Urinary Tract Infection (UTI) – 8 Interesting Facts

What is Urinary Tract Infection (UTI)

Urinary tract infection is an infection of any part of the urinary tract. The urinary tract includes the:

  • Kidneys.
  • Ureters.
  • Bladder.
  • Urethra.

These organs make, store, and get rid of pee (urine) in the body.

Interesting Facts

  1. Urinary tract infection in adults is defined as the presence of pathogenic bacteria within the urinary tract in combination with clinical symptoms and/or an inflammatory response to the pathogen
    • Asymptomatic bacteriuria is not considered a urinary tract infection and requires no treatment except in pregnant women
  2. May be defined as lower urinary tract infection (cystitis) or upper urinary tract infection (pyelonephritis), and uncomplicated or complicated (occurring in patients with factors that increase risk of bacterial colonization and decrease the efficacy of therapy)
  3. Escherichia coli is responsible for 85% of community-acquired urinary tract infections and 50% of hospital-acquired urinary tract infections 1
  4. Diagnosis is suspected based on clinical presentation and urinalysis or urinary dipstick results and confirmed with urine culture
  5. Laboratory tests (including CBC with differential, electrolytes, BUN/creatinine, C-reactive protein) and blood cultures are not routinely required, but should be obtained in patients who are hospitalized and/or appear toxic
  6. Imaging studies are not required in most women with urinary tract infections: indicated in men, patients with refractory infection, and other specific subgroups of patients
  7. Given the emergence of resistant bacteria, initial empiric treatment choice may be incorrect, and a switch in therapy may be required depending on susceptibility testing and clinical response 2
  8. Treat with empiric antibiotic therapy selected according to likely pathogen, severity of clinical illness, and presence of predisposing host factors; tailor therapy based on urine culture, susceptibility testing, and clinical response

Follow these instructions at home:

  • Take over-the-counter and prescription medicines only as told by your doctor.
  • If you were prescribed an antibiotic medicine, take it as told by your doctor. Do not stop taking it even if you start to feel better.
  • Drink enough fluid to keep your pee (urine) pale yellow. For most people, this is 6–10 glasses of water each day.
  • Keep all follow-up visits as told by your doctor. This is important.
  • Make sure you:
    • Empty your bladder often and completely. Do not hold pee for long periods of time.
    • Empty your bladder after sex.
    • Wipe from front to back after a bowel movement if you are female. Use each tissue one time when you wipe.

Contact a doctor if:

  • Your symptoms do not get better after 1–2 days.
  • Your symptoms go away and then come back.

Get help right away if:

  • You have very bad pain in your back.
  • You have very bad pain in your lower belly (abdomen).
  • You have a fever.
  • You are sick to your stomach (nauseous).
  • You are throwing up (vomiting).

Summary

  • A urinary tract infection (UTI) is an infection of any part of the urinary tract.
  • If you were prescribed an antibiotic medicine, take it as told by your doctor. Do not stop taking it even if you start to feel better.
  • Drink enough fluid to keep your pee (urine) pale yellow.

What are other possible causes of painful urination?

A painful burning feeling when you urinate is often a sign of a urinary tract infection (sometimes also called a bladder infection). However, painful urination can occur even if you don’t have an infection.

Certain drugs, like some used in cancer chemotherapy, may inflame the bladder. Something pressing against the bladder (like an ovarian cyst) or a kidney stone stuck near the entrance to the bladder can also cause painful urination.

Painful urination can also be caused by vaginal infection or irritation. You might be sensitive to chemicals in products such as douches, vaginal lubricants, soaps, scented toilet paper or contraceptive foams or sponges. If it hurts to urinate after you’ve used these products, you’re probably sensitive to them.

Do I need to see a doctor?

Yes. Painful urination can be a symptom of a more serious problem. You should tell your doctor about your symptoms and how long you’ve had them. Tell your doctor about any medical conditions you have, such as diabetes mellitus or AIDS, because these could affect your body’s response to infection.

Tell your doctor about any known abnormality in your urinary tract, or if you are or might be pregnant. Tell your doctor if you’ve had any procedures or surgeries on your urinary tract or if you were recently hospitalized (less than 1 month ago) or stayed in a nursing home.

If your doctor thinks your pain may be from vaginal inflammation, he or she may wipe the lining of your vagina with a swab to collect mucus. The mucus will be looked at under a microscope to see if it has yeast or other organisms.

If your pain is from an infection in your urethra (the tube that carries urine from the bladder), your doctor may swab it to test for bacteria. If an infection can’t be found, your doctor may suggest other tests.

