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urinary-tract-infections

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Urinary tract infections (UTIs) are caused by pathogenic microorganisms in the urinary tract (the normal urinary tract is sterile above the urethra). UTIs are generally classified by location as infections of the lower urinary tract, involving the bladder and structures below the bladder, or upper urinary tract, involving the kidneys and ureters.

  • UTIs are the second most common (~25% of all infections) )infection in the body. UTIs are common in women, and also make up half of all hospital-acquired infections (often catheter-associated).

Lower Urinary Tract Infections

The sterility of the bladder is maintained by several mechanisms, especially important since the urethra is considered a clean, not a sterile space. The physical barrier of the urethra assists in keeping bacteria away from the bladder, while urine flow helps to carry any bacteria away from the bladder.

Risk Factors for Urinary Tract Infection

  1. Contributory conditions include female gender, diabetes, pregnancy, neurological disorders, gout, and altered states caused by incomplete emptying of the bladder and urinary stasis.
  2. Decreased natural host defenses or immunosuression
  3. Inability or failure to empty the bladder completely
  4. Inflammation or abrasion of the urethra mucosa
  5. Instrumentation of the urinary tract (e.g., catheterization, cytoscopic procedures)
  6. Obstructed urinary flow (e.g., congenital abnormalities, urethra strictures, contracture of the bladder neck, bladder tumors, calculi in the ureters or kidneys, compression of the ureters)

Lower UTIs include bacterial cystitis (inflammation of the urinary bladder), bacterial prostatitis (inflammation of the prostate gland), and bacterial urethritis (inflammation of the urethra).

Pathophysiology

Bacteria enter the urinary tract in three ways: by the transurethral route (ascending infection), through the bloodstream (hematogenous spread), or by means of a fistula from the intestine (direct extension). The most common is transurethral.

  1. In women, the short urethra offers little resistance to the movement of uropathogenic bacteria.
  2. Penile-vaginal intercourse forces the bacteria from the urethra into the bladder.
  3. Bacterial Invasion of the Urinary Tract
  4. Reflux: backward flow of urine from the urethra into the bladder (ureterovesical reflux) or from the bladder to the ureters (vesicoureteral reflux), which may bring bacteria from the anterior portions of the urethra to the bladder.
  5. Bacteriuria: presence of bacterial in the urine established by a clean-catch midstream urine specimen.

Clinical Manifestations

Signs and symptoms of UTI depend on whether the infection involves the lower (bladder) or upper (kidney) urinary tract and whether the infection is acute or chronic.

  1. Uncomplicated Lower UTIs: burning on urination, urinary frequency (more frequent than every 3 hours), urgency, nocturia, incontnience, and suprapubic or pelvic pain. Hematuria and back pain may also be present.
    • In older adults, these symptoms are less common.
  2. Complicated UTIs can range from asymptomatic Bacteriuria to gram-negative sepsis with shock. These are often more difficult to treat and tend to recur.
  3. Catheter-associated UTIs may be asymptomatic. However, any patient with a catheter who suddenly develops signs and symptoms of septic shock should be evaluated for urosepsis (spread of UTI to the bloodstream).

Gerontologic Considerations

  • The incidence of Bacteriuria in older adults differs from that in younger adults. Bacteriuria increases with age and disability, and women are affected more frequently than men.
  • UTI is the most common infection of older adults and increases in prevalence with age. Rates of UTI in men increase due to a higher incidence of bladder outlet obstruction secondary to benign prostatic hyperplasia in men.

Assessment and Diagnostic Findings

  1. Urine Cultures are useful for documenting a UTI and identifying the specific organism present. UTI is diagnosed by bacteria in the urine culture. A colony count greater than 100,000 CFU/mL of urine on a clean-catch midstream or catheterized specimen indicates infection.
  2. Cellular Studies can determine the presence of microscopic hematuria (found in about half of patients with an acute UTI) and pyuria (white blood cells in the urine) that occurs in all patients with UTI. While pyuria is always present, it is not specific as it can also be seen with renal calculi, interstitial nephritis, and renal tuberculosis.
  3. Others:
    • Multiple-test dips tick often includes testing for WBCs, known as the leukocyte esterase test, and nitrite testing.
    • Tests for sexually transmitted infections may be performed because acute urethritis caused by sexually transmitted organisms or acute vaginitis infections, which can mimic the symptoms of UTIs.
    • X-ray images, computed tomography (CT) scan, ultrasonography, and kidney scans are useful diagnostic tools. A CT scan may detect pyelonephritis or abscesses. Ultrasonography and kidney scans are extremely sensitive for detecting obstruction, ascesses, tumors, and cysts.

Medical Management

Management of UTIs typically involves pharmacological therapy and patient education.

  1. Acute Pharmacological Therapy: the ideal medication for treatment of UTI in women is an antibacterial agent that eradicate bacteria from the urinary tract with minimal effects on fecal and vaginal flors, thereby minimizing the incidence of vaginal yeast infections.
    • The most common organism in initial uncomplicated UTIs

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