PassFinals
Renal & Urology

Urinary tract infection

Diagnose UTI from the clinical syndrome and appropriate urine testing, distinguish lower infection from pyelonephritis and sepsis, and tailor antibiotics to age, pregnancy, renal function, culture and local resistance.

In a nutshell

Localise UTI as lower tract, pyelonephritis, prostatitis or sepsis; collect urine appropriately, use age- and pregnancy-specific testing, prescribe according to current NICE tables and culture, and reassess promptly if symptoms worsen or fail to improve within 48 hours.

Classic presentation

A patient has dysuria and frequency with or without suprapubic pain, or has fever, flank pain, vomiting or systemic illness suggesting pyelonephritis; infants may present with non-specific fever or poor feeding.

Key points

  • Fever, rigors, flank pain, vomiting or systemic illness should move the case out of a simple cystitis pathway.
  • Send urine culture before antibiotics in men, pregnancy, children, pyelonephritis, recurrent/complicated infection, treatment failure and suspected sepsis.
  • In children, urine testing is age-specific: infants under 3 months need paediatric specialist care; from 3 years, interpret leukocyte esterase and nitrite together.
  • For uncomplicated lower UTI, nitrofurantoin requires suitable renal function and should not be used for pyelonephritis or suspected prostatitis.
  • Pregnancy requires culture and the current pregnancy antibiotic table; pyelonephritis in pregnancy needs specialist or hospital assessment.
  • Review culture and susceptibility results, narrow treatment where possible and do not use empiric amoxicillin unless the organism is susceptible.
  • Symptoms should begin to improve within 48 hours; deterioration or non-response requires reassessment for sepsis, obstruction, resistance, prostatitis or another diagnosis.

First-line investigation

Clinical localisation plus an appropriately collected urine sample; add culture, renal function and sepsis tests according to age, pregnancy, syndrome and severity.

Management

Identify sepsis and upper-tract disease

  • Assess ABCDE and refer or admit for sepsis, obstruction, pregnancy with significant pyelonephritis, inability to take oral treatment, high-risk child or severe systemic illness.2,4,6,7

Collect and interpret urine correctly

  • Culture in men, pregnancy, children, pyelonephritis, recurrent/complicated infection, treatment failure and suspected sepsis; use the age-specific paediatric dipstick strategy.1,2,4

Give syndrome-specific antibiotics

  • Use the current NICE lower-UTI, pregnancy, paediatric and pyelonephritis tables with BNF renal, allergy and interaction checks; nitrofurantoin is for suitable lower UTI, not pyelonephritis or prostatitis.1,2,4,3,8

Treat complications and review cultures

  • Give IV treatment and seek senior or microbiology advice when severely unwell or unable to take oral therapy; review at 48 hours, step down when possible and investigate obstruction or resistant infection.2,6,4

Safety-net every patient

  • Explain fluids, analgesia, antibiotic adverse effects and urgent return criteria; worsening or no improvement within 48 hours needs reassessment.1,2,11

Exam traps

  • Nitrofurantoin is not an appropriate treatment for pyelonephritis because it does not achieve adequate renal-tissue levels.
  • A male patient with fever or pelvic symptoms may have prostatitis and needs a different pathway.
  • Do not apply adult urine-dipstick rules to infants and young children.
  • Do not delay sepsis treatment while waiting for a urine sample or culture.
  • Do not continue a resistant antibiotic just because symptoms have not yet become severe; review microbiology and clinical response.
  • A back-up prescription is an option only for selected non-pregnant women with lower UTI, not for pregnancy, men, children or suspected pyelonephritis.
  • Failure to improve by 48 hours is a prompt to reassess the diagnosis and complications, not an automatic reason to repeat the same drug.

Illustrations

Lower UTI versus pyelonephritisDiagram contrasting bladder symptoms with upper-tract fever, flank pain, vomiting, sepsis risk and antibiotic route.PassFinals · original
Age-specific urine-testing pathwayFlow diagram showing urine collection and dipstick/culture strategies for infants, young children and children aged 3 years or more.PassFinals · original
Culture-led antibiotic reviewFlow diagram linking sample collection, empiric treatment, susceptibility results, narrow-spectrum switch, treatment failure and sepsis escalation.PassFinals · original

Key sources

  1. NICE NG109: Lower UTI antimicrobial prescribing (NG109 current lower-UTI antibiotic recommendations)
  2. NICE NG111: Acute pyelonephritis antimicrobial prescribing (NG111 current pyelonephritis antibiotic, referral and review recommendations)
  3. BNF: Nitrofurantoin (BNF antibiotic monograph for UTI site, renal function and safety)
  4. NICE NG224: Urinary tract infection in under 16s (NG224 recommendations and 2025 sepsis-link update)
  5. BNF: Trimethoprim (BNF antibiotic monograph for UTI prescribing, resistance and interactions)
  6. NICE NG253: Suspected sepsis in adults (NG253 current adult recognition and management of suspected sepsis)
  7. NICE NG143: Fever in under 5s (NG143 paediatric fever risk and referral pathway)
  8. BNF: Cefalexin (BNF antibiotic monograph for adult, paediatric and pregnancy use)
  9. BNF: Co-amoxiclav (BNF antibiotic monograph for susceptibility-led use and renal dosing)
  10. BNF: Amoxicillin (BNF antibiotic monograph for culture-led prescribing)
  11. NHS: Urinary tract infections (Current public information on UTI symptoms and urgent help)
  12. BNF: Paracetamol (BNF monograph for symptom control and safe dosing)
  13. NICE NG224: Update information (NG224 update history including November 2025 cross-reference update)

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.