Asymptomatic Bacteriuria: Are Emergency Physicians Part of the Problem or Part of the Solution?
Bobby Redwood, MD, MPH
A 72 year-old female presents from your local nursing home with altered mental status. She's comfortable and conversive with normal vital signs and no pain on exam, but thinks its 1956 and calls you and all your staff, "Ralphie". You're handed seven pages of medication administration records without any past medical history or history of present illness. You call for additional information, but they just had a shift change and no one at the facility is able to tell you what happened. After a head CT, chest Xray, EKG and rainbow labs, the only abnormal finding is a urinalysis with bacteria, pyuria, nitrites, and leukocyte esterase. Your nurse reports the urine was dark and foul smelling.
Alright Ralphie, this is where the rubber hits the road...what do you do?
If you are like me, you are probably tempted to do a quick fist pump because you found something to treat, order a gram of ceftriaxone, admit the patient to the medicine floor and get on with your shift. Depending on where you work, this method of management may earn you a talking to from the nursing home director or your infectious disease department. You may find yourself being shamed for practicing sloppy medicine and contributing to antibiotic resistance. Deep down, you have doubts that the bacteriuria caused the altered level of consciousness, but you were practicing in the real world, with little clinical background on the patient, and needed to make a game day decision...what's an emergency physician to do?
Asymptomatic bacteriuria (also known as an asymptomatic urinary infection) is defined as an isolation of bacteria in an appropriately collected urine sample without signs or symptoms to a urinary infection (sorry folks, altered mental status is not a sign of a UTI). The prevalence of asymptomatic bacteriuria is between 5-7% in healthy adult women, but skyrockets to 10-50% in the nursing home population and nearly 100% in patients with chronic indwelling catheters.
There was a time when all asymptomatic bacteriuria was treated as though it were a clinical UTI. The practice started because pregnant women with asymptomatic bacteriuria frequently went on to develop pyelonephritis. When the asymptomatic bacteriuria was treated, no pyelonephritis ensued. Clinicians of that era hypothesized that asymptomatic bacteriuria was consistently harmful in all populations and thus warranted antimicrobial treatment. This turns out not to be true; outside of pregnancy and patients undergoing urologic procedures, treating asymptomatic bacteriuria gives your patient all the risks of antimicrobial therapy with none of the benefit. Adding insult to injury, the practice of treating asymptomatic bacteriuria contributes significantly to the public health threat of antimicrobial resistance (especially in nursing home populations). Ready for a shock? A 2014 report from the CDC estimates that 39% of antibiotics prescribed for "UTI" were not necessary. The data is there, but so is the dogma...so I ask you again...what's an emergency physician to do?
By arming ourselves with information, we can develop an approach to asymptomatic bacteriuria that is reasonable, defensible, and protects the public health without jeopardizing the health of the individual patient. Here are some common myths about UTIs and asymptomatic bacteriuria:
- Smelly pee = UTI. Foul smelling urine or change in urine appearance does not correlate with infection. It is usually related to hydration status.
- WBCs = UTI. Pyuria is inflammation within the genitourinary tract and is measured as WBCs in the urine. It is a common accompaniment of asymptomatic bacteriuria and should not influence decisions about antimicrobial therapy.
- Leukocyte esterase and/or nitrites = UTI. Not so fast, leukocyte esterase suggests pyuria and nitrites suggest bacteria--either of these could be present in asymptomatic bacteriuria, so clinical context (i.e. symptoms) really matters.
- Positive culture always means UTI. A good specimen has fewer than five epithelial cells per low-power field on urinalysis. A "positive" culture is meaningless if the sample was contaminated.
- UTI is a common cause of altered mental status in the elderly. Actually it is an uncommon cause and this type of anchoring bias can work against us in terms of uncovering the true cause of our patient's altered mental status. Before you think UTI, think of more common (and also more subtle) etiologies like medication reactions, sundowning, dehydration or sensory impairment.
Let's get back to our patient; she's altered, her urinalysis sure looks "positive", and she lives in a nursing home that is likely covered from floor to ceiling in a thin film of gram positive rods, so I ask you yet again...what's an emergency physician to do?
- First, check prior records to see if her urinalysis always appears "positive", you may discover a trend of asymptomatic bacteriuria.
- Second, recall that UTI is an actually an uncommon cause of delirium and the chances that your patient has occult bacteremia from a urinary source are low.
- Third, do not administer antibiotics and let your admitting physician know that you are consciously resisting the urge to treat the "UTI" in favor of uncovering the more likely alternate cause of her altered mental status.
- Lastly, check your inbox to read emails of praise from your infectious disease and long term care colleagues--you, my friend, are a cautious physician and a noble steward of antibiotics!
In summary, inappropriate treatment of asymptomatic bacteriuria is a big problem. Some of us are part of the problem, others are part of the solution. If 39% of the antibiotics prescribed for UTIs are unneccesary, we have some work to do in terms of educating our workforce and our patients about asymptomatic bacteriuria. If this is a topic that is relevant in your ED, think about sitting down with your inpatient team and hammering out a protocol to ensure a uniform approach towards asymptomatic bacteriuria.
Want to learn more? Check out this 2016 article on the topic by Wisconsin emergency physician Jeff Pothof!
Bottom line: "Elderly patients with acute mental status changes accompanied by bacteriuria and pyuria, without clinical instability or other signs or symptoms of UTI, can reasonably be observed for resolution of confusion for 24–48 h without antibiotics, while searching for other causes of confusion" [J Emerg Med. 2016;51(1):25-30].