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    Urinary Tract Infection (Adult) – Diagnosis

    Cardinal Presentations / Presenting Problems, Infections, Urological

    Last Updated Dec 11, 2019
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    Context

    • Common ED presentation.
    • 10X more frequent in women.
    • 1 in 5 women will have UTI in lifetime.
    • Usually uncomplicated, treated with oral antibiotics.

    Deifintions, Classification, Etiology

    Definitions:

    • Pyuria: WBC in urine.
    • Bacteriuria: Bacteria in the urine, >10^5 colony forming units (CFU)/mL with culture.

    Classification:

    • Uncomplicated UTI/Cystitis:
      • Lower tract infection
        • Bladder (cystitis) and urethra (urethritis)
        • Usually healthy non-pregnant women with no anatomical abnormalities
    • Complicated UTI:
      • Upper tract infection
        • Renal Parenchyma + collecting system (pyelonephritis)
      • *Considered complicated if [3]:
        • Male
        • Pregnancy
        • Urolithiasis
        • Structural Abnormalities
        • Catheters/Stents
        • Antibiotic Failure
        • Hospital-associated UTI
        • Immunocompromised
        • Malignancy

    Etiology:

    • Urine should be sterile from glomerulus to external sphincter in male and bladder neck in females.
    • Sterility is due to forward flow, urine acidity, immune system, mucosal barrier.
    • Infections are caused by problems in anatomy, structure and function. Also instrumentation.
      • Anatomy:
        • Incompetence in ureterovesical valve –>  vesicoureteral reflux (VUR)
          • 1/3 children under 24 months with febrile UTI
          • Neurogenic bladder
          • Urologic Surgery
        • Congenital urethral valves
        • Bladder diverticulum
      • Structure:
        • Calculi
        • Intrinsic or extrinsic mass effect
          • Example: Men – BPH, urethral stricture
          • Example: Women – Fibroids, pregnant, uterine prolapse or cystocele
        • Function:
          • Dysfunction in bladder emptying
            • Neurogenic bladder
            • Drugs
              • Anticholinergics
              • Antihistamines
              • Antipsychotics
              • Antidepressants
              • Antiparkinsonian
              • Sympathomimetics
              • Muscle Relaxants
            • Instrumentation:
              • Most common cause of nosocomial UTI is Foley catheters
            • Lifestyle:
              • Sexual intercourse, toilet hygiene
                • Introduces bacteria into a woman’s urinary tract
                  • Evidence for cranberry as a UTI prophylactic

    Pathophysiology of UTI. (Source: Dubbs and Sommerkamp, 2019)

     

    Microorganisms:

    • Uncomplicated/Complicated: E.Coli (greater than 80%), Staphyloccus Saprophyticus (15%).  Can include other gram negatives (Klebsiella, Proteus) and gram positive (enterococcus, GBS).
    • Considerations:
      • Complicated UTI (eg. catheter associated or elderly men) can be polymicrobial.
      • Pseudomonas, Enterococcus faecium, ESBL result in complicated infections.
      • Fluoroquinolone resistance increasing.

     

    Diagnostic Process

    • Stable vs Unstable Patient
    • UTI vs UTI Mimic (see differential below)
    • Simple vs Complicated UTI

    History:

    • Cystitis: Can include dysuria, urinary frequency, urgency, hematuria
    • Pyelonephritis: Can include progression of cystitis to fever, nausea/vomiting, flank pain
    • *Include questions to cover differential (see below). Examples:
      • Abnormal vaginal discharge or bleeding? Dyspareunia?
      • Unprotected sexual intercourse?
      • Last Menstrual Period
    • Note: Atypical presentations are not uncommon in the elderly

    Physical Exam:

    • Suprapubic tenderness on abdominal exam
    • CVA tenderness common in pyelonephritis
    • Vital sign abnormalities in complicated UTI (eg. sepsis)
    • *Include exam to cover a differential. Examples:
      • Vaginal/Cervical exam
      • Testicular Exam
      • Abdominal Ultrasound to assess for Abdominal Aortic Aneurysm [see video]

    *Differential Diagnosis (UTI mimics) [3]:

    • Bacterial Vaginosis
    • Sexually transmitted disease (STD)
    • Pelvic inflammatory disease (PID)
    • Epididymitis/orchitis
    • Testicular/ovarian torsion
    • Ectopic Pregnancy
    • Cholecystitis
    • Urolithiasis
    • Renal abscess, infarction or thromboembolism
    • Appendicitis
    • Abdominal Aortic Aneurysm