Detailed Information

Pitfalls

  • Consider the possibility of sexually transmitted disease as a cause of symptoms in patients presenting with apparent urinary tract infection
  • Fever and/or altered mental status may be the only symptoms in cognitively impaired or elderly patients, patients with an indwelling catheter, paraplegia, or quadriplegia
  • Bag urine specimens should not be used for culture owing to unacceptably high false-positive rates

Urgent Action

  • Urgent urologist consultation is required for patients with urinary tract infection in the presence of an obstructing ureteral stone (can cause sepsis) or renal abscess
  • Prompt treatment with an appropriate antimicrobial agent is recommended for all pregnant patients with urinary tract infection or asymptomatic bacteriuria to reduce risk of pyelonephritis

Terminology

Clinical Clarification

  • Urinary tract infection in adults is defined as the presence of pathogenic bacteria within the urinary tract in combination with clinical symptoms and/or an inflammatory response to the pathogen
  • Asymptomatic bacteriuria (bacterial colonization) is not considered a urinary tract infection and does not require treatment

Classification

  • Clinical syndromes
    • Cystitis (lower urinary tract infection)
      • Symptoms reflect bladder involvement
      • No signs or symptoms suggestive of upper urinary tract or systemic infection
    • Pyelonephritis (upper urinary tract infection)
      • Commonly referred to as pyelonephritis
      • Typically begins as a lower urinary tract infection that ascends to the kidneys
      • Symptoms typically include nausea, vomiting, fever, chills, and flank pain, with or without lower urinary tract infection symptoms
  • Risk stratification 4
    • Uncomplicated urinary tract infection
      • Infection in a healthy patient with a structurally and functionally normal urinary tract
      • Includes infections occurring in healthy, nonpregnant, premenopausal women with anatomically normal urinary tract; some classifications include postmenopausal women and men without urinary tract abnormalities in this category
    • Complicated urinary tract infection
      • Infection occurring in patients with factors that increase the risk of bacterial colonization and decrease the efficacy of therapy
      • Consider urinary tract infection in a man to be complicated until underlying abnormalities have been excluded 5
      • Risk factors include: 6
        • Pregnancy
        • Comorbid medical conditions (eg, diabetes, renal failure, neuromuscular disease)
        • Immunocompromise
        • Hospital-acquired infection/multidrug-resistant infection
        • Renal transplant
        • Anatomic or functional urinary tract abnormalities
          • Presence of bladder calculi
          • Urinary retention (anatomic or neurogenic)
          • Benign prostatic hypertrophy
          • Bladder diverticulum
          • Hydronephrosis
          • Renal stones
          • Vesicoureteral reflux
          • Foreign bodies (eg, catheters, drainage tubes, instruments)
          • Genitourinary malignancy
          • Urosepsis
  • Other categories
    • Catheter-associated urinary tract infection
      • Infection occurring in patient with an indwelling urinary catheter or within 2 days of removal of a urinary catheter
    • Recurrent urinary tract infection
      • Repeated infection occurring after documented infection
    • Persistent urinary tract infection
      • Repeated infection with bacteria from original focus of infection

Diagnosis

Clinical Presentation

History

  • Cystitis
    • Symptoms may include:
      • Urinary urgency
      • Frequency
      • Nocturia
      • Dysuria
      • Hematuria
      • Foul-smelling and cloudy urine
      • Incomplete sensation of bladder emptying
      • Pelvic pain
      • Pelvic pressure
      • Urethral pain or burning during/after voiding
      • Nocturnal enuresis
      • Incontinence
    • Nonspecific systemic symptoms may occur
      • Systemic symptoms include:
        • Poor appetite
        • Confusion
        • Irritability
        • Abdominal distention
        • Diarrhea
        • Lethargy
        • Fever (rare)
      • Fever and/or altered mental status may be the only symptoms in cognitively impaired or elderly patients and patients with an indwelling catheter, paraplegia, or quadriplegia
      • Elderly patients often lack cystitis symptoms
  • Pyelonephritis
    • In addition to cystitis symptoms above, pyelonephritis may present with:
      • Fever and chills
      • Abdominal and flank pain
      • Nausea and vomiting

Physical examination

  • Nonspecific findings associated with cystitis include suprapubic fullness or tenderness
  • Findings in patients with pyelonephritis include:
    • General appearance may suggest systemic illness or dehydration
    • Fever (greater than 38°C) and tachycardia may occur
    • Costovertebral angle tenderness
  • Genitalia: atrophy of introital mucosa in women
  • Rectal: prostate tenderness or bogginess in men

Causes and Risk Factors

Causes

  • Majority of urinary tract infections are caused by bacteria ascending from the periurethral region
    • Escherichia coli is responsible for 85% of community-acquired urinary tract infections and 50% of hospital-acquired urinary tract infections 1
    • Gram-negative Enterobacteriaceae, such as Proteus and Klebsiella, and gram-positive Enterococcus faecalis and Staphylococcus saprophyticus are responsible for most other community-acquired infections 1
    • Fungal infections (eg, Candida albicans, Candida glabrata) occur primarily in patients with indwelling catheters 7
  • Rarely, infection occurs by hematogenous spread in immunocompromised patients

