- Clinical science
Urinary tract infections (UTIs) are classified based on location as upper or lower UTIs, and based on presentation as complicated or uncomplicated. In particular, infection of the bladder is known as cystitis. UTIs are most commonly caused by Enterobacteriaceae, especially Escherichia coli. Women are at high risk of contracting UTIs due to a shorter urethra and the proximity of the anal and genital regions. Other risk factors include sexual intercourse, indwelling urinary catheters, pregnancy, and abnormalities of the urinary tract. Patients present with suprapubic pain, dysuria, urinary urgency and frequency. In typical presentations, clinical diagnosis is often possible and can be supported with findings of pyuria on urinalysis or positive leukocyte esterase and nitrites on a urine dipstick test. Further evaluation with urine culture and/or imaging may be required for patients with complicated cystitis. First-line empiric treatment options for uncomplicated cystitis include trimethoprim-sulfamethoxazole, nitrofurantoin, and fosfomycin. Pregnant women with cystitis should be screened and treated for asymptomatic bacteriuria.
Bacteria: usually caused by an ascending bacterial infection from the urethra
- Enterobacteriaceae (gram-negative rods)
- Viruses: Adenoviruses can cause hemorrhagic cystitis in children and immunocompromised patients.
- Yeast: rare; usually Candida species
- Abacterial, interstitial cystitis (see “Differential diagnosis” below)
Female sex: Women are anatomically predisposed because their urethra is shorter and the anal and genital regions are in close proximity, making it more likely that bacteria might spread from the anal region and colonize the vagina.
- Cystitis in a male patient always merits further urological evaluation.
- Sexual intercourse
- Catheter-associated urinary tract infection (CAUTI): caused by indwelling urinary catheters; most common cause of iatrogenic or
- Host-dependent factors
- Upper UTI : : pyelonephritis
- Lower UTI : : cystitis (most common location of UTIs),
|Uncomplicated UTI|| |
Immunocompetent, premenopausal women that are neither pregnant nor have any condition that predisposes them to an increased risk of infection or failed therapy (see list below)
|Complicated UTI|| |
Any condition or comorbidity that may predispose a patient to an increased risk of infection or failed therapy such as:
|Recurrent UTI|| |
≥ 2 infections/6 months
≥ 3 infections/year
|Nosocomial urinary tract infection|| |
- Clinical diagnosis in healthy women with a typical presentation
- In patients with an atypical presentation, urinalysis is the most important diagnostic test for cystitis.
- Best initial test
- Findings indicative of UTI
Urinalysis with microscopy
- Confirmatory test
- Required in children and adolescents
- Clean-catch midstream specimen is necessary to avoid contamination with vaginal or skin flora. Straight catheterization of the bladder or suprapubic aspiration can also be performed if a clean catch cannot be obtained without contamination (e.g., in children who are not toilet trained.)
Diagnostic criteria for UTI
- Pyuria: ≥5-10 WBC/high power field (hpf)
- Bacteriuria: presence of bacteria on Gram stain (most commonly, gram-negative rods)
- Other possible findings include hematuria and mild proteinuria.
- Leukocyte casts should be absent in lower UTIs.
- Diagnostic criteria for UTI
- Patients with the following characteristics or risk factors:
- Suspected cystitis with the following characteristics:
- Indication: complicated cystitis, suspicion of structural abnormalities
Ultrasound: allows urinary retention to be ruled out; may also show signs of pyelonephritis (see “Diagnostics” of )
- Children <24 months with a urinary tract infection should undergo renal ultrasound in case there is a kidney or urinary tract abnormality
- Cystoscopy: evaluates for unusual findings on urinalysis, stones, reflux, urinary obstruction, polyps or malignancies, and interstitial cystitis
- CT: investigates possible urinary tract pathologies, such as stones, obstruction, tumors, cysts, and trauma
- Intravenous pyelogram (IVP): to look for structural abnormalities, mainly obstructions
- Description: rare, chronic, noninfectious cystitis with an unknown etiology; that causes suprapubic pain and scarring of the bladder wall
- Clinical findings
- Clinical diagnosis after exclusion of other diagnoses
- Urinalysis with microscopy: required to exclude other diagnoses
- Postvoid residual urine volume: may demonstrate urinary retention
- Cystoscopy: performed to rule out other diagnoses, especially bladder cancer. Suspicious lesions should be biopsied.
- Behavior modification (first-line): avoid triggers, fluid management based on symptoms, bladder training
- Oral medications (second-line): Amitriptyline is most commonly used and works as an analgesic and antidepressant.
- Other agents include pentosan polysulfate and antihistamines.
