Infectious Disease

Urinary Tract Infection (Cystitis)

Bacterial infection of the lower urinary tract causing dysuria, urgency and frequency; most commonly Escherichia coli in women.

Last reviewed 28 Jun 2026 - MedicoMedics editorial team

Pathophysiology

Ascending infection from perineal flora. Uropathogens: E. coli (~80%), Klebsiella, Proteus, Staphylococcus saprophyticus (young women).

Sources: IDSA Uncomplicated Cystitis (Clin Infect Dis 2011;52:e103); Cochrane UTI Rev 2020

Presentation

Dysuria, frequency, urgency, suprapubic pain; absence of fever or flank pain distinguishes from pyelonephritis. Older adults may present with delirium only.

Diagnosis

Urinalysis with nitrites and leukocyte esterase; urine culture >=10^5 CFU/mL (or lower with symptoms). Imaging only for recurrent, complicated or male UTI.

Management

Uncomplicated: nitrofurantoin 100 mg BID x 5 days or fosfomycin single dose or TMP-SMX x 3 days if resistance <20%. Avoid fluoroquinolones. Recurrent: postcoital prophylaxis or self-start therapy.

Sample USMLE-style MCQs

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Question 1

25-year-old woman, dysuria and frequency, no fever. Urinalysis nitrite/LE positive. Best therapy?

Question 2

A 25-year-old with dysuria, no fever. Best empiric therapy?

Question 3

Which pathogen classically causes UTI in sexually active young women?

Question 4

Which new oral first-in-class antibiotic is approved for uncomplicated UTI?

Question 5

Pregnant patient with asymptomatic bacteriuria. Best action?

Question 6

Which is contraindicated in CrCl <30?

Question 7

Pyelonephritis outpatient therapy of choice?

Question 8

Contraindication to nitrofurantoin?

Question 9

Uncomplicated cystitis in area with TMP-SMX resistance >30%. Best empiric?

Question 10

Asymptomatic bacteriuria treated in?

References

Primary guidelines and peer-reviewed sources used for this entry. Reviewed 28 Jun 2026 by MedicoMedics editorial team.

Frequently asked

Why avoid fluoroquinolones first-line?

Tendon rupture, aortic dissection risk and resistance.

Which drug for pregnancy UTI?

Cephalexin, fosfomycin, nitrofurantoin (not near term).

Asymptomatic bacteriuria treatment?

Only pregnancy or before urologic procedures.

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