All reproductive age patients when status uncertain
Urine hCG
Serum hCG if ectopic concern
CBC
Systemic features
Leukocytosis
Neutrophilia
Serum creatinine and electrolytes
Concern for obstruction or AKI
Rising creatinine
Hyperkalemia risk with TMP SMX
Blood cultures
Sepsis concern
Two sets prior to antibiotics when feasible
Higher yield in pyelonephritis
STI testing
Dysuria with discharge or cervicitis risk
NAAT for gonorrhea and chlamydia
Trichomonas testing when indicated
Diagnostic Tests
Scoring Systems
Symptom based diagnosis
High pretest probability group
Dysuria and frequency without vaginal discharge
Female nonpregnant
Lower probability group
Prominent vaginal symptoms
Pelvic pain predominant
Complicated infection screen
Fever or flank pain
Immunocompromise
MRI
MRI role
Rare indications
Pregnancy with suspected renal complication and ultrasound nondiagnostic
Suspected spinal source for urinary retention with neurologic signs
Not routine for uncomplicated cystitis
No added value
Resource intensive
CT
CT abdomen pelvis role
Suspected obstruction or stone
CT KUB noncontrast
Hydronephrosis evaluation
Suspected complicated pyelonephritis
Persistent fever beyond 48 to 72 hours on therapy
Severe sepsis or immunocompromised
Suspected renal or perinephric abscess
Persistent flank pain
Bacteremia concern
Not routine in uncomplicated cystitis
No systemic features
No flank pain
Ultrasound
Renal ultrasound role
Hydronephrosis screen
Flank pain with infection
Single kidney
Pregnancy with flank pain
Avoid ionizing radiation
Stone or obstruction assessment
Bladder ultrasound
Post void residual for retention concern
Outlet obstruction concern
Disposition
Site of care decisions
Discharge criteria
Stable vital signs
No hypotension
No persistent tachycardia from sepsis
No systemic toxicity
Well appearing
No altered mental status
Oral intake adequate
Able to take PO antibiotics
No uncontrolled vomiting
Reliable follow up
Return precautions understood
Access to pharmacy
Observation or admission indications
Sepsis concern
Hypotension
Lactate elevated
Suspected pyelonephritis with instability
Persistent vomiting
Intractable pain
Obstruction concern
Hydronephrosis
Anuria
Complicated host
Pregnancy with systemic features
Immunocompromised
Follow up targets
Symptom response window
Improvement within 24 to 48 hours expected
If no improvement by 48 to 72 hours, reassessment and culture review
Treatment
Supportive care
Analgesia strategy
Acetaminophen 1000 mg PO every 6 to 8 hours PRN
Maximum 3000 mg per 24 hours for many adults
Lower maximum with liver disease
Ibuprofen 400 mg PO every 6 to 8 hours PRN
Avoid with AKI risk
Avoid with GI bleed risk
Urinary analgesic option
Phenazopyridine 200 mg PO three times daily
Maximum 2 days with antibiotic initiation
Orange urine discoloration
Hydration
Oral fluids as tolerated
Avoid forced hydration causing discomfort
Reassure urinary frequency may persist early
Antibiotics for uncomplicated cystitis
First line regimens for nonpregnant female
Nitrofurantoin monohydrate macrocrystals 100 mg PO twice daily for 5 days
Avoid if suspected pyelonephritis
Avoid if eGFR very low per local guidance
TMP SMX DS 160 mg 800 mg PO twice daily for 3 days
Use when local E coli resistance under 20 percent
Avoid with sulfa allergy
Fosfomycin trometamol 3 g PO single dose
Lower efficacy than nitrofurantoin in some studies
Useful for adherence barriers
Alternative regimens when first line not suitable
Amoxicillin clavulanate 875 mg 125 mg PO twice daily for 5 to 7 days
Higher recurrence than first line agents
GI adverse effects common
Cephalexin 500 mg PO four times daily for 5 to 7 days
Consider for pregnancy compatible option
Local susceptibility dependent
Cefpodoxime 100 mg PO twice daily for 5 days
Alternative beta lactam
Higher failure than TMP SMX in some settings
Fluoroquinolone stewardship
Ciprofloxacin 250 mg PO twice daily for 3 days
Reserve for intolerance to preferred agents
Avoid when safer options available
Levofloxacin 250 mg PO daily for 3 days
Similar stewardship constraints
Tendinopathy and QT risk
Treatment failure and escalation
Persistent symptoms beyond 48 to 72 hours
Culture review
Switch to susceptible agent
Confirm organism
Reassessment for alternative diagnosis