    Urine Dipstick:

    • Most commonly used method to diagnose UTI
    • Similar sensitivity and specificity to microscopy
      • Leukocyte Esterase – marker of pyuria
        • Diagnosis: Sensitivity 75 – 96%, Specificity 94-98%
        • False Negative with antibiotic therapy, glycosuria, proteinuria
      • Nitrite – marker of bacteria that convert nitrate to nitrite
        • Diagnosis: Sensitivity 35-85%, Specificity 95%
        • False Negative with non-nitrate-reducing bacteria (S. saprophyticus, Pseudomonas, enterococci)
      • Leukocyte Esterase and Nitrite:
        • Diagnosis: Sensitivity 75-90%, Specificity ~ 100%
        • “What if clinically suggestive of UTI, but both Leukocyte Esterase and Nitrite negative?”
          • May still require antibiotics as there are chances for false negatives.
          • Self diagnosis has positive likelihood ratio of 4 (absence of vaginitis symptoms, likelihood ratio of 24)
          • Clinical gestalt is important.
        • “What if asymptomatic but positive leukocyte esterase and/or nitrite?”
          • May not require antibiotics. Patient factors (eg. Pregnancy, Immunocomprimised) are important in decision making.  See UTI Special Considerations section on Asymptomatic Bacteriuria for more details.

    Microscopy:

    • Optional but perform in recurrent UTI
    • Can determine if sample contaminated
    • > 10 WBC/mm^3 (non-centrifuged) or > 2-5 WBC/mm^3 (centrifuged) indicative of UTI
    • >= 15 bacteria per high power field indicative of UTI
    • WBC casts suggestive of Pyelonephritis
    • Hematuria helpful in UTI diagnosis
    • Note: UTI diagnosis can be made with microscopic bacteriuria and pyuria (+/- hematuria)

    Urine culture:

    • Not done in cases of uncomplicated UTI (clinical diagnosis)
    • Perform in complicated UTI or recent antibiotic use
    • Positive when:
      • Suprapubic sample: any bacteria
      • Urethral Catheter: >10^2 cfu/mL, single uropathogen, clinical symptoms
      • Non-catheter: >10^5 cfu/mL
        • >10^2 cfu/mL if known uropathogen in patient with clinical symptoms

    Blood Cultures:

    • Do not usually alter management
    • Usually concordant with urine culture
    • Perform in cases of sepsis or septic shock. Can consider in elderly, immunocompromised, urinary tract obstruction

    Imaging:

    • Not necessary in simple cystitis
    • Use if concerned for mimics
    • Consider for complicated UTI
    • No role for plain radiographs
      • KUB sensitivity 45-59 %/specificity ~77% (for renal pathology)
    • Ultrasound
      • Ideal in cases involving pelvic structures
      • Can visualize hydronephrosis
      • CT is frequently used in complicated UTI
        • Most sensitive test for renal pathology
          • If concerned about severe disease, or UTI mimics, CT is warranted
          • IV contrast if concerned for embolus or thrombus

    Clinical scenario

    STD vs UTI

    • Can be difficult to distinguish because of overlap in symptoms (eg. dysuria)
      • STD symptoms more gradual in onset and includes vaginal discharge/bleeding, pruritus, dyspareunia. Not typical to have change in urinary frequency/urgency.
      • Assess for STD risk factors including a sexual history
      • Perform vaginal/cervical exam and swabs
      • Can consider treatment of both concurrently
      • Tomas et al. performed an observational cohort study concluding the following:
        • UTI’s are over diagnosed and STD’s are underdiagnosed in the emergency department
        • STD’s can have abnormalities in urinalysis – positive leukocyte esterase or pyuria (defined as more than 5 WBC per HPF)
        • Positive urinalysis does not equal UTI. Can have false positives (eg. STD, asymptomatic bacteruria)
      • Recommendation:
        • STD’s are a common UTI mimic. Take an appropriate history and physical exam/investigations.  Consider treating both.  Use clinical gestalt.  Have appropriate follow-up.

    Quality Of Evidence?

    Justification

    The above summary is taken from recent literature reviews on emergency department diagnosis and management of UTI’s.

    High

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