Urinary Tract Infection

Urinary tract infection (UTI) is classified by clinical presentation, not by patient demographics. Uncomplicated UTI is an infection confined to the bladder (cystitis) without systemic features — this now includes men, since sex alone no longer defines complexity. Complicated UTI is defined by systemic signs suggesting infection beyond the bladder: fever, flank pain, bacteremia, sepsis, or association with an indwelling urinary device. Diabetes, older age, or male sex alone do not automatically make a UTI "complicated" under the current classification.^[1] Escherichia coli is the dominant pathogen across all UTI syndromes. Treatment duration for complicated UTI and pyelonephritis is now substantially shorter than older guidance — 5-7 days, not 10-14 — when the patient is responding to effective therapy.^[1]

Infecting organisms by syndrome

Knowing the expected organism by syndrome guides empiric selection before culture results return:

• Sexual intercourse and use of spermicide or a diaphragm.
• Genetic predisposition to recurrent UTI.
• Postmenopausal status with vaginal atrophy.
• Indwelling catheter or recent instrumentation.
• Structural or functional genitourinary abnormality.
• Diabetes and immunosuppression (risk factors for severity, not automatic classifiers of "complicated" disease).
• Pregnancy.

When to culture

Diagnostic thresholds

• Uncomplicated cystitis: any quantitative count of a gram-negative organism or S. saprophyticus in a voided specimen with pyuria supports the diagnosis.
• Pyelonephritis: ≥10⁷ cfu/L (10⁴ cfu/mL) in a voided specimen.
• Complicated UTI: ≥10⁸ cfu/L (10⁵ cfu/mL) voided, or any quantitative count from an in-and-out catheterized specimen.
• Asymptomatic bacteriuria: ≥10⁸ cfu/L in 2 consecutive specimens in women, or 1 specimen in men — and only relevant to test for in pregnancy or before an invasive urologic procedure with expected mucosal bleeding.

Do not over-test

Growing evidence supports relying on clinical judgment rather than reflexive microbial detection — a positive culture in the absence of symptoms is not an indication to treat.^[2]

• Relieve symptoms of acute infection.
• Prevent complications of untreated infection (pyelonephritis, bacteremia).
• Prevent recurrent infection.
• Prevent pyelonephritis and adverse pregnancy outcomes when the patient is pregnant.
• Avoid unnecessary antimicrobial exposure — do not treat asymptomatic bacteriuria outside pregnancy or pre-procedure indications.

• Symptomatic patients should still be offered antimicrobial therapy — NSAID monotherapy instead of antibiotics is associated with a higher rate of complications, including pyelonephritis, and should not be used.^[3]
• Increased water intake is a reasonable, low-risk adjunct for women drinking less than 1.5 L/day, though the effect on recurrence is modest.^[2]
• Avoid spermicide-containing products in patients with recurrent UTI — they are an established risk factor.
• Vaginal estrogen therapy is recommended (not just an option) for peri- and postmenopausal women with recurrent UTI when there is no contraindication.^[2]

Natural health products — what the current evidence actually supports

Pregnancy

Screen for asymptomatic bacteriuria at 12-16 weeks and treat if confirmed on 2 consecutive cultures — untreated bacteriuria in pregnancy can progress to pyelonephritis and cause adverse fetal outcomes.^[6] Follow up with a urine culture 1-2 weeks after completing therapy, then monthly until delivery.

Breastfeeding

Fluoroquinolones, nitrofurantoin, and SMX/TMP are all considered compatible with breastfeeding by the American Academy of Pediatrics. Amoxicillin and cephalosporins are also compatible.

Men

A UTI in a man is uncomplicated only if it is bladder-confined without systemic features; febrile UTI in a man should prompt evaluation for prostatitis or a structural genitourinary cause.^[1]

Uncomplicated cystitis should resolve within a few days of starting therapy; about half of symptomatic patients become symptom-free within 7 days even without antibiotics, but antibiotics reduce symptom burden and duration compared with NSAID monotherapy and should still be offered. Obtain a urine culture if recurrence occurs within 1 month of treatment. For pyelonephritis/complicated UTI, expect clinical improvement (fever resolution, hemodynamic stability) within 48-72 hours — this is the trigger for IV-to-oral switch, not a fixed number of IV days. For pregnancy, follow up with a culture 1-2 weeks after treatment and then monthly until delivery.

1. Confirm the diagnosis — reconsider vaginitis, urethritis, or interstitial cystitis if symptoms don't fit typical cystitis.
2. Obtain a urine culture if not already done, and review susceptibility.
3. Retreat with a different antimicrobial class if the initial agent was anything other than nitrofurantoin (nitrofurantoin may be reused regardless of prior therapy).
4. For recurrence within 1 month, this represents relapse (same organism, incomplete eradication) — investigate for a structural cause or occult renal/prostatic focus rather than simply repeating the same short course.
5. For men or anyone with recurrent same-organism infection, evaluate for chronic prostatitis or a structural abnormality.

• Screening or treating asymptomatic bacteriuria in healthy, nonpregnant patients.
• Classifying every UTI in a man or every UTI in a diabetic patient as "complicated" by default — classification depends on systemic features, not demographics.^[1]
• Using a 10-14 day course for pyelonephritis/complicated UTI when the patient is responding — the current standard is 5-7 days.
• Reaching for a fluoroquinolone as first-line therapy for uncomplicated cystitis.
• Treating chronic pelvic pain in men as prostatitis without microbiologic confirmation.
• Recommending cranberry with the outdated "no evidence" framing — the 2025 AUA guideline now supports offering it (Grade B).
• Relying on D-mannose alone as an effective preventive strategy.
• Performing prostatic massage in suspected acute bacterial prostatitis.

How to use this table: Doses are adult doses and require patient-specific confirmation (renal/hepatic function, weight, allergy history). Pediatric dosing is weight-based per the current product monograph unless stated. Drug pricing is intentionally omitted. Select any drug name to open its complete Pharmasist Drug Database page.

Nitrofuran derivatives (uncomplicated cystitis, 1st line)

Phosphonic acid derivatives (uncomplicated cystitis, 1st line)

Folate antagonists / sulfonamide combinations (uncomplicated cystitis, 1st line)

Cephalosporins (2nd line, or IV empiric for complicated UTI)

Fluoroquinolones (reserve for cases without an alternative in uncomplicated cystitis)

Health Canada has issued a safety warning restricting routine fluoroquinolone use given tendinopathy, neuropathy, and CNS risks.<cite data-reference-id="81b1ad75-4bdb-4b07-a7cc-363efd0b3ec8"></cite>

Penicillins

Aminoglycosides (severe pyelonephritis/prostatitis, initial parenteral therapy)

Switch to oral once signs and symptoms have settled, typically 72-96 hours; short duration keeps oto/nephrotoxicity risk low. Dosing is weight-based and applies across adult and pediatric patients.

Carbapenems (ESBL-producing organisms, severe complicated UTI)