UTI OSCE — Diagnosis, Antibiotic Prescribing, Complicated vs Uncomplicated, and Catheter-Associated UTI

Why UTI Is Examined

Urinary tract infections are the most common bacterial infections in women and a leading cause of sepsis in elderly patients. They are examined in OSCEs through history-taking stations, urine dipstick interpretation, prescribing stations, and acute management (the elderly patient with confusion — is this a UTI?). Examiners test appropriate diagnosis (not over-diagnosing in asymptomatic patients), correct antibiotic selection, and recognition of complications.

Classification

Symptoms

Lower UTI (cystitis):

• Dysuria (burning on micturition)
• Frequency and urgency
• Suprapubic pain or discomfort
• Haematuria (may be frank)
• Offensive or cloudy urine

Upper UTI (pyelonephritis):

• All lower UTI symptoms PLUS:
• Fever (above 38 degrees C), rigors
• Loin or flank pain and tenderness
• Nausea and vomiting
• Systemically unwell

Urine Dipstick Interpretation

Pitfalls:

• False negative nitrites: organisms that cannot reduce nitrates (Enterococcus, Staphylococcus saprophyticus, Pseudomonas)
• False positive leucocytes: contamination, vaginal discharge
• Always interpret dipstick in clinical context — not in isolation

Antibiotic Treatment (PHE/NICE Guidelines)

Uncomplicated Lower UTI in Women

UTI in Men

• Treat as complicated — 7 days minimum
• Trimethoprim or cefalexin — consider prostate involvement (prostatitis may need 4 weeks)

Pyelonephritis

• Oral: ciprofloxacin 500 mg BD for 7 days OR co-amoxiclav 500/125 mg TDS for 14 days
• IV (if hospitalised): co-amoxiclav 1.2 g TDS or gentamicin (check eGFR)
• Always send urine MC&S and blood cultures before antibiotics

UTI in Pregnancy

• Always treat — even asymptomatic bacteriuria (risk of pyelonephritis and preterm labour)
• Nitrofurantoin 100 mg MR BD for 7 days (avoid in first trimester and at term)
• Cefalexin 500 mg QDS for 7 days if nitrofurantoin unsuitable
• Avoid trimethoprim (folate antagonist — teratogenic in first trimester) and fluoroquinolones (unsafe in pregnancy)

Catheter-Associated UTI (CAUTI)

Principles:

• Treat only if symptoms present (not just positive dipstick or culture alone)
• Symptoms: fever, suprapubic pain, loin pain, haematuria, new delirium (in context of catheter)
• Remove or change catheter before starting antibiotics
• Send catheter sample of urine (CSU) — not a bag specimen (always contaminated)
• Duration: 7-14 days depending on severity; IV if systemically unwell

Prevention of CAUTI:

• Insert catheter only when necessary; remove as soon as possible
• Closed drainage systems; maintain unobstructed flow
• Aseptic technique for insertion; catheter care bundles
• Consider intermittent self-catheterisation rather than indwelling for long-term bladder management

Frequently Asked Questions

"What is the most common causative organism in UTI?"

Escherichia coli (70-90% of uncomplicated UTIs in community women). Other organisms: Klebsiella pneumoniae, Proteus mirabilis (associated with struvite kidney stones — urease-producing), Staphylococcus saprophyticus (second most common in young sexually active women), Enterococcus faecalis. Hospital-acquired and catheter-associated UTIs are more likely to involve resistant organisms (ESBL-producing E. coli, Pseudomonas, Enterococcus).

"What is the difference between contamination and true bacteriuria on MSU?"

True bacteriuria: growth of above 10⁵ colony-forming units (CFU)/mL of a single organism with pyuria (above 10 WBC/mm3 or leucocyte esterase positive). Contamination: mixed growth, below 10⁵ CFU/mL, or growth of multiple organisms — commonly from perineal skin flora (Lactobacillus, coagulase-negative Staphylococcus). Correct MSU collection (midstream, clean catch after genital hygiene, transported to lab within 2 hours or refrigerated) reduces contamination rates.

"How do you manage recurrent UTIs in women?"

Recurrent UTI is defined as 2 or more episodes in 6 months or 3 or more in 12 months. Management: confirm diagnosis with MSU, investigate for structural abnormality (USS), address modifiable risk factors (post-coital voiding, adequate hydration, avoid spermicides, topical oestrogen in post-menopausal women). Options: patient-initiated self-start therapy (prescription given in advance), post-coital antibiotic prophylaxis (single dose of trimethoprim or nitrofurantoin), or continuous low-dose prophylaxis. D-mannose (supplement) has modest evidence for prevention.

"What is sterile pyuria and what causes it?"

Sterile pyuria is the presence of white blood cells in the urine without bacterial growth on standard culture. Causes: genitourinary TB (must exclude in all sterile pyuria — send early morning urine x3 for TB culture and PCR), partially treated UTI, urethritis (Chlamydia, gonorrhoea), interstitial nephritis, polycystic kidney disease, analgesic nephropathy, bladder tumour, urinary calculi, contamination with vaginal leucocytes. Genitourinary TB should always be considered and excluded with appropriate investigations.

"When does a UTI require IV antibiotics and hospital admission?"

Indications for IV antibiotics and admission: pyelonephritis with systemic sepsis features (fever, tachycardia, hypotension), inability to tolerate oral medication (vomiting), failure to respond to oral antibiotics within 48 hours, immunocompromised patients, urinary obstruction (requires urgent urology — relief of obstruction is an emergency), pregnancy with pyelonephritis, and haemodynamic compromise (urosepsis). Elderly patients with delirium attributable to UTI may also warrant admission for monitoring.

Related Posts

• Urine Dipstick Interpretation OSCE — systematic dipstick interpretation including haematuria and proteinuria
• Sepsis and NEWS Score OSCE — recognising urosepsis in the acutely unwell patient
• Haematuria History OSCE — investigating haematuria including UTI and urological malignancy