Risk factors and/or associations

Age
  • Highest incidence is in young, sexually active women aged 18 to 24 years
Sex
  • Community-acquired urinary tract infections occur most commonly in females 4
Genetics
  • Certain HLA and Lewis blood group factors may increase risk of urinary tract infection by altering host urinary tract defenses 4
Other risk factors/associations
  • Conditions associated with reduced urine flow 4
    • Prostatic hyperplasia, genitourinary malignancy, urethral stricture, outflow obstruction, or bladder calculi
    • Neurogenic bladder
    • Inadequate uptake of fluid
  • Factors that promote bacterial colonization 4
    • Sexual activity
    • Spermicide use
    • Estrogen deficiency
    • Antimicrobial agents that deplete indigenous flora
    • Diaphragm contraception 8
  • Factors that facilitate bacterial ascent 4
    • Urinary catheterization
    • Urinary incontinence
    • Fecal incontinence/perineal soiling
    • Residual urine with bladder wall ischemia
  • Comorbid medical conditions
    • Poorly controlled diabetes
    • HIV
    • Sickle cell disease
    • Gout
    • Analgesic abuse
    • Hypokalemia
    • Hypophosphatemia
    • Pregnancy
    • Spinal cord injury

Diagnostic Procedures

Primary diagnostic tools

  • Suspect urinary tract infection based on clinical presentation 4
    • Suspect catheter-associated urinary tract infection in patients with urinary tract symptoms or signs who are currently catheterized or have been catheterized in the past 48 hours
  • Presumptive diagnosis can be made based on urinalysis or urinary dipstick results and confirmed with urine culture 1
    • 3 methods of urine collection: 4
      • Clean-catch, midstream-void urine
      • Catheterized urine collection 1
        • Catheterization of men not recommended unless they cannot urinate
        • Catheterization of women can be considered if a noncontaminated specimen cannot be collected
      • Suprapubically aspirated urine: used only for patients unable to urinate voluntarily (eg, patients with spinal cord injuries) 1
  • Consider the possibility of sexually transmitted disease as a cause of symptoms in patients presenting with apparent urinary tract infection
  • Exclude pregnancy in women of childbearing age
  • Laboratory tests (including CBC with differential, electrolytes, BUN/creatinine, C-reactive protein) and blood cultures are not routinely required but test results should be obtained in patients who are hospitalized and/or appear toxic
  • Imaging studies are not required in most patients with urinary tract infections 1
    • May be indicated in the following patients:
      • Men
      • Patients who do not respond to therapy
      • Patients with:
        • Signs or symptoms suggesting urinary tract obstruction
        • Febrile infections
        • Recurrent infections (for identification of underlying abnormalities)
        • Poorly controlled diabetes
        • Polycystic kidneys
        • Potential papillary necrosis
        • Neuropathic bladder

Laboratory

  • Urinalysis or urinary dipstick
    • Indicated when symptoms suggest urinary tract infection 1
    • Positive nitrite or moderate pyuria (urine WBCs greater than 50 colony-forming units/mL) and/or bacteruria are accurate predictors of a urinary tract infection 9
    • Positive leukocyte esterase has a sensitivity and specificity that ranges from 64% to 90% for urinary tract infection 4
    • If urinalysis reveals hematuria (greater than 2 RBCs per high-power field) at the time of initial evaluation, repeat urinalysis after the infection has been treated to determine if microhematuria persists
  • Urine culture
    • Typically required for definitive diagnosis and appropriate antibiotic treatment, except for women with clinical presentation consistent with acute uncomplicated cystitis 5
    • Recommended in women with suspected pyelonephritis, refractory or recurrent symptoms, atypical symptoms, pregnancy, and in males 10
    • In general, greater than 100,000 colonies/mL on urine culture is diagnostic 4
    • Bag urine specimens should not be used for culture owing to unacceptably high false-positive rates
    • Lower colony counts may represent infection if specimen obtained by urethral catheterization or suprapubic aspiration
  • Nucleic acid amplification testing for Chlamydia trachomatis and Neisseria gonorrhoeae
    • Recommended in any patient at high risk for sexually transmitted disease
    • Samples from vagina, cervix, or urine can be tested
    • Positive results indicate presence of organism

