Lower urinary tract infection in non-pregnant, immunocompetent woman with normal anatomy.
Also known as: acute cystitis, uncomplicated UTI, lower UTI, bladder infection
Overview
Inflammation and infection of the bladder mucosa, typically caused by ascending bacterial infection. 'Uncomplicated' refers to cystitis in non-pregnant, premenopausal women with no functional or structural urinary tract abnormality and no relevant comorbidities. Traditionally all other cases (men, pregnancy, catheter, anatomic abnormality, immunocompromise) were labeled 'complicated'; IDSA 2025 instead classifies UTI mainly by clinical extent: infection beyond the bladder (fever, systemic signs, flank pain or CVA tenderness) is complicated, which includes all pyelonephritis.
Epidemiology
Among the most common bacterial infections — ~50% of women experience at least one UTI in their lifetime. Peak incidence in sexually active women aged 18-30 and postmenopausal women. Rare in healthy men under 50.
Try two board-style Acute Cystitis questions
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Question 1RenalMedium
A 35-year-old woman presents with 2 days of dysuria, urinary frequency, urgency, and suprapubic pain. She is afebrile and not pregnant, and has no costovertebral angle tenderness or flank pain. She has no recent antibiotic use, urologic abnormality, or history of multidrug-resistant infection. Urinalysis shows pyuria and positive nitrites. Which of the following is the most appropriate first-line treatment?
AAmoxicillin × 7 days
BNitrofurantoin × 5 days
CCeftriaxone IM × 1 dose
DAmoxicillin-clavulanate × 7 days
ECiprofloxacin × 3 days
Reveal answer & full explanation
Correct answer: B — Nitrofurantoin × 5 days
AAmoxicillin × 7 days
BNitrofurantoin × 5 days✓
CCeftriaxone IM × 1 dose
DAmoxicillin-clavulanate × 7 days
ECiprofloxacin × 3 days
Why Nitrofurantoin × 5 days is correct
The picture is acute uncomplicated cystitis in a healthy, non-pregnant, afebrile woman with no costovertebral angle tenderness, so there are no features of pyelonephritis or a complicated UTI.
Per current IDSA guidance, first-line options are nitrofurantoin monohydrate/macrocrystals for 5 days, trimethoprim-sulfamethoxazole double-strength for 3 days, or fosfomycin as a single 3-g dose.
Nitrofurantoin concentrates in the urine, has low collateral resistance, and is an ideal agent for cystitis.
Why the others are wrong
Amoxicillin-clavulanate × 7 days — Beta-lactams are second-line for cystitis because of lower efficacy and higher relapse rates; selecting it reflects a right-diagnosis-wrong-step trap.
Ciprofloxacin × 3 days — Fluoroquinolones are effective but reserved for more serious infections under antimicrobial stewardship and carry boxed-warning toxicities; buzzword-matching 'UTI equals cipro.'
Amoxicillin × 7 days — IDSA advises against empiric amoxicillin or ampicillin for cystitis because of poor efficacy and widespread E. coli resistance; unlike amoxicillin-clavulanate, it has no beta-lactamase inhibitor to overcome that resistance (confusing it with the acceptable second-line beta-lactam).
Ceftriaxone IM × 1 dose — a single IM ceftriaxone dose is the gonorrhea regimen, and an initial parenteral dose can begin outpatient pyelonephritis treatment, so dysuria with pyuria can trigger it; but she has uncomplicated cystitis without fever or flank pain, which an oral first-line agent such as nitrofurantoin treats without an injection (confusing cystitis with gonococcal infection or pyelonephritis).
Question 2RenalEasy
A 32-year-old woman presents with a 2-day history of dysuria, urinary frequency, and suprapubic discomfort. She is afebrile and has no costovertebral angle tenderness. Urinalysis shows pyuria and bacteriuria. She is not pregnant. What is the first-line treatment?
ACeftriaxone 1 g IM for 1 dose
BNitrofurantoin 100 mg BID for 5 days
CCephalexin 500 mg BID for 7 days
DCiprofloxacin 500 mg BID for 7 days
EAmoxicillin 500 mg TID for 7 days
Reveal answer & full explanation
Correct answer: B — Nitrofurantoin 100 mg BID for 5 days
ACeftriaxone 1 g IM for 1 dose
BNitrofurantoin 100 mg BID for 5 days✓
CCephalexin 500 mg BID for 7 days
DCiprofloxacin 500 mg BID for 7 days
EAmoxicillin 500 mg TID for 7 days
Why Nitrofurantoin 100 mg BID for 5 days is correct
This is uncomplicated lower urinary tract infection (UTI) (cystitis) in a non-pregnant woman.
