Bacteria in the urine of a patient with no urinary symptoms are, in almost every setting, something to record rather than treat. Treating it does not reduce symptomatic infection, does not improve outcomes, and reliably produces resistance, Clostridioides difficile and adverse drug effects. It is commonest exactly where it is most often treated — older people, particularly women, patients with indwelling catheters, and patients with diabetes.
There are two established exceptions: pregnancy, where screening and treatment prevent pyelonephritis and preterm birth; and before a urological procedure expected to breach the mucosa and cause bleeding, such as transurethral resection, where treatment is given to cover the procedure rather than to clear the bacteriuria.
The common error is to order the culture in the first place. A urine culture sent without urinary symptoms creates a result that is difficult not to act on, particularly when the patient is unwell for another reason and confusion or a fall is attributed to the urine. In an older person, delirium without urinary symptoms is not by itself a reason to send urine or to start an antibiotic, and doing so most often delays the diagnosis that actually explains the presentation.
A catheter changes nothing about this, except that the bacteriuria is universal after a few days. A cloudy or malodorous bag is not an indication to treat.
- Do not send a urine culture in a patient without urinary symptoms
- Treat asymptomatic bacteriuria only in pregnancy, or before a urological procedure expected to breach the mucosa
- Do not treat on the basis of cloudy or malodorous urine, or of a positive dipstick alone
- In an older person with delirium and no urinary symptoms, look elsewhere before attributing it to the urine
- Expect bacteriuria in every long-term catheterised patient; its presence is not an indication to treat
Why it matters
The antibiotic given for a positive culture in an asymptomatic patient is the commonest avoidable prescription in hospital medicine.
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