The Curbsiders 'Hot Takes'

What I Didn't Know About Urine Blew My Mind

The Curbsiders

Disclosures

October 05, 2020

This transcript has been edited for clarity.

Matthew F. Watto, MD: Welcome back to the Curbsiders. I'm Dr Matthew Frank Watto, here with my glorious friend Dr Paul Nelson Williams. So, Paul, what are we doing on today's video?

Paul N. Williams, MD: Our expert for this episode was Dr Boghuma Titanji, who talked to us about the management of urinary tract infection (UTI). It was a great interview that covered a lot of territory but also some of the fundamentals too, so we had a fantastic conversation.

Watto: You are going to give the first pearl, but before you do: What exactly is a UTI, because I don't think it's as easy to define as people may think.

Williams: You asked that question during the interview, and I immediately broke into a cold sweat, because I realized that if someone asked me that, I would not be able to define it well. But luckily, I'm not the expert. Dr Titanji defines it very simply as a significant bacteriuria with signs that localize to the urinary tract.

She subdivides further into simple and complicated UTI, which we know, but her definitions and framework made it much more understandable to me. A simple UTI is an infection at the level of the bladder or below, and complicated UTIs are infections that affect the urinary tract above the bladder — the kidneys and ureters, that territory. I thought that very basic framework was helpful.

Treatment for a simple UTI is fairly straightforward, which is reassuring to someone like me who overthinks things. There aren't a whole lot of options. Her choices are trimethoprim-sulfamethoxazole (TMP-SMX), fosfomycin, and nitrofurantoin. Those are the first-line agents; there's not a whole lot to mess around with.

Watto: That's exactly right. I want to point out one more thing. We wouldn't be using those three antibiotics for complicated UTI (anyone with systemic symptoms — rigors, fevers, upper urinary tract symptoms). When making treatment decisions for complicated UTI, what we should be asking is, how sick is the patient?

Speaking of sick patients, a pearl that can't be repeated enough is this: In uncomplicated UTI, when the patient has bacteremia (and commonly, it's gram-negative bacteremia with some sort of Enterobacter spp, such as Klebsiella or Escherichia coli), we talked about treating them for 7 days and they rapidly get better. Dr Titanji mentioned that certain oral agents achieve high blood levels, and there's really only two that we commonly use for UTIs: the fluoroquinolones and TMP-SMX. When patients have a bacteremia and she's stepping down from intravenous (IV) therapy, she usually tries to put someone on TMP-SMX or a fluoroquinolone because of that high blood level. I hadn't thought about antibiotics that way. We can link to a blog post by Dr Paul Sax where he lists which antibiotics achieve high blood levels and which ones don't. The beta-lactams — the penicillin agents and cephalosporins — do not achieve high blood levels. That's important for our audience to know.

So, Paul, bring us home. What else?

Williams: She scolded me and broke my heart on point-of-care urinalysis (POC UA), something I don't think I was previously aware of. She made a couple of really good points about using urinalysis in the office. First, it's a useful tool to rule out UTI. If you don't see any evidence of leukocyte esterase on the POC UA, the odds of it being a UTI are incredibly low, White cells release leukocyte esterase, so it's present if there are white cells — end of story — and if it's not present, it makes it much harder for this to be a UTI.

The other point, which made me feel especially dumb (which is my baseline in any case), is that in order to detect nitrites in the UA, you need a dwell time of urine in the bladder of about 4 hours. So ideally you are doing this first catch, in the morning, with nondilute urine. So when these patients come in the afternoon and they've already gone to the bathroom four times that day and had the Big Gulp soda, the chances of you actually catching a positive nitrite test on their urine are pretty low, even if there are bacteria that would normally manufacture those things. It's not a specific nuance about urinalysis that I knew before, and one that kind of blew my mind.

Watto: Yeah, I was sufficiently shaken by that one. I had no idea. So if this all sounds interesting to you — and it should, this was a fantastic episode — you can click on the link in the transcript to hear the full podcast episode, and you can also visit Curbsiders.com if you want to sign up for our mailing list to get our weekly show notes and see which episode is coming out that week.

Click to hear the full episode, #231: U Talkin' UTIs Re: Me?, or find the Curbsiders podcasts on iTunes.

The Curbsiders is a national network of students, residents, and clinician educators from across the country, representing 15 different institutions. They "curbside" experts to deconstruct various topics in the world of medicine to provide listeners with clinical pearls, practice-changing knowledge, and bad puns. Learn more about their contributors and follow them on Twitter.

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