Urinary Tract Infections

Exam Cram

• Infections of the urinary system: bladder (cystitis), kidney (pyelonephritis)

• Predominantly gram -ve, Escherichia coli

• Presentations: suprapubic pain, lower urinary tract infection- dysuria, frequency, urgency; o/e suprapubic tenderness

• Investigations: urinalysis- nitrates, leukocytes; urine culture for sensitives

• Management: 

  • • 1. Nitrofurantoin, trimethoprim,  cefalexin PO

      2. Gentamicin, ampicillin IV

Presentation

History

• Lower urinary tract symptoms (LUTS)

  • Dysuria (painful urination)

  • Urinary frequency

  • Incontinence

• Fevers, fatigue, anorexia

• Vomiting (pyeloephritis)

Examination

• Suprapubic tenderness: cystitis

• Renal angle percussive tenderness: pyelonephritis

Definitions

Cystitis: bladder inflammation, usually infective cause

Pyelonephritis: kidney inflammation, usually infective cause

Renal abscess: area of pus not perfused by blood caused by infection

Nephronia: inbetween pyelonephritis and renal abcess on imaging, area of tissue poorly perfused

Management

Oral 

Trimethoprim

• Caution in eGFR < 30

Nitrofurantoin

• Caution in eGFR < 45

Cefalexin

• Safe in pregnancy and reduced eGFR

• Good SE profile

Amoxicillin

• High rates of E.coli amoxicillin resistance

• If cultures shows sensitivities to amoxicillin, its an excellent choice as it:

  • • • Doesn't promote further resistance 

      • Low side effect profile, 

      • Safe in pregnancy

      • CKD

Fosfomycin

3g once off option

Minimal side effect profile, safe in pregnancy & CKD

Last line prior to meropenem, therefore should be used sparingly

Intravenous 

Gentamicin

Nephrotoxic

3-5mg/kg as a standard dose, up to 7mg/ kg if severely unwell

Excellent gram negative cover

First dose most effective, UK often continues for up to 4 days (4 doses)

Other options

• Ampicillin

• Ceftriaxone

• Tazocin

• Meropenem

Deeper Dive

Urinary PCR

Not currently used.

PCR has potential to produce relevant organisms far quicker than culture. Problem is that they may pick up clinically insignificant bacteruria.