Vaginitis or STI
Stone or obstruction
Imaging threshold lower with systemic features
Renal ultrasound
CT if high concern
Suspected early pyelonephritis
Oral regimen selection
Fluoroquinolone per local guidance
Beta lactam less preferred without initial IV dose
Initial parenteral option when resistance concerns
Ceftriaxone 1 g IV once
Gentamicin 5 mg/kg IV once
Evidence framing
Short course therapy for uncomplicated cystitis is guideline supported
Class I recommendation based on infectious diseases guideline consensus
Stewardship priority to minimize collateral damage
Special Populations
Pregnancy
Pregnancy considerations
Lower threshold for culture
Culture for symptomatic infection
Test of cure culture often used
Avoided or cautious agents
TMP SMX avoidance in first trimester when alternatives available
TMP SMX avoidance near term with hyperbilirubinemia risk
Nitrofurantoin timing considerations
Avoid near delivery in G6PD deficiency concern
Not for suspected pyelonephritis
Preferred options often used
Cephalexin 500 mg PO four times daily for 5 to 7 days
Amoxicillin clavulanate 875 mg 125 mg PO twice daily for 5 to 7 days
Pyelonephritis in pregnancy
Admission commonly indicated
IV beta lactam therapy common
Geriatric
Older adult considerations
Asymptomatic bacteriuria
Do not treat without urinary symptoms
Common colonization state
Delirium without urinary symptoms
Alternative causes prioritized
UA abnormalities alone insufficient
Medication risks
Nitrofurantoin pulmonary and hepatic rare toxicity risk
TMP SMX hyperkalemia risk
Complicated anatomy more common
Post void residual elevated
BPH related retention
Pediatrics
Pediatric pathway differences
Fever with UTI concern
Upper tract infection more likely
Lower threshold for culture
Weight based antibiotics
Local pediatric guideline dosing
Avoid adult empiric durations without guidance
Anatomic evaluation considerations
Recurrent febrile UTI
Renal ultrasound indications per guideline
Background
Epidemiology
Frequency patterns
Common community bacterial infection in females
Lifetime risk high
Recurrence common
Predominant organism
Escherichia coli majority of cases
Staphylococcus saprophyticus minority
Seasonality and behaviors
Sexual activity associated risk
Spermicide use associated risk
Pathophysiology
Ascending infection model
Periurethral colonization
Enteric flora reservoir
Vaginal microbiome disruption
Bladder mucosal inflammation
Dysuria mechanism
Urgency mechanism
Upper tract progression
Vesicoureteral reflux contribution
Obstruction contribution
Therapeutic Considerations
Antibiotic selection principles
Narrow spectrum preference when feasible
Lower collateral damage
Microbiome preservation
Short course efficacy
Similar cure rates for select agents
Lower adverse event burden
Local antibiogram importance
TMP SMX resistance threshold under 20 percent
ESBL prevalence influences choices
Stewardship constraints
Fluoroquinolone reserve for limited indications
Beta lactam alternatives higher failure risk
Patient Discharge Instructions
copy discharge instructions
Uncomplicated bladder infection diagnosis
Antibiotic course exactly as prescribed
Symptom improvement expected within 24 to 48 hours
Symptom relief
Acetaminophen or ibuprofen as directed
Phenazopyridine use maximum 2 days if prescribed
Hydration and habits
Drink fluids to thirst
Urinate after sex if sexually active
Avoid spermicides if recurrent infections
Return to ED now
Fever 38.0 C or higher
Flank pain
Persistent vomiting
Worsening pain
New confusion
No improvement by 48 to 72 hours
Follow up
Primary care follow up if recurrent symptoms
Culture results review if obtained
References
Guidelines and evidence sources
Evidence sources
IDSA guideline for acute uncomplicated cystitis and pyelonephritis in women
First line agents nitrofurantoin TMP SMX fosfomycin
Short course durations
ACOG guidance for UTI in pregnancy
Culture based management
Pyelonephritis admission considerations
Choosing Wisely recommendations on asymptomatic bacteriuria
Avoid antibiotics without symptoms in most populations
Reduce harm and resistance
CDC STI treatment guidelines
Dysuria with discharge evaluation
NAAT testing recommendations
Instruction source citation
SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.