Imaging

  • Imaging studies are not indicated for routine uncomplicated urinary tract infections
  • Ultrasonography of kidney and bladder
    • Perform to rule out urinary obstruction and/or renal stone disease 11
    • Can detect structural abnormalities and conditions that are risk factors for urinary tract infection, such as nephrolithiasis, urinary retention, hydronephrosis, and perinephric/renal abscess 1
    • Often is initial imaging study used owing to safety and accessibility 12
    • Less sensitive than CT for evaluating potential complications of upper urinary tract infections 12
  • CT
    • Consider if the patient remains febrile after 72 hours of treatment 11
    • Generally preferred imaging study for evaluating complicated urinary tract infections 12
    • More sensitive than ultrasonography and IV pyelography in the diagnosis of acute focal bacterial nephritis, renal and perirenal abscesses, and radiolucent calculi 1
    • Can be used to investigate:
      • Suspected renal abscess
      • Renal or ureteral stones
      • Hematuria
      • Cause of hydronephrosis identified with ultrasonography
  • CT urography
    • Can demonstrate an underlying cause for unresolving infection, such as a renal calculus or papillary necrosis 12
    • Allows assessment of the anatomy and function (ie, perfusion, excretion, and drainage) of the urinary system
    • Can be considered if the patient remains febrile after 72 hours of treatment 11
    • Lower sensitivity than CT in detecting possible complications including perinephric abscess 12
    • Requires the use of IV iodinated contrast material, which can be contraindicated in some patients and exposes patients to ionizing radiation 12

Differential Diagnosis

Most common

  • Vaginitis (eg, atrophic, bacterial, viral, yeast)
    • Inflammation of the vagina, with vaginal discharge and/or vulvovaginal discomfort
    • May be associated with irritative urinary symptoms
    • Differentiated based on history, physical examination, negative urinalysis and culture, and specific testing for sexually transmitted diseases, or Candida
  • Urethritis Chlamydia, Trichomonas
    • Infection-induced inflammation of the urethra; typically caused by a sexually transmitted disease
    • Involves possible urethral discharge, itching, and dysuria; often asymptomatic in women
    • Diagnosis can be assisted by the following:
      • Presence of mucopurulent or purulent urethral discharge
      • In men, urethral smear showing more than 2 leukocytes per oil-immersion field on microscopy
      • In men, first-void urine specimen demonstrating leukocyte esterase on dipstick test or at least 10 WBCs per high-power field on microscopy
    • Differentiated based on history, physical examination, negative urinalysis and culture, and specific testing for sexually transmitted diseases (eg, chlamydia, gonorrhea, trichomoniasis)
  • Prostatitis
    • Inflammation or infection of the prostate gland
    • Forms include acute bacterial prostatitis, chronic bacterial prostatitis, chronic pelvic pain syndrome, and asymptomatic inflammatory prostatitis
    • Digital rectal examination demonstrates tender, boggy prostate
    • Differentiated based on history, physical examination, and results of urinalysis, culture, specific testing for sexually transmitted diseases (eg, chlamydia, gonorrhea, trichomoniasis), and culture of expressed prostatic secretions
  • Interstitial cystitis
    • Characterized by daytime and nighttime urinary frequency, urinary urgency, and pelvic pain and pressure
    • Unknown cause
    • Diagnosis of exclusion
  • Nephrolithiasis
    • Typically presents with renal colic; however, may be similar to pyelonephritis with flank pain, urinary symptoms, nausea, and vomiting
    • Usually accompanied by gross or microscopic hematuria without fever, unless there is coexisting urinary tract infection
    • Concomitant infection with urinary stone is a consideration when patient presents with pain disproportionate to or uncharacteristic of uncomplicated urinary tract infection
    • Noncontrast CT of the pelvis is the preferred imaging study for most patients to identify precise location and size of urinary stones; renal ultrasonography is preferred for children and pregnant patients
    • Differentiated based on suggestive history, presence of hematuria on urinalysis, and demonstration of calculus on an imaging study
  • Overactive bladder
    • Syndrome causing sudden and unstoppable urge to urinate, as well as possible incontinence
    • Differentiated based on history and physical examination coupled with negative results of urinalysis and urine culture
  • Hemorrhagic viral cystitis
    • Presents with typical symptoms of cystitis along with gross hematuria (usually at the beginning of the urine stream and tapering off by the end)
    • Usually associated with an adenoviral or other upper respiratory infection
    • Screening urinalysis will be absent of signs of bacteriuria
    • Differentiated based on suggestive history, presence of hematuria and absence bacteruria on urinalysis, and negative urine culture

Treatment

Goals

  • Alleviate symptoms
  • Eliminate infection with drug therapy

Disposition

Admission criteria

  • Admit patients who are septic or seriously ill
  • Consider admission for patients with persistent high fever, inability to tolerate oral medication or fluids, dehydration, urinary tract obstruction, or intractable pain

Recommendations for specialist referral

  • Consult urologist in cases of:
    • Males with urinary tract infection
    • Abnormality detected on imaging (eg, calculi, hydronephrosis, renal abscess)
    • Microscopic hematuria (3 or more RBCs per high-power field) persisting for more than 4 weeks after completion of urinary tract infection treatment
    • Failed medical therapy
    • Recurrent urinary tract infections when risk factors for complicated urinary tract infections are present, surgically correctable cause suspected, or diagnosis uncertain

