UTIs

Classification

• Uncomplicated
• Complicated: episode of infection with increased risk of serious complications or treatment failure
• Upper: loin pain, pyrexia, rigors, malaise
• Lower: frequency, urgency, suprapubic discomfort, dysuria and cloudy offensive urine

Acute pyelonephritis

• Aetiology
  • Haematogenous - often tonsils, carious teeth, cutaneous infections, renal TB
  • Ascending infection - most common - a/w VUR, urinary stasis, calculi
• Microbiology
  • E coli, and other gram negative organisms
  • Urine goes acidic in E coli and streptococcal infections
  • Proteus and staphylococci split urea to form ammonia, which makes the urine alkaline and promotes stone formation
  • Nitrites in urine suggests gram negative organism
• Risk factors
  • Females, especially during childhood, puberty, after intercourse, and during pregnancy
• Presentation
  • Fever
  • Rigors
  • Flank pain
  • N/V
  • Costovertebral angle tenderness
  • Pyuria - almost always
• Workup
  • Urine MCS
  • Renal USS to exclude pyonephrosis, perirenal abscess and obstruction by calculi
  • CT can be done - decreased opacification of affected parenchyma, typically in patchy, wedge-shaped or linear distribution
• Special situations
  • Pregnancy
    • Often presents 20-28 weeks with malaise, fever, loin pain, rigors
    • Not all women will have had LUTS
  • Childhood/VUR
    • Underlying cause - urinary stasis due to VUR, detrusor-sphincter dyssinergia, poor bladder emptying habit or constipation, stones, outlet obstruction, neurological disorders such as spina bifida
    • Should be investigated after first confirmed UTI
    • Can lead to renal scarring in up to 20%, and subsequent HTN
    • VUR diagnosed with micturating cystogram
    • DMSA scan can be used to assess degree of renal scarring
    • Indications for surgery in VUR: recurrent acute pyelonephritis despite Abx or if severe reflux is accompanied by a surgically correctable malformation
  • Renal cortical abscess (carbuncle)
    • Usually caused by Staph aureus, reaching the kidney through haematogenous spread
    • Risk factors: diabetics, IVDU, chronic disease, immunodeficiency
    • May have no urinary symptoms or findings if it does not communicate with collecting system
  • Renal corticomedullary abscess
    • Usually results from ascending UTI in association with an underlying urinary tract abnormality
    • Usually caused by common uropathogens such as GNB/E coli
    • Can extend deep into parenchyma, penetrate capsule and form a perirenal abscess
    • Small abscesses can be treated with antibiotics, but perc drainage is often needed to stabilise the patient, and may need a nephrostomy too
  • Emphysematous pyelonephritis
    • Fulminant, necrotising, life-threatening variant of acute pyelonephritis caused by gas-forming organisms
    • 90% occurs in diabetic patients
    • Gas will be seen on plain film, USS or CT
    • Broad spectrum Abx and percutaneous drainage for mildly unwell patients
    • Severely unwell patients may need nephrectomy
  • Xanthogranulomatous pyelonephritis
    • Uncommon but severe chronic destructive granulomatous inflammation of renal parenchyma, associated with obstruction and infection of the urinary tract
    • Typically middle-aged women with chronic symptoms - flank pain, pyrexia, malaise
    • MCS usually positive for E coli/GNB or S aureus
    • CT - enlarged, non-functioning kidney, often with calculi and low-density masses (xanthomatous tissue) and in some cases involvement of adjacent structures - sometimes difficult to distinguish from neoplastic disease
    • Nephrectomy is usually needed
  • TB of urinary tract
    • Always haematogenous - secondary TB
    • Formation of granulomas
    • Involvement of bladder secondary to renal disease
    • Generally have TB in urine

Cystitis/lower urinary tract infection

• Presentation
  • Frequency
  • Urgency
  • Suprapubic discomfort
  • Dysuria
  • Cloudy offensive urine
• Pathophysiology
  • Often a/w upper tract colonisation
  • Recurrent infection:
    • ?underlying predisposing cause
      • Incomplete emptying of the bladder - BOO, bladder diverticulum, neurogenic bladder dysfunction, decompensation of detrusor muscle
      • Calculus, foreign body or neoplasm
      • Incomplete emptying of upper tract, dilation of ureters a/w pregnancy, or VUR
      • Oestrogen deficiency - lowered local resistance
      • Colonisation of perineal skin
      • Diabetes
      • Immunosuppression
    • ?resistant organism
• Investigation
  • Indications:
    • Repeated attacks in women
    • Single episode in a man
    • Single episode in a child of either sex
  • Urinalysis
  • Upper tract imaging
  • Cystoscopy
• Special situations
  • Acute abacterial cystitis - pus in urine but no organism identified.
    • STI
    • TB
    • Carcinoma in situ
    • Mycoplasma
    • HSV
    • Cyclophosphamide
  • Interstitial cystitis