Urinary Tract Infections

Exam Cram

• UTI refers to infections of the urinary system: bladder (cystitis) and kidney (pyelonephritis), predominantly caused by gram -ve bacterial from the bowel, typically Escherichia coli

• Presentations: suprapubic pain, lower urinary tract infection- dysuria, frequency, urgency; o/e suprapubic tenderness; investigations: urinalysis- nitrates, leukocytes; urine microscopy: raised WCC, urine culture gram -ve growth

• Diagnosis: clinical

• Management: 

  • • 1. PO Nitrofurantoin, trimethoprim, cefalexin 

      2.  IV Gentamicin

Outline

Background

• Urine infections can cause inflammation in lower urinary tract (bladder & urethra) causing lower urinary tract symptoms (dysuria, incontinence, urinary frequency) or inflammation in upper urinary tract (kidney & ureter) causing flank pain

• Kidney infections (pyelonephritis) is a more severe infection, associated with urinary sepsis- presenting with fevers, vomiting, drowsiness

• UTIs are more common in females due their shorted urethra and the majority of infections come from the bowel

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: in-between pyelonephritis and renal abcess on imaging, area of tissue poorly perfused

Presentation

History

• Lower urinary tract symptoms (LUTS): dysuria (painful urination), urinary frequency, incontinence

• Upper urinary tract symptoms: flank pain

• Systemic upset (sepsis): fevers, fatigue, anorexia, vomiting

• Background: previous UTIs, abnormal urinary or nervous system anatomy

Examination

• Suprapubic tenderness: cystitis

• Renal angle percussive tenderness: pyelonephritis

• Septic: tachycardia, hypotensive, tachypnoea, febrile

• Catheter in situ: urethral, suprapubic; normal neurology

Investigations

• Urine dip: +ve leukocytes & nitrates

• Urine microscopy: raised WCC (normal SCC)

• Urine culture: +ve growth (gram -ve)

• Bladder scan ?retention

• Inflammatory response: raised WCC & CRP

Diagnosis

• Diagnostic criteria: clinical- based of history, examination, obs & investigations

• Differentials

  • Sepsis unknown source, intrabdominal sepsis- perforation, diverticulitis; chest sepsis

  • Bladder retention from cauda equina

• Classification

  • Severity & location: 

    • Upper urinary tract & septic features = IV antibiotics

    • Lower urinary tract & no septic features = PO antibiotics

    • Septic features (qSOFA): confusion, tachypnoea, hypotension

    • Catheter or non catheter related

Management

Acute

If Cystitis & nil septic features: 

• Antibiotics PO (as per previous urine sensitivities)

  • Nitrofurantoin, trimethoprim, cefalexin, amoxicillin

• Lifestyle: encourage PO fluids

• Discharge/ manage in community

If pyelonephritis & septic features: 

• Antibiotics IV (as per previous urine sensitivities)

  • IV gentamicin +- ampicillin

• Fluid assessment: usually require IVF, c.2L till passing clear urine

• Investigations

  • Lactate, input/output, blood & urine cultures, consider septic screen (CXR, viral PCR,  urine culture)

  • Bladder scan +- IDC/ neuro exam +- change IDC/ SBP catheter

  • Imaging: CTKUB ?stone

• Hospital admission 2-7d

Secondary Prevention

• Long term antibiotic prophylaxis usually not required

• Consider Hipprex (Methenamine) or vaginal oestrogen

• Encourage PO fluids, wipe from to back, safety netting to seek early medical advice

Admission CYcle

Admission

Indications

• Requires IV antibiotics: 

  • Septic features (qSOFA): confusion, tachypnoea, hypotension

  • Vomiting (or diarrhoea): not absorbing PO

• Not coping at home (with symptom burden)- lethargy, confusion, abdo pain

• Requires IV fluids: vomiting, hypovolaemia, AKI

Optimising ward medical management

1. Antibiotics

   • As per previous urine sensitives 

   • As per local trust policies

   • IV Gentamicin: 3mg/kg once off

2. Fluid review

   • Likely dehydrated, reasonable to aim 2L fluid boluses & escalate to HDU & review duiretics

   • Aim MAP > 65, monitor urine output aim 0.5ml/kg/hr (e.g. 40mls/hr)

   • Medication review: stop ACE inhibitors, 

3. Investigations

   • Baseline bloods: FBC, urea & electrolytes, LFTs, CRP

   • Septic screen: urine & blood culture, lactate; consider chest XR, respiratory viral PCR

   • B-HCG if female 15-55 years

   • Imaging: CTAP vs CTKUB vs AUSS- ?urinary stone ?hydronephrosis

4. Consults: 

   • Urology if abnormal anatomy

   • Renal if severe AKI

   • Infectious diseases for complex microbiology

5. Housekeeping: vte prophylaxis, escalation status, capacity assessment

Inpatient Reviews

Complications

• Sepsis: septic shock, hypoxia

• Delirium 

• AKI

Escalate location of care

HDU: requiring single organ support

ICU: double organ support or intubation

• Inotropes for BP 

  • End organ hypoperfusion (AKI, reduced GCS) with

  • MAP < 65 or urine output < 0.5ml/kg/hr with 

• Hypoxia

  • NIV- type 2 respiratory failure

  • Intubation

• Agitation from severe delirium

De-escalate to End of Life Care 

• Patient wishes, advanced directive

• Failing management- ward medical or HDU/ ICU

• Frailty & loss of reserve

Deeper Dive

Antibiotics 

Oral 

Trimethoprim

• MoA: anti folate

• Caution in eGFR < 30 or methotrexate use

• Side effects: 

  • Competitive inhibitor of creatinine- cause creatinine rise (not an AKI)

  • Acute interstitial nephritis (true AKI)

Nitrofurantoin

• Caution in eGFR < 45

Cefalexin

• Safe in pregnancy and reduced eGFR

• Good SE profile

• 500mg QID, consider 1g QID if weight > 70kg

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

• Excellent antibiotics particularly in elderly however should be used sparingly as it is the last line prior to meropenem

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

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.