Treatment Options

Treat with empiric antibiotic therapy selected according to likely pathogen, severity of clinical illness, and presence of predisposing host factors

  • Tailor therapy based on clinical response and results of urine culture and susceptibility testing 2

Uncomplicated urinary tract infection (eg, acute cystitis in nonpregnant, premenopausal women; acute pyelonephritis in otherwise healthy patients) 13 14 15

  • Nitrofurantoin; give for 7 days or for at least 3 days after urine is sterile; not recommended for men due to inadequate prostate levels 16
  • Trimethoprim-sulfamethoxazole for 3 days, if local resistance for Escherichia coli is less than 20% 11
  • Trimethoprim for 3 to 5 days 10 15
  • Fosfomycin trometanol 3 g (1 dose) 11
  • If above recommended agents cannot be used
    • β-lactam agents, amoxicillin-clavulanate, cephalexin, or cefpodoxime proxetil, for 3 to 7 days
    • Fluoroquinolones, including ofloxacin, ciprofloxacin, and levofloxacin, for 3 days; considered when no other options are available 10
      • Reserve fluoroquinolones for patients who do not have other available treatment options for uncomplicated urinary tract infections; they have been associated with disabling and potentially irreversible serious adverse effects involving the central nervous system, nerves, tendons, muscles, and joints 17

Acute uncomplicated pyelonephritis 15

  • If pyelonephritis is suspected, always perform urine culture and susceptibility testing; tailor therapy based on the infecting uropathogen
  • Recommendations for outpatients
    • Oral fluoroquinolone (eg, ciprofloxacin for 7-10 days or levofloxacin for 5 days) 11 15
      • Give an initial 1-time IV dose of a long-acting parenteral antimicrobial, such as 1 g of ceftriaxone or a consolidated 24-hour dose of an aminoglycoside if the prevalence of fluoroquinolone resistance exceeds 10% 15
    • Oral trimethoprim-sulfamethoxazole for 14 days if the uropathogen is known to be susceptible
      • If trimethoprim-sulfamethoxazole is used when susceptibility is unknown, an initial IV dose of a long-acting parenteral antimicrobial, such as 1 g of ceftriaxone or a consolidated 24-hour dose of an aminoglycoside, is recommended
      • If above agents cannot be used, other alternatives include amoxicillin-clavulanate or cefpodoxime proxetil for 10 to 14 days
  • Recommendations for patients requiring hospitalization 18
    • Initial empiric treatment should include an IV regimen such as: 15
      • A fluoroquinolone (ciprofloxacin or levofloxacin for 7 days)
      • An extended-spectrum cephalosporin or extended-spectrum penicillin (cetriaxone, cefepime, or piperacillin/tazobactam) with or without an aminoglycoside 18
    • Base choice on local resistance data; tailor regimen based on susceptibility results
    • Switch from IV to oral therapy at 48 hours, providing patient is clinically well; complete 7- to 14-day course

Complicated urinary tract infection (including infection in men, catheter-related urinary tract infection) 7 19

  • If feasible, correct any complicating factors (eg, remove a calculus or catheter)
  • Recommended empiric therapy options include: 18
    • Oral fluoroquinolone (ciprofloxacin or levofloxacin) for 5 to 7 days
      • Give an initial 1-time IV dose of a long-acting parenteral antimicrobial, such as 1 g of ceftriaxone or a consolidated 24-hour dose of an aminoglycoside if the prevalence of fluoroquinolone resistance exceeds 10%
    • Oral trimethoprim-sulfamethoxazole or a fluoroquinolone for 7 to 14 days; recommended in men
    • IV ceftriaxone or ampicillin/sulbactam
    • An extended-spectrum cephalosporin or extended-spectrum penicillin (eg, ceftriaxone, cefepime or piperacillin/tazobactam) with or without an aminoglycoside
  • Complicated pyelonephritis or urosepsis (including catheter-related urinary tract infection in severely ill patient)
    • Patient not severely ill (treat as for inpatient treatment of uncomplicated pyelonephritis) 18
      • An IV fluoroquinolone (ciprofloxacin or levofloxacin for 7 days)
      • An extended-spectrum cephalosporin or extended-spectrum penicillin (ceftriaxone, cefepime, or piperacillin/tazobactam) with or without an aminoglycoside
    • Severely ill patients initially add a third-generation cephalosporin, cefepime, or IV piperacillin-tazobactam (with or without an aminoglycoside) or carbapenem 18
      • An IV extended-spectrum cephalosporin or extended-spectrum penicillin (ceftriaxone, ceftazidime, cefepime, or piperacillin/tazobactam)
      • A carbapenem (eg, ertapenem, meropenem)
      • Aztreonam
      • Colistin; if antibiotic resistant
    • Base choice on local resistance data; tailor regimen based on susceptibility results
    • Treat for a total of 14 days

