06. Urinary Tract Infections

 Resident Editor (2018 Update): Kelly A. Johnson, MD, MPH

Resident Editor (2014):  Benjamin J. Lee, MD

Faculty Editor: Brian Schwartz, MD

BOTTOM LINE

✔ Determine if complicated vs. uncomplicated UTI

✔ Cystitis is the likely diagnosis in women reporting dysuria and no vaginal pain or irritation 

✔ Asymptomatic bacteriuria is common and should not be treated in most patients

Background

  • Most common bacterial infection encountered in outpatient clinics in the US (8.6 million visits in 2007)
  • By age 32, half of women report having experienced a UTI.

Definitions

  • Asymptomatic bacteriuria: Bacteria in urine in the absence of infectious symptoms
  • Lower UTI: Cystitis (bladder infection)
  • Upper UTI: Pyelonephritis and/or renal/perinephric abscess
  • Uncomplicated UTI:  UTI in an otherwise healthy, non-pregnant woman
  • Complicated UTI: Includes UTI in men, pregnant woman, or patients with abnormal GU anatomy (obstruction, stricture, stone, indwelling catheters) or neurogenic bladder; also includes ESRD, transplant recipients, and immunosuppressed patients 
  • UTI risk factors: Female gender (shorter urethra), sexual intercourse, spermicide use (alters vaginal flora), pregnancy, history of UTIs, diabetes, indwelling catheter, recent urologic instrumentation, BPH

Signs and Symptoms

  • Lower UTI: Dysuria, increased urinary frequency/urgency, suprapubic pain
  • Upper UTI: Symptoms of lower UTI (may or may not be present), fever, flank pain, nausea, vomiting

Differential Diagnosis

  • Urethritis, vaginitis, pelvic inflammatory disease, interstitial cystitis/bladder pain syndrome, prostatitis, nephrolithiasis

Evaluation

  • History: Probability of cystitis is >90% in women reporting dysuria and no vaginal pain or irritation.
  • Exam: Assess for suprapubic and CVA tenderness; vaginal/pelvic exam may be warranted if diagnosis unclear.
  • Work-up: Women with classic symptoms of an uncomplicated UTI and no evidence of an alternative diagnosis may be treated empirically without testing. UA and urine culture are recommended in treatment failure, recurrent UTIs, all complicated UTIs, and/or when the history alone is not diagnostic.
    • Urinalysis: Presence of pyuria (>10 WBC/hpf), nitrites (Enterobacteriaceae convert urinary nitrate to nitrite), and leukocyte esterase (released from granulocytic WBC) are suggestive of UTI. WBC casts suggest upper UTI.
    • Urine culture: Midstream void considered positive when ≥105 CFU/mL present, though some data show correlation with bladder culture if >102 CFU/mL (E. coli, Klebsiella, S. saprophyticus) detected, and symptomatic patients should still be treated. Urine culture provides speciation and antibiotic susceptibilities.

Microbiology

  • Most uncomplicated UTI are caused by E.coli (>90%). Other causative organisms include Proteus mirabilis, Klebsiella pneumonia, and Staphlycoccus saprophyticus.
  • While pathogenic in some settings, Lactobacilli, enterococcus, Group B strep, coagulase-negative Staph (other than S. saprophyticus), and candida are often contaminants.

Treatment

  • Consider the diagnosis of pyelonephritis before initiating treatment for acute cystitis.
  • Also consider any complicating factors such as underlying medical conditions, abnormal anatomy, and adherence to medications.

Diagnosis

Empiric Treatment

Asymptomatic bacteriuria
  • Treatment only recommended in pregnant women and prior to invasive urologic procedures
  • Common in many populations where treatment is not recommended, including: diabetic women (~25%), elderly patients in long-term care facilities, spinal cord injuries
  • Pyuria is also not an indication for treatment

Uncomplicated UTI
  • Nitrofurantoin 100 mg BID x 5 days (contraindicated when CrCl <60 mL/min)

or

  • TMP/SMX 1 DS tab BID x 3 days (avoid when local resistance > 20%)

or

  • Fosfomycin 3 gm PO x 1

Complicated UTI
  • Ciprofloxacin 500 mg BID or levofloxacin 750 mg daily x 7 days

or

  • TMP/SMX 1 DS tab BID x 7 days

In pregnant women (lower UTI)

  • Amoxicillin/clavulanate 875 mg BID x 7 days

or

  • Cephalexin 500 mg QID x 7 days

or

  • Nitrofurantoin 100 mg BID x 7 days (avoid after 37 weeks gestation or during breastfeeding, due to risk of hemolytic anemia in newborns)

Uncomplicated pyelonephritis (mild systemic symptoms, able to maintain adequate hydration and PO intake; not pregnant, no stone or obstruction)
  • Ciprofloxacin 500 mg BID or levofloxacin 750 mg daily x 7 days (avoid when local resistance rates >10%; also consider adding a one-time dose of an IV antimicrobial such as 1g ceftriaxone)

or

  • TMP-SMX 1 DS tablet BID x 10-14 days (if pathogen known to be susceptible; otherwise give an initial dose of IV medication as above)

Recurrent cystitis (symptoms persisting or recurring within 2 weeks of treatment or 3+ episodes within 1 year)

Obtain urine culture and begin treatment with fluoroquinolone while awaiting culture data

Screening and Prevention

  • Screening and treatment for asymptomatic bacteriuria only recommended in pregnant women and in patients prior to urologic instrumentation.  (Also consider treatment in neutropenic patients.)
  • Advanced age, institutionalization, diabetes, and presence of an indwelling catheter are NOT indications for screening or treatment of asymptomatic bacteriuria.
  • Consider post-coital antibiotic prophylaxis in women with multiple UTIs (>3) per year if infection is strongly temporally associated with sexual intercourse.
  • Topical intravaginal estrogen therapy may be considered in postmenopausal women with recurrent UTIs.
  • Prophylactic antibiotics for 6-12 months may be considered in women with >3 UTIs per year if above interventions fail.
  • Studies have inconsistently shown a benefit of post-coital voiding, probiotics, or cranberry juice to reduce the incidence of UTIs, although these strategies may still be recommended given the low risk of the interventions.

References

Flores-Mireles A, Walker JN, Caparon M, et al. Urinry tract infections: epidemiology, mechanisms of infection, and treatment options. Nat Rev Microbiol 2015; 13(5):269-284.

Gupta K, Grigoryan L, Trautner B. In the clinic. Urinary tract infection. Ann Intern Med 2017; 167(7):ITC49-ITC64.

Gupta K, Hooton TM, Naber KG, et al. International clinical practice guidelines for the treatment of acute uncomplicated cystitis and pyelonephritis in women: A 2010 update by the Infectious Diseases Society of America and the European Society for Microbiology and Infectious Diseases. Clin Infect Dis 2011; 52:e103-120.

Hooton TM. Clinical practice. Uncomplicated urinary tract infection. N Engl J Med 2012; 366:1028-1037.

Hooton TM, Roberts PL, Cox ME, Stapleton AE. Voided midstream urine culture and acute cystitis in premenopausal women. N Engl J Med. 2013; 369(20):1883-91.

Mody L, Juthani-Mehta M. Urinary tract infections in older women: a clinical review. JAMA 2014; 311(8):844-54.