First-line options per Infectious Diseases Society of America (IDSA) guidelines: nitrofurantoin (5 days), trimethoprim-sulfamethoxazole (TMP-SMX) (3 days if local resistance is below 20%), or fosfomycin (1 dose).
Nitrofurantoin is preferred due to low resistance and minimal collateral damage to gut flora.
Why the others are wrong
Ciprofloxacin 500 mg BID for 7 days — fluoroquinolones are reserved for complicated UTI or pyelonephritis, not uncomplicated cystitis.
Amoxicillin 500 mg TID for 7 days — amoxicillin has high E. coli resistance and is not recommended.
Ceftriaxone 1 g IM for 1 dose — ceftriaxone is for pyelonephritis or complicated cases, not uncomplicated cystitis.
Cephalexin 500 mg BID for 7 days — cephalexin is a common choice for cystitis in pregnancy, but in a nonpregnant woman oral cephalosporins are second-line alternatives that are generally less effective than first-line agents and are reserved for when a first-line agent such as nitrofurantoin, TMP-SMX, or fosfomycin cannot be used.
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Uropathogens (most commonly uropathogenic E. coli, ~80%) ascend from the urethra into the bladder. Bacterial adhesins (fimbriae) attach to uroepithelial cells; invasion triggers inflammatory response with neutrophil infiltration. Symptoms reflect bladder mucosal irritation rather than systemic illness.
Clinical presentation
Symptoms
Dysuria (burning with urination)
Urinary frequency, urgency
Suprapubic pain or discomfort
Cloudy or malodorous urine; sometimes gross hematuria
Absence of fever, flank pain, or systemic symptoms (presence suggests pyelonephritis)
Signs / physical exam
Often unremarkable exam
Mild suprapubic tenderness on palpation
Absence of CVA tenderness, fever, or hemodynamic compromise
Pelvic exam if vaginitis or STI suspected
Classic findings
Sexually active young woman with sudden dysuria, frequency, and urgency without vaginal discharge or fever — empiric treatment without urine culture is reasonable.
Urethritis (STI) — Gonorrhea, chlamydia, trichomonas; sexually active patient, partner symptoms, sterile pyuria with negative routine culture
Vaginitis — Vaginal discharge, pruritus, dyspareunia; positive wet prep, KOH, or whiff test
Interstitial cystitis — Chronic pelvic pain, urinary frequency without infection, negative cultures
Overactive bladder — Frequency, urgency without infection; positive bladder diary
Bladder cancer — Older patients (smokers), painless gross hematuria, recurrent 'UTI' with negative culture
Diagnostic workup
Diagnostic criteria
Clinical diagnosis based on symptoms (dysuria, frequency, urgency, suprapubic pain) supported by pyuria. Urine culture with ≥10^5 CFU/mL (or ≥10^3 CFU/mL with symptoms) confirms but is often not necessary for treatment initiation in classic cases.
Labs
Urinalysis (dipstick or microscopy) — pyuria (>10 WBCs/HPF or positive leukocyte esterase), bacteriuria, nitrites (gram-negative bacteria reduce nitrate to nitrite)
Urine culture — not required in uncomplicated cystitis with classic symptoms but recommended in: recurrent UTI, treatment failure, complicated UTI, pregnancy, men, suspected pyelonephritis
Beta-hCG in women of reproductive age if treatment selection or pyelonephritis concern
STI testing (NAAT for GC/CT) if sexually active and risk factors
Imaging
Not required for uncomplicated cystitis
Imaging (US or CT) considered for recurrent, complicated, or treatment-resistant UTI to evaluate for stones, abscess, anatomic abnormality
Diagnostic algorithm
Antibiotic
Dose / Duration
Notes / Cautions
Nitrofurantoin
100 mg PO BID × 5 days
Avoid if eGFR <30, pyelonephritis suspected, near term pregnancy
TMP-SMX
1 DS tab PO BID × 3 days
Avoid if local resistance >20% or prior 3-month use; avoid in 1st trimester and near term
Fosfomycin
3 g PO × 1 dose
Single dose; less effective than 5-day regimens
Cephalexin
500 mg PO BID × 5-7 days
Second-line; safe in pregnancy
Amoxicillin-clavulanate
500 mg PO BID × 5-7 days
Second-line; safe in pregnancy
Fluoroquinolones
Reserve for pyelonephritis or complicated UTI
FDA black box for uncomplicated cystitis
IDSA-recommended antimicrobial regimens for acute uncomplicated cystitis in adult women.
