Diagnosing Lower Urinary Tract Infections

Few shifts go by without ordering at least one urinalysis. While they are ubiquitously used, urine testing is often unneeded and frequently misleading. How often do you feel frustrated about a urine sample that takes too long to obtain? You may not need the sample in the first place. To understand why, we need to go back to the basics and think carefully about the indications for obtaining a urinalysis. Let’s look at three young female patients with differing symptom severities. For simplicity, we will focus only on the patients with suspected lower urinary tract infection (UTI). Patients with flank pain (which would suggest pyelonephritis) as well as patients meeting two or more SIRS criteria (which would suggest sepsis) comprise a higher risk group. As a result, obtaining a urinalysis in these patients is almost always prudent.

A UTI is defined as a combination of UTI symptoms and a positive urine culture for pathogenic bacteria.1 In the absence of lower UTI symptoms like dysuria, urgency, or frequency, by definition, a patient does not have a UTI and therefore does not need treatment with antibiotics. Even without any UTI symptoms, a young female patient has around five percent chance of having bacteriuria.2 In this population, urine testing can only be misleading and result in unnecessary antibiotic prescription. In their recent 2023 guidelines, the European Association of Urology gives a strong recommendation against urine testing in most asymptomatic patient populations, including women with well controlled diabetes, post-menopausal woman, nursing home patients and even patients with renal transplants.3 The only two exceptions where a urinalysis is indicated despite having no UTI symptoms are pregnant patients and patients about to undergo urological procedures.3 Avoiding antibiotics in asymptomatic patients is not just about antibiotic stewardship. Antibiotics can cause harm and make patients more susceptible to true UTIs by altering their urinary tract microbiome. In a large, randomized controlled trial, when patients with asymptomatic bacteriuria were treated with antibiotics, 47 percent developed symptomatic UTIs within a year compared to only 13 percent of untreated patients.4 Therefore, the best course of action for patients without clear UTI symptoms is not to order a urinalysis in the first place.

What about the young female patient with dysuria and urinary frequency who is telling you that she thinks she has a UTI? As long as she is not having vaginal discomfort or discharge (which would point to sexually transmitted infections), this patient has about 90 percent chance of having a UTI.5 Even with a negative leukocyte esterase and nitrite, this patient still has a 71 percent chance of a UTI, so if you withhold treatment based on a negative urinalysis, you would be under-treating nearly three quarters of these patients.5 Therefore, the best course of action for highly symptomatic patients without vaginal symptoms is empiric treatment with antibiotics without ordering a urinalysis. The most recent European Association of Urology guidelines again support this practice, giving a “strong” recommendation for diagnosing uncomplicated UTIs based on UTI symptoms alone in the absence of vaginal symptoms.3 A narrow spectrum antibiotic such as a single dose of fosfomycin in the emergency department is the way to go and has the added convenience of being a one and done solution that doesn’t require the patient to fill a prescription.

Patients who present with an isolated single UTI symptom like urinary frequency or urgency have about 50 percent chance of having a UTI.5 A urinalysis can be very helpful in this patient population to guide treatment decisions. A negative leukocyte esterase and nitrite brings the UTI probability down to about 20 percent, and a positive nitrite brings it up to almost 90 percent.6 Therefore, with a negative leukocyte esterase and a negative nitrite, you can withhold treatment, while a positive nitrite should trigger antibiotic administration regardless of the leukocyte esterase result. For the ambiguous cases with a positive leukocyte esterase and a negative nitrite, a wait and see approach can be utilized, as up to 43 percent of proven UTI patients have symptom resolution within three days with NSAID treatment alone.7 While progression to pyelonephritis is uncommon with NSAID treatment alone at around 5 percent, antibiotic treatment lowers pyelonephritis risk to less than 0.2 percent, so the risks and benefits of withholding antibiotics must be weighed carefully for the individual patient, and strict return precautions should be utilized in case the patient’s symptoms persist beyond three days or if they develop a fever.7

The ubiquitously ordered urinalysis is, like any other test, only useful if used in the right patient population. For young female patients without any classic symptoms of a UTI, there is no need to order a urinalysis. For those with multiple UTI symptoms, again, there is no need to order a urinalysis and empiric antibiotics is appropriate. Urinalysis can be helpful in young female patients with single isolated symptoms of UTI. Next time, before you order a urinalysis, think carefully about whether you are ordering it for the right patient.

Dr. Aydemir is a PGY-3 emergency medicine resident at Western Michigan University Homer Stryker M.D. School of Medicine.

Dr. Overton is chair of the department of emergency medicine at Western Michigan University Homer Stryker M.D. School of Medicine.

  1. Schmiemann G, Kniehl E, Gebhardt K, Matejczyk MM, Hummers-Pradier E. The Diagnosis of Urinary Tract Infection: A Systematic Review. Dtsch Arztebl Int. 2010;107(21):361. doi:10.3238/ARZTEBL.2010.0361
  2. Hooton TM, Scholes D, Stapleton AE, et al. A Prospective Study of Asymptomatic Bacteriuria in Sexually Active Young Women. New England Journal of Medicine. 2000;343(14):992-997. doi:10.1056/NEJM200010053431402
  3. Bonkat G, Bartoletti R, Bruyere F, et al. EAU Guidelines on Urological Infections. Published online 2023. Accessed March 17, 2024. https://uroweb.org/guidelines/urological-infections
  4. Cai T, Mazzoli S, Mondaini N, et al. The Role of Asymptomatic Bacteriuria in Young Women With Recurrent Urinary Tract Infections: To Treat or Not to Treat? Clinical Infectious Diseases. 2012;55(6):771-777. doi:10.1093/CID/CIS534
  5. Chu CM, Lowder JL. Diagnosis and treatment of urinary tract infections across age groups. Am J Obstet Gynecol. 2018;219(1):40-51. doi:10.1016/J.AJOG.2017.12.231
  6. Medina-Bombardó D, Jover-Palmer A. Does clinical examination aid in the diagnosis of urinary tract infections in women? A systematic review and meta-analysis. BMC Fam Pract. 2011;12:111. doi:10.1186/1471-2296-12-111
  7. Ong Lopez AMC, Tan CJL, Yabon AS, Masbang AN. Symptomatic treatment (using NSAIDS) versus antibiotics in uncomplicated lower urinary tract infection: a meta-analysis and systematic review of randomized controlled trials. BMC Infect Dis. 2021;21(1). doi:10.1186/S12879-021-06323-0