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Infectious Diseases - Urinary Tract Infections - Fast Facts | NEJM Resident 360

Urinary tract infections (UTIs) are frequently encountered in the outpatient and inpatient settings. UTIs can range in severity and organs involved. With increasing indwelling urinary catheter use, catheter-associated UTIs (CAUTIs) have become a quality and safety measure that can affect reimbursement rates. In this section, we will cover the diagnosis and treatment of the following UTI-associated conditions:

• Cystitis

• Pyelonephritis

• Prostatitis

• Catheter-Associated UTI (CAUTI)

Cystitis

Acute cystitis is the most common presentation of UTI. Cystitis is more frequent in women and is associated with high recurrence rates. Healthy nonpregnant women with normal urinary tract anatomy and no recent instrumentation (e.g., catheters, stents, endoscopes) are considered to have uncomplicated disease. Uncomplicated cystitis rarely progresses to severe disease or pyelonephritis, even if untreated.

Diagnosis

Symptoms of cystitis include:

• dysuria

• frequency

• urgency

• suprapubic pain

• hematuria

Fever is more suggestive of pyelonephritis. Urethritis and vaginitis can mimic cystitis with symptoms of dysuria, but urethritis or vaginitis are not usually associated with other UTI symptoms.

Urinalysis (via dipstick)

Look for presence of:

• leukocyte esterase: enzyme released by white blood cells (WBCs)

• nitrites: poor sensitivity alone because only some bacteria reduce nitrates to nitrites

• pyuria: ≥10 WBCs/mm³ or ≥3 WBCs/high-power field of unspun urine; absence of pyuria has good negative predictive value

Urine culture

Urine culture confirms the presence of bacteriuria, provides antimicrobial susceptibility, and is indicated for complicated disease.

• Traditional cutoff for positive test is >100,000 colony-forming units/mL. However, many women with cystitis have lower counts so this is an insensitive measure.

• Escherichia coli is the most common organism; others include Klebsiella pneumoniae, Proteus mirabilis, and gram-positives such as Staphylococcus saprophyticus, Enterococcus faecalis, and Streptococcus agalactiae.

Asymptomatic bacteriuria: Be aware of the possibility of asymptomatic bacteriuria, defined by the Infectious Diseases Society of America (IDSA) as “isolation of a specified quantitative count of bacteria in an appropriately collected urine specimen obtained from a person without symptoms or signs referable to urinary infection.” Patients with chronic disabilities causing impaired voiding or with chronic indwelling catheters have a high prevalence of asymptomatic bacteriuria.

• Treatment does not improve outcomes and is not indicated except in pregnant women or patients undergoing urologic procedures with mucosal bleeding.

• Treatment may be considered (although evidence is poor) in catheter-associated asymptomatic bacteriuria that persists 48 hours after short-term (<3 days) indwelling-catheter removal in women to reduce the risk of subsequent infection.

Sterile pyuria is the persistent finding of WBCs in the urine in the absence of a positive culture. The differential diagnosis is broad and requires various diagnostic methods and treatment, depending on the cause. One algorithm for the assessment of a patient with sterile pyuria can be found here.

Treatment

Given the accuracy of symptoms for diagnosis, antibiotics can be given to some patients without in-person assessment. Empiric treatment should be based on local resistance patterns. General IDSA guidelines emphasize minimizing ecologic damage and avoiding selection for drug-resistant organisms.

Empiric Treatment of Acute Uncomplicated Cystitis

Antibiotic	Regimen	Notes
First-line therapy
Nitrofurantoin
Fosfomycin	100 mg BID x5 days
3 g in a single dose

• Concentrate adequately only in urine

• Avoid if suspecting pyelonephritis

| | Trimethoprim–sulfamethoxazole
(TMP-SMX) | 160 mg + 800 mg (double
strength) BID x3 days |

• More ecologic adverse effects than
  other first-line agents

• Avoid if local resistance >20%

• More common side effects

| | Second-line therapy | | Fluoroquinolones
Ciprofloxacin
Levofloxacin | 250 mg BID daily x3 days
250 or 500 mg daily x3 days |

• Reserve for use other than cystitis

• Resistance in U.S. rising and high
  in some regions of the world

| | Beta-lactams (e.g., amoxicillin–
clavulanate, cefdinir, cefaclor,
cefpodoxime) | 3–7 days |

• Generally inferior efficacy and
  more adverse effects

• Alternative when other agents
  cannot be used

|

Abbreviation: BID, twice a day

(Adapted from Uncomplicated Urinary Tract Infection. N Engl J Med 2012.)

Complicated****cystitis may be associated with more drug–resistant organisms and may require broader-spectrum antibiotics for longer durations. Consider a patient’s prior microbiological data and local resistance patterns when selecting an agent (see pyelonephritis treatment below).

Recurrent episodes: Change to another first-line antibiotic if recurrence is within 6 months and review potential nonantimicrobial and antimicrobial strategies for prevention. For example, increasing water intake may help reduce the likelihood of recurrent UTI. 