- Invasive procedures in the bladder (third-line)
Other differential diagnoses
- Tuberculous cystitis (see )
- Drug-induced cystitis (e.g., cyclophosphamide, NSAIDs) or radiation-induced cystitis
- Other diseases of the bladder (e.g., urolithiasis, bladder cancer, foreign objects)
- Urethritis with sexually transmitted infections (Neisseria gonorrhoeae, Chlamydia trachomatis, etc.), Candida, or irritants
- Structural abnormalities of the urethra, e.g., diverticula or strictures
The differential diagnoses listed here are not exhaustive.
Principles of therapy
- Supportive treatment (increased fluid intake) may be sufficient, but antibiotic therapy should be recommended.
- Empiric treatment can be given for uncomplicated cystitis; local resistance patterns should guide the choice of empiric therapy.
- Persistent symptoms after 48–72 hours of antibiotic therapy suggest possible complicated cystitis or necessitate that empiric therapy be changed.
- Phenazopyridine, a urinary analgesic, can be used for dysuria for 1–3 days.
- Urine cultures after treatment are not required if the patient's symptoms resolve.
First-line treatment for acute uncomplicated cystitis in nonpregnant women
Trimethoprim-sulfamethoxazole (TMP-SMX) (for 3 days): Bactrim© is a well-known name brand.
- Should be avoided in areas with high resistance (> 20%) or in patients who have used it within the last 3 months (unless the pathogen is susceptible to TMP-SMX on culture)
- Nitrofurantoin (for 5 to 7 days): avoid if patient has renal insufficiency or if pyelonephritis is suspected
- Fosfomycin (single dose): avoid in suspected pyelonephritis
- Fluoroquinolones (e.g., ciprofloxacin, levofloxacin)
- Oral cephalosporins (e.g., cefpodoxime, cefdinir)
- Penicillins (e.g., amoxicillin-clavulanate)
- If treatment fails or symptoms worsen, the patient may be treated for complicated cystitis.
- Treatment is extended to 7 days in complicated cystitis.
- Antibiotics of choice
Therapy in pregnant women
- See .
Treatment of recurrent infections
- If the patient becomes symptomatic within 2 weeks after treatment for a prior UTI has ceased, the patient can be restarted on the same treatment for 2 additional weeks and a urine culture should be obtained.
- A single recurrent infection can be treated as an uncomplicated UTI.
- Chemoprophylaxis can be given to patients with > 2 UTIs per year.
We list the most important complications. The selection is not exhaustive.
- Increased fluid intake
- Postcoital voiding
- Removal of urinary catheter if the patient is ambulatory and able to use the toilet independently
- Intermittent straight catheterization is preferred in patients with neurogenic bladder.
- Intermittent catheterization, instead of the placement of an indwelling catheter, also reduces catheter-associated UTIs
- Prophylaxis in recurrent urinary tract infections (see “Treatment of recurrent infections” above)
- Pathogenesis: Pregnancy may increase the risk of recurrent bacteriuria and UTIs due to urinary stasis (caused by increased progesterone), ureteral smooth muscle relaxation and dilation, increased pressure on the bladder from the uterus, and immunosuppression
- Screening for asymptomatic bacteriuria is recommended for all pregnant women in the first trimester.
- Treatment is always required for asymptomatic bacteriuria in pregnancy; because asymptomatic bacteriuria is more likely to lead to pyelonephritis in pregnant women than in nonpregnant women.
- Treatment is tailored to urine culture and susceptibility
- Treatment options include
- Follow-up culture is required.
Treatment of UTIs in pregnant women
- Obtain urinalysis and urine culture
- Empiric treatment options
- Antibiotic therapy is tailored when urine culture and susceptibility results become available.
- Complicated UTI: hospitalization and administration of intravenous antibiotic (also see )
- Follow-up culture is required.
- Uncomplicated UTI
- Complications: preterm labor, low birth weight, ↑ perinatal mortality
Children and adolescents
Urinalysis and urine culture
- Criteria for diagnosis includes both a positive urinalysis; (pyuria; and/or bacteriuria; ) and urine culture (> 50,000 CFU/mL).
- A clean-catch urine sample may be obtained if the child is toilet trained. If not trained, a straight catheterization is necessary.
- Indicated in patients with suspected UTI that fulfill one of the following criteria:
- Females and uncircumcised males of < 24 months of age with one of the following risk factors: either fever of unknown source or of duration > 24 hours, history of UTI, ill appearance, suprapubic tenderness, or nonblack race
- Circumcised boys < 24 months of age with at least two of the above risk factors
- Children older than 24 months with a suspected UTI based on urinary symptoms (see “Clinical features” section)
- Any febrile infant or child with an abnormal urinary tract or family history of urinary tract disease
- Renal and bladder ultrasound
- Voiding cystourethrography (VCUG)
- Urinalysis and urine culture