In this review, the authors debunk a number of myths about UTIs and the utility of urinalysis. As they conclude:
Asymptomatic bacteriuria is common in all age groups and is frequently over-treated. A UTI diagnosis should be based on a combination of clinical symptoms with supportive laboratory information.
Myths and Truths
|1||Cloudy, smelly urine = UTI||Neither sensitive nor specific, and largely influenced by hydration status and urea concentration|
|2||There are bacteria! = UTI||Samples may be contaminated and patients may have asymptomatic bacteriuria. Diagnosis of UTI requires symptoms (regardless of bacteria count)|
|3||A high bacterial count is a positive result, despite high epithelial cell count and = UTI||This sample is contaminated and needs recollection|
|4||The urinalysis is positive for leucs! = UTI, requiring culture and ABx||Leucocyte esterase on urinalysis is sensitive and specific for pyuria, but does not diagnose UTI in the absence of symptoms.
Symptoms with a negative leucocyte esterase may still prompt cultures, but also consider urethritis, vaginitis, or STIs.
|5||There is a high white cell count! = UTI||Oliguria, dehydration, haematuria, acute renal failure, STIs, or noninfectious cystitis (eg due to a catheter) can all cause pyuria in the absence of UTI.
Conversely, patients with neutropaenia may have a low urine WCC in the presence of UTI.
|6||Urinary nitrites = UTI||The presence of nitrites is sensitive for bacteriuria, but that does not mean UTI (see #2).
Positive nitrites and leucocyte esterase has only moderate sensitivity for UTI in elderly patients and need to be correlated to symptoms.
A negative nitrite and leucocyte esterase effectively rules out UTI in the large proportion of patients.
|7||Bacteria in a catheterised urine sample = UTI||Nearly all catheters are colonised within 2 weeks with 2-5 strains of bacteria. Ewww.|
|8||Ok, then, bacteriuria may not be UTI now, but will lead to UTI later...||Asymptomatic bacteriuria has not been associated with long-term negative outcomes such as pyelonephritis, sepsis, renal failure, or hypertension. In fact, bacteriuria in young women may actually protect against more pathogenic infections.
Use of antibiotics for bacteriuria selects ongoing colonisation with resistant strains.
|9||Falls and altered mental state in the elderly = UTI||These presentations are multifactorial. Evidence of systemic infection or urinary symptoms are required to diagnose UTI. The presence of bacteriuria or pyuria alone do not indicate UTI as a source.|
|10||Candida in the urine = UTI||Candiduria is common in catheterised patients. As always, treatment should occur only where there are signs and symptoms of infection and no alternative source of infection.|
The Bottom Line
The diagnosis of UTI is clinical and based on the presence of symptoms. The results of urinalysis must be considered in context.