Drug therapy

  • Antimicrobials
    • Penicillins
      • Oral
        • Amoxicillin-clavulanic acid
          • Amoxicillin Trihydrate, Clavulanate Potassium Oral tablet; Adults (every 12 hour regimens): 500 mg amoxicillin with 125 mg clavulanic acid PO every 12 hours for mild/moderate infections and 875 mg amoxicillin with 125 mg clavulanic acid PO every 12 hours for severe infections.
      • IV
        • Ampicillin-sulbactam
          • Ampicillin Sodium, Sulbactam Sodium Solution for injection; Adults: 150 mg/kg/day to 200 mg/kg/day IV divided every 4 to 6 hours is listed as a possible option by the American Family Physicians.
        • Piperacillin-tazobactam
          • Piperacillin Sodium, Tazobactam Sodium Solution for injection; Adults: Usual FDA-approved dose in adults is 3.375 g (3 g piperacillin and 0.375 g tazobactam) IV every 6 hours. In a randomized study, piperacillin-tazobactam 2.5 g (2 g piperacillin and 0.25 g tazobactam) IV every 8 hours was at least as effective as imipenem-cilastatin. Extended-spectrum penicillins recommended for the treatment of women with pyelonephritis.
    • Aminoglycosides
      • Gentamicin
        • 2 possible dosing regimens:
          • Extended-interval dosing
          • Gentamicin Sulfate, Sodium Chloride Solution for injection; Adults: 5 to 7 mg/kg/dose IV/IM. Dosing interval often determined via nomogram and adjusted based on a random level drawn 8 to 12 hours after the first dose; dosing intervals of 24, 36, and, in some cases, 48 to 72 hours, may be necessary. For pyelonephritis, IDSA recommends giving alone or with ampicillin or with extended-spectrum cephalosporin/penicillin.
          • Conventional dosing
          • Gentamicin Sulfate Solution for injection; Adults: 3 mg/kg/day IV/IM divided every 8 hours; doses up to 5 mg/kg/day IV/IM divided every 6 to 8 hours may be required in life-threatening infections. 
    • Nitrofurans 16
      • Nitrofurantoin
        • Nitrofurantoin Oral capsule; Adults: 50 to 100 mg PO every 6 hours. Give for 7 days or for at least 3 days after urine is sterile.
        • Prophylaxis for recurrent urinary tract infections:
          • Nitrofurantoin Oral tablet; Adults: 50 to 100 mg PO as a single dose at bedtime.
    • Monobactam antibiotics
      • Aztreonam
        • Aztreonam Solution for injection; Adults: 500 to 1,000 mg IV/IM every 8 to 12 hours.
    • Cephalosporins
      • Oral
        • Cephalexin
          • Cephalexin Monohydrate Oral capsule; Adults: 1 to 4 g daily, divided in 2 to 4 doses and generally 250 mg PO every 6 hours or 500 mg PO every 12 hours; higher doses for severe infections. Max: 4 g/day. In general, a treatment duration of 7 to 14 days is recommended for most indications.
        • Cefpodoxime-proxetil
          • Cefpodoxime Proxetil Oral tablet; Adults: 100 mg PO every 12 hours for 7 days. Guidelines recommend for 3 to 7 days as alternative therapy for cystitis; use after long-acting IV agent for pyelonephritis for 10 to 14 days.
        • Cefdinir
          • Cefdinir Oral capsule; Adults: 300 mg PO every 12 hours for 10 days; shorter courses (3 to 7 days) may be used for uncomplicated cystitis.
      • IV
        • Cefazolin
          • Cefazolin Sodium Solution for injection; Adults: For mild infection with gram-positive cocci: 250—500 mg IM/IV q8h. For moderate to severe infection: 500—1000 mg IM/IV q 6—8 h. Max: 12 g/day.
        • Ceftriaxone
          • Ceftriaxone Sodium Solution for injection; Adults: 1 to 2 g/day IV/IM given every 24 hours or divided every 12 hours. Treat for 10 to 14 days for pyelonephritis. Single dose before oral therapy may be used in outpatients.
        • Cefepime
          • Severely ill patients:
            • Cefepime Hydrochloride Solution for injection; Adults: 0.5 to 1 g IV/IM every 12 hours for 7 to 10 days for mild-to-moderate infections, and 2 g IV every 12 hours for 10 days for severe infections. IM administration only for mild-to-moderate UTI caused by E. coli.
        • Ceftazidime
