skip to main content

Post-Operative Oliguria — FRCA Final MCQ

Instant feedback + full explanation. One question, done properly.

EasyPerioperative MedicinePost-Operative OliguriaFRCA Final

A 72-year-old woman weighing 60 kg undergoes an emergency right hemicolectomy under general anaesthesia with a thoracic epidural. During the first 7 postoperative hours, her urine output is 15 mL/hour. Her cumulative fluid balance is −1.5 L after operative blood loss and gastrointestinal losses. Her heart rate is 105 beats/min, blood pressure 95/55 mmHg, capillary refill time 4 seconds and peripheries are cool. Her jugular venous pressure is not visible and her lungs are clear. The urinary catheter is patent and bladder ultrasound shows 20 mL of urine. What is the most likely cause of her oliguria?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: E — Pre-renal acute kidney injury from hypovolaemia

The correct answer is E. Her urine output is 15/60 = 0.25 mL/kg/hour for 7 hours, meeting the urine-output criterion for AKI. The negative fluid balance, blood and gastrointestinal losses, tachycardia, hypotension, prolonged capillary refill, cool peripheries, low JVP and clear lungs indicate hypovolaemia with reduced renal perfusion. A thoracic epidural causes sympathetic blockade and vasodilatation, not direct renal arterial vasoconstriction, although associated hypotension can worsen renal hypoperfusion. Post-renal obstruction is unlikely because the catheter is patent and the bladder is empty. Acute tubular necrosis is less likely without prolonged severe hypoperfusion or a nephrotoxic insult. There are no urinary or systemic features suggesting glomerulonephritis.

Reference: National Institute for Health and Care Excellence. NG148: Acute kidney injury—prevention, detection and management, recommendations 1.1.1, 1.1.13 and 1.3.1. Updated 2024. https://www.nice.org.uk/guidance/ng148/chapter/Recommendations