Normal urine output: 1.5 to 2L per day (min. output is 500ml/600mOsml)

Oliguria - production of between 100 and 400ml of urine/day

Anuria - production of less than 100 mls of urine/day

Absolute anuria (no urine output) - regarded as due to an obstruction until proven otherwise

Causes

• Pre-renal - check BP/CO (most common cause in hospitalised pts)
  • Hypovolaemia - bleeding, sepsis, dehydration, anaphylaxis
  • ⬇️  SVR - sepsis, drug overdose, anaesthesia
  • Cardiac pump failure - MI, tamponade, arrhythmias
• Renal - Intrinsic kidney disease or iatrogenic
• Post-renal - obstructions to flow (blocked catheter, colic, BPH)

3 main causes of complete anuria

• obstruction
• vascular emergancy e.g. aortic dissection
• severe GN

Management

1. Pre-renal.

AIM - to increase renal perfusion

• Fall in blood pressure or CO: administer IV fluid bolus (500 to 1000mls), then reassess. Can give up to 2000-2500mls
• More careful administration if cardiogenic shock (250 mls crystalloid)
• Patients may require an ionotrope (dobutamine) or vasopressor (noradrenaline)