          • Ceftazidime Sodium Solution for injection; Adults: 250 mg IV/IM every 12 hours for uncomplicated UTI or 500 mg IV/IM every 8 to 12 hours for complicated UTI.
    • Fluoroquinolones 20
      • Reserve fluoroquinolones for patients who do not have other available treatment options for uncomplicated urinary tract infections; they have been associated with disabling and potentially irreversible serious adverse effects involving the central nervous system, nerves, tendons, muscles, and joints 17
      • Ciprofloxacin
        • Oral
          • Acute, uncomplicated urinary tract infection (acute cystitis)
            • Immediate release
              • Ciprofloxacin Hydrochloride Oral tablet; Adult females: 250 mg PO every 12 hours for 3 days. Due to the risk for serious and potentially permanent side effects, only use in cases where alternative treatment options cannot be used.
            • Once-daily dosing
              • Ciprofloxacin Hydrochloride Oral tablet, extended-release; Adult females: 500 mg PO once daily for 3 days. Due to the risk for serious and potentially permanent side effects, only use in cases where alternative treatment options cannot be used.
          • Mild to moderate urinary tract infection and treatment of severe and/or complicated urinary tract infection, including pyelonephritis
            • Immediate release
              • Ciprofloxacin Hydrochloride Oral tablet; Adults: 250 to 500 mg PO every 12 hours for 7 to 14 days. Clinical guidelines suggest treatment for 7 days for acute outpatient pyelonephritis and for 7 for 14 days for catheter-associated UTI.
            • Once-daily dosing
              • Ciprofloxacin Hydrochloride Oral tablet, extended-release; Adults: 1,000 mg PO once daily for 7 to 14 days.
        • IV
          • Mild to moderate urinary tract infection and treatment of severe and/or complicated tract infection, including pyelonephritis
            • Ciprofloxacin, Dextrose Solution for injection; Adults: 200 to 400 mg IV every 12 hours for 7 to 14 days. Clinical guidelines suggest initial IV dose then 7 days oral therapy for acute outpatient pyelonephritis; treat for 7 to 14 days for catheter-associated UTI.
      • Levofloxacin
        • Oral
          • Uncomplicated urinary tract infection (mild to moderate acute cystitis)
            • Levofloxacin Oral tablet; Adults: 250 mg PO every 24 hours for 3 days. Due to the risk for serious and potentially permanent side effects, only use in cases where alternative treatment options cannot be used.
          • Mild to moderate complicated urinary tract infection or acute pyelonephritis
            • Levofloxacin Oral tablet; Adults: 750 mg PO every 24 hours for 5 days or 250 mg PO every 24 hours for 10 days.
        • IV
          • Mild to moderate complicated UTI or acute pyelonephritis
            • Levofloxacin Solution for injection; Adults: 750 mg IV every 24 hours for 5 days or 250 mg IV every 24 hours for 10 days.
    • Carbapenem
      • Ertapenem
        • Ertapenem Sodium Solution for injection; Adults: 1 g IV or IM daily for 10—14 days; can switch to appropriate PO therapy after at least 3 days, when clinical improvement is evident.
    • Fosfomycin
      • Fosfomycin Tromethamine Oral granules; Adult women: 3 g PO as a single dose.
    • Sulfonamides
      • Sulfamethoxazole-trimethoprim
        • Sulfamethoxazole, Trimethoprim Oral tablet; Adults: 160 mg trimethoprim/800 mg sulfamethoxazole PO every 12 hours. The IDSA recommends treating for 3 days for acute, uncomplicated cystitis and for 14 days for pyelonephritis in females; treat for 7 to 14 days for catheter-associated UTI; FDA-labeled duration is 10 to 14 days.
      • Trimethoprim
        • For the treatment of acute, uncomplicated UTI in regions where the local resistance pattern for E. coli is < 20%
          • Trimethoprim Oral tablet; Adults: 200 mg PO twice daily for 5 days. 11
        • Prophylaxis for recurrent urinary tract infections in women
          • Trimethoprim Oral tablet; Adults, Adolescents, and Children >= 12 years: 100 mg PO qhs, given for 6 weeks to 6 months.