Treatment
First-line
Nitrofurantoin monohydrate/macrocrystals 100 mg PO BID × 5 days (avoid if eGFR <30 or pyelonephritis suspected)
Trimethoprim-sulfamethoxazole (TMP-SMX) DS PO BID × 3 days — use only if local resistance <20% and patient not exposed in prior 3 months
Fosfomycin 3 g PO × 1 dose — convenient single dose; less effective than 5-day regimens
Avoid fluoroquinolones for uncomplicated cystitis (FDA black box; reserve for complicated UTI/pyelo)
Symptomatic relief: phenazopyridine (Pyridium) for dysuria — ≤2 days, warn about orange urine; avoid in G6PD deficiency
Second-line / adjunct
Beta-lactams (amoxicillin-clavulanate, cefpodoxime, cefdinir) — second-line; less effective than first-line agents
For recurrent UTI (≥2 culture-proven episodes in 6 months or ≥3 in 12 months): single-dose postcoital prophylaxis when episodes follow intercourse, otherwise continuous low-dose prophylaxis (nitrofurantoin, TMP-SMX, cephalexin) for 6-12 months, or self-start therapy; methenamine hippurate is a non-antibiotic option
Postmenopausal women: vaginal estrogen for recurrent UTI (reduces frequency)
Cranberry products — modest evidence; not a replacement for antibiotics in acute UTI
Pregnancy: cephalexin, amoxicillin-clavulanate, nitrofurantoin (NOT in 1st trimester or near term), or fosfomycin; AVOID TMP-SMX in 1st trimester and near term; AVOID fluoroquinolones
Complications
Progression to pyelonephritis if untreated or treatment failure
Recurrent UTI (re-infection or relapse)
Pregnancy: untreated UTI increases risk of pyelonephritis (up to 30%), preterm labor, low birth weight
Antibiotic-associated complications: C. difficile colitis, allergic reactions, antimicrobial resistance
Rare: bacteremia/urosepsis in compromised hosts
PANCE pearls
Classic dysuria + frequency in a young healthy woman without vaginal symptoms can be treated empirically without urinalysis or culture (per IDSA).
Nitrites positive = gram-negative organism reducing nitrate; absence does NOT exclude UTI (gram-positives like Staph saprophyticus and Enterococcus don't produce nitrites).
Asymptomatic bacteriuria should be treated ONLY in: pregnancy and before urologic procedures with mucosal trauma. Do NOT treat asymptomatic bacteriuria in elderly, diabetics, catheter, or general population.
Pyuria without bacteriuria (sterile pyuria) = consider urethritis (STI), TB, interstitial cystitis, or partially treated UTI.
In men, cystitis is uncommon: obtain a urine culture, treat about 7 days (7 days is as effective as 14 in afebrile men), treat longer if acute bacterial prostatitis is suspected (fever, perineal or pelvic pain, tender prostate), and evaluate for an underlying cause (BPH, prostatitis, stones). Under IDSA 2025, male sex alone no longer makes a UTI 'complicated'; extension beyond the bladder does.
References
IDSA 2011 — International Clinical Practice Guidelines for the Treatment of Acute Uncomplicated Cystitis and Pyelonephritis (Gupta et al., CID 2011)
AUA/CUA/SUFU 2025 — Updates to Recurrent Uncomplicated Urinary Tract Infections in Women: AUA/CUA/SUFU Guideline (2025) (Ackerman et al., J Urol 2026)
USPSTF 2019 — Screening for Asymptomatic Bacteriuria in Adults: USPSTF Recommendation Statement (Owens et al., JAMA 2019)
IDSA 2025 — Clinical Practice Guidelines by IDSA: 2025 Guidelines on Management and Treatment of Complicated Urinary Tract Infections (Trautner et al., Clin Infect Dis 2026;82 Suppl 3)
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