Pyelonephritis

Acute pyelonephritis is inflammation of the renal pelvis and kidney. It is a severe UTI syndrome that can lead to sepsis, septic shock, and death.

Diagnosis

Symptoms

• fever (not always present)

• chills

• flank pain

• costovertebral-angle tenderness

• nausea or vomiting, with or without symptoms of cystitis (up to 20% of patients do not have bladder symptoms)

Testing

General tests to consider include:

• urine culture: main confirmatory test; pathogens are similar to those causing cystitis

• blood culture: helpful given the high rates of associated bacteremia

• imaging: can identify complications that require further intervention

• • obstruction: ultrasonography for hydronephrosis and CT without contrast for stones

  • abscess and emphysematous infection: CT with contrast

Treatment

The main components of treatment include:

• fluid resuscitation (see Resuscitation Fluids in the Critical Care rotation guide)

• prompt antibiotics

• source control

Select initial antibiotics based on likelihood of a resistant organism (see algorithm below). Hydronephrosis and abscesses may require percutaneous drainage, and emphysematous pyelonephritis typically requires partial or total nephrectomy. 

Proposed Algorithm for the Selection of an Initial Antimicrobial Regimen for Acute Pyelonephritis

(Source: Acute Pyelonephritis in Adults. N Engl J Med 2018.)

Antimicrobial Agents Commonly Used for Treatment of Acute Pyelonephritis in Adults

Antibiotics	Notes
Ciprofloxacin
Levofloxacin
Trimethoprim–
sulfamethoxazole
(TMP-SMX)	Because of possible resistance, initial IV
administration of a supplemental drug is
often warranted

Avoid if local resistance >10% | | Amoxicillin–clavulanate | Active against enterococcus, not for
empiric monotherapy | | Cefixime
Cefpodoxime | Active against many fluoroquinolone- and
TMP-SMX–resistant gram-negative bacilli

Little clinical evidence available | | Piperacillin–tazobactam | Active against some cephalosporin-
resistant gram-negative bacilli | | Ceftriaxone | Active against most fluoroquinolone-
resistant gram-negative bacilli | | Cefepime
Ertapenem
Meropenem
Gentamicin | Active against most fluoroquinolone-
and ceftriaxone-resistant gram-negative bacilli | | Amikacin | Active against many gentamicin-resistant
gram-negative bacilli and New Delhi metallo-
beta-lactamase | | Ceftolozane-
tazobactam
Ceftazidime-avibactam | Active against many resistant gram-
negative bacilli, but not New Delhi metallo-
beta-lactamase |

(Adapted from Acute Pyelonephritis in Adults. N Engl J Med 2018.)

Prostatitis

Prostatitis refers to inflammation of the prostate. Presenting symptoms include pelvic pain, symptoms of cystitis, and obstruction. The National Institute of Health divides prostatitis into four syndromes:

• Acute bacterial prostatitis

• • more common in adults aged 20 to 40 years and older than 70 years

  • presenting symptoms include fever, perineal pain, symptoms of cystitis, obstruction, and occasionally obstructive uropathy

  • the prostate is tender on exam

  • obtain urine cultures to determine the responsible bacteria

  • can be treated with broad-spectrum IV antibiotics (e.g., piperacillin–tazobactam, ceftriaxone with or without an aminoglycoside) or a fluoroquinolone

• Chronic bacterial prostatitis

• • can manifest as recurrent UTIs with the same organism and can be difficult to cure due to poor drug diffusion into the prostate

  • with appropriate suspicion, can be diagnosed with the four-glass Meares–Stamey test

  • usually treated with a fluoroquinolone or TMP-SMX for 30 days

• Chronic nonbacterial prostatitis

• • refers to recurrent symptoms in the presence of inflammation but without bacterial infection of the prostate

• Asymptomatic inflammatory prostatitis

• • refers to incidental evidence of inflammation of the prostate without any urogenital symptoms

Catheter-Associated Urinary Tract Infection

Virtually all health care-associated UTIs are caused by instrumentation of the urinary tract, and catheter-associated urinary tract infections (CAUTIs) increase hospital cost, length of stay, morbidity, and mortality. It’s an important hospital performance measure, and your institution likely has policies to reduce its incidence. The exact case definition has varied over time (see current CDC definition).

Prevention Strategies

• Insert indwelling urinary catheters only when indicated, such as:

• • clinically significant urinary retention or outflow obstruction

  • accurate measurements of urinary output in critically ill patients

  • comfort in terminally ill patients

  • urinary incontinence is not an indication unless to heal open sacral or perineal wounds in incontinent patients

• Assess daily need for ongoing catheter use.

• Consider alternative options such as condom catheter or intermittent catheterization.

• Use aseptic insertion techniques.

• Assure there is no obstruction to flow (e.g., keep collecting bag below level of the bladder at all times).

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