Nondrug and supportive care

  • Encourage adequate oral fluid intake
  • Give IV fluid hydration to patients with clinical dehydration, vomiting, or sepsis
  • Remove any indwelling urinary catheters if possible
  • Relieve urinary tract obstruction if present

Comorbidities

  • Poorly controlled diabetes 7
    • May require longer antibiotic treatment course
    • Double voiding and timed voiding may be necessary to ensure bladder emptying
  • Immunosuppression 7
    • May require longer antibiotic treatment course

Special populations

  • Recurrent urinary tract infections in women 21
    • Recurrent urinary tract infections are defined as 2 or more symptomatic episodes in a 6-month period, or 3 or more symptomatic episodes in 1 year 22
    • May represent relapse or reinfection
    • Management options include:
      • Treat with short courses of antibiotic therapy (3-5 days) at onset of symptoms
      • Prophylactic single dose of trimethoprim-sulfamethoxazole or ciprofloxacin at time of sexual intercourse
      • Long-term prophylactic antibiotic therapy with nitrofurantoin or trimethoprim-sulfamethoxazole 18
  • Pregnant women
    • Treatment with an appropriate antimicrobial agent is recommended for all pregnant patients with urinary tract infection or asymptomatic bacteriuria to reduce risk of pyelonephritis 3
      • Nitrofurantoin for 5 to 7 days (not during first trimester or near term) 7 16 23
      • Amoxicillin or amoxicillin/clavulanate for 3 to 7 days
      • Cephalexin or cefpodoxime for 3 to 7 days
      • Fosfomycin trometanol 3 g (1 dose) 7 23
      • Trimethoprim-sulfamethoxazole for 3 days, if not resistant (not during first trimester or near term) 7
    • Pyelonephritis in pregnant women requires IV antibiotic therapy
    • Obtain urine cultures 1 to 2 weeks after discontinuing therapy and at regular intervals (eg, monthly) throughout gestation; recurrence is common (20%-30%) 7
    • Recurrent urinary tract infections in pregnancy require prophylactic antibiotic treatment 24
    • Patients with a prepregnancy history of urinary tract infection should have repeated screening during pregnancy 7
  • Paraplegic or quadriplegic patients
    • Fever may be the only symptom; therefore, patients often present with pyelonephritis and sepsis
    • Systemic antimicrobial treatment of asymptomatic catheter-associated bacteriuria is not recommended 11
    • Antibiotic treatment is recommended only for symptomatic infection 11
      • Obtain urine culture specimen from freshly placed catheter before starting antibiotics 11
      • After initiation of empiric treatment, typically with broad-spectrum antibiotics based on local susceptibility patterns, the choice of antibiotics might need to be adjusted according to urine culture results 11
    • Long-term antibiotic suppressive therapy is not effective 11

Monitoring

  • Evaluate patients for a clinical response 24 to 48 hours after initiation of therapy
  • Most patients with uncomplicated urinary tract infection and a prompt therapeutic response do not require follow-up culture
  • Obtain follow-up urinalysis and urine culture 2 days after completion of antibiotic therapy or sooner, if infection does not respond to treatment or worsens
  • If urinalysis reveals hematuria (greater than 2 RBCs per high-power field) at the time of initial evaluation, repeat urinalysis after infection has been treated
    • Microscopic hematuria (greater than 2 RBCs per high-power field) that persists more than 4 weeks after urinary tract infection treatment requires further evaluation by a urologist to exclude other causes

Complications and Prognosis

Complications

  • Acute pyelonephritis can result in sepsis, renal abscess, and impaired renal function (including renal failure)
  • In men, urinary tract infection can progress to acute prostatitis and epididymo-orchitis

Prognosis

  • Uncomplicated urinary tract infection treated promptly with appropriate antibiotics has an excellent prognosis
  • Complicated urinary tract infection has a variable prognosis depending on underlying patient comorbidity, development of complications, specific pathogen involved, and pattern of antimicrobial resistance
  • Urinary tract infection with foreign bodies (eg, calculi, stents, catheters) is more challenging to eradicate; recurrence is more likely

Screening and Prevention

Screening

At-risk populations

  • Pregnant women 24
    • Asymptomatic bacteriuria is common and increases risk of symptomatic urinary tract infection, including pyelonephritis
      • Untreated asymptomatic bacteriuria in pregnancy is associated with preterm delivery, intrauterine growth retardation, low birth weight, maternal hypertension, preeclampsia, and anemia
    • Screen all pregnant women for bacteriuria in the first trimester and treat all identified cases of asymptomatic bacteriuria with antimicrobial therapy guided by culture sensitivities for 3 to 7 days

Screening tests

  • Urinalysis (dipstick or microscopic)
  • Urine culture

Prevention

  • Female patients should:
    • Avoid spermicidal agents if possible; use alternative options
    • Void immediately after sexual intercourse
    • Drink at least 6 to 10 glasses of water daily to maintain hydration
    • Avoid vaginal douching
    • Wipe from front to back after bowel movements
    • Keep the perineum dry, using pads for incontinence if necessary, to prevent recurrent urinary tract infection
  • In patients without urinary tract abnormalities who experience recurring urinary tract infections, methenamine is an alternative to antibiotic suppression 25
  • Vaginal estrogens have been shown to decrease urinary tract infection recurrence in postmenopausal women 26
  • There is conflicting information about the role of cranberry supplements in preventing recurrent urinary tract infections, although cranberry supplements are reasonable to try given their tolerability and low adverse effect profile for women with recurring Escherichia coli urinary tract infections 27 28

Sources

Schaeffer AJ et al: Infections of the urinary tract. In: Wein AJ et al, eds: Campbell-Walsh Urology. 11th ed. Philadelphia, PA: Elsevier; 2016:237-303.e12

Cross Reference

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