Infectious DiseasesTier 1Disease (DEADMAN)

Urinary tract infections

Description

Infection anywhere along the urinary tract - cystitis (lower tract) vs pyelonephritis (upper tract, renal parenchyma involved)
Uncomplicated (normal anatomy/function, non-pregnant, immunocompetent) vs complicated (structural/functional abnormality, catheter, pregnancy, male, immunosuppressed, obstruction) - drives duration and choice of therapy

Among the commonest bacterial infections; F>>M in younger adults (anatomy), gap narrows in older age (prostatic disease)
~50-60% of women experience at least one UTI in their lifetime
Recurrent UTI - >=2 in 6 months or >=3 in 12 months

E. coli - ~75-85% of uncomplicated UTIs; other Enterobacteriaceae (Klebsiella, Proteus), Staphylococcus saprophyticus (young sexually active women)
Complicated/catheter-associated: broader range - Pseudomonas, Enterococcus, Candida, resistant Gram-negatives
Risk factors: sexual activity, spermicide use, post-menopausal oestrogen deficiency, incomplete bladder emptying, catheterisation, diabetes, obstruction (stones, BPH), pregnancy (physiological ureteric dilatation)

Clinical - symptoms required for diagnosis (see Asymptomatic bacteriuria caveat below)

Cystitis: dysuria, frequency, urgency, suprapubic pain, +/- haematuria
Pyelonephritis: fever, rigors, flank/loin pain, costovertebral angle tenderness, +/- systemic sepsis features, may or may not have preceding lower tract symptoms

Investigations

Uncomplicated cystitis in a young woman with classic symptoms: clinical diagnosis, empirical treatment without culture is acceptable per most guidelines
Midstream urine culture - for pyelonephritis, complicated UTI, recurrent UTI, treatment failure, pregnancy, or male patients
Blood cultures if systemically unwell/pyelonephritis with sepsis features
Imaging (renal tract ultrasound, CT) if obstruction suspected, failure to respond to therapy, recurrent pyelonephritis, or renal/perinephric abscess suspected

Asymptomatic bacteriuria - not UTI, do not treat

Common, especially in older adults, catheterised patients, and pregnancy screening cohorts
Treat only in pregnancy or before an invasive urological procedure - treating it elsewhere causes harm (resistance, C. difficile) without benefit

A. Uncomplicated cystitis

Trimethoprim or nitrofurantoin (avoid nitrofurantoin at eGFR <30-45) first-line per Australian eTG; cefalexin alternative
Duration 3-5 days depending on agent and patient factors
Avoid fluoroquinolones as first-line given resistance and toxicity profile (tendinopathy, QT, CNS effects)

B. Pyelonephritis

Uncomplicated, well enough for oral therapy: trimethoprim/sulfamethoxazole or a fluoroquinolone (if susceptibility known/likely) for 7-10 days; cefalexin where trimethoprim/quinolone unsuitable
Systemically unwell/complicated: IV therapy - typically gentamicin + amoxicillin, or a broad-spectrum cephalosporin, guided by local antibiogram and risk factors for resistant organisms; step down to oral once improving and sensitivities known
Manage as sepsis if shocked (see Septicaemia and septic shock note)

C. Complicated UTI

Broader empirical cover accounting for resistant organism risk (recent antibiotics, hospitalisation, catheter, overseas travel)
Source control - relieve obstruction (stent/nephrostomy), remove/change infected catheter
Longer duration (typically 7-14 days) depending on severity and response

D. Recurrent UTI prevention

Vaginal (topical) oestrogen in post-menopausal women - reduces recurrence
Behavioural measures - hydration, post-coital voiding; cranberry products - weak evidence
Prophylactic low-dose antibiotics (continuous or post-coital) as a later-line option after non-pharmacological measures fail
Investigate for structural/functional abnormality if recurrent pyelonephritis or male patient with recurrent UTI

E. Male UTI

Always regarded as complicated - investigate for prostatic involvement/obstruction; if prostatitis suspected, longer duration (2-4 weeks) with an agent achieving good prostatic penetration (trimethoprim/sulfamethoxazole, fluoroquinolone)

Uncomplicated cystitis - resolves promptly with appropriate short-course therapy
Pyelonephritis - risk of progression to urosepsis, renal/perinephric abscess, and (rarely) emphysematous pyelonephritis in diabetics if inadequately treated
Recurrent pyelonephritis can cause chronic scarring and, rarely, chronic kidney disease
Untreated obstruction with infection (obstructive pyelonephritis) is a urological emergency requiring urgent decompression

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