP and GPSA.

Over the past three decades, Simon has worked in clinical and educational roles in NSW and the NT, as well as in the Republic of Ireland. He has published over 75 peer reviewed journal articles, and in 2018 received the RACGP Corliss award for his contribution to medical education.

Simon is passionate about high quality education and training. He has particular interests in GP supervisor professional development and the rational use of tests and medicines. He is a proud member of Doctors for the Environment. He spends his spare time drinking craft beer and pretending that he is a musician in the Euthymics, an all-GP band.

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