Renal Physiology
The kidneys maintain homeostasis through filtration, reabsorption, secretion, and excretion, processing 180 L/day of glomerular filtrate to produce 1-2 L urine. Renal blood flow: 20-25% cardiac output (1.0-1.2 L/min),...
What matters first
The kidneys maintain homeostasis through filtration, reabsorption, secretion, and excretion, processing 180 L/day of glomerular filtrate to produce 1-2 L urine. Renal blood flow: 20-25% cardiac output (1.0-1.2 L/min),...
Acute kidney injury (AKI) with rising creatinine and oliguria
2 Feb 2026
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Clinical board
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Urgent signals
Safety-critical features pulled from the topic metadata.
- Acute kidney injury (AKI) with rising creatinine and oliguria
- Hyperkalaemia >6.5 mmol/L with ECG changes
- Severe metabolic acidosis (pH <7.2)
- Urine output <0.5 mL/kg/hour for >6 hours
Exam focus
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- ANZCA Primary Written
- ANZCA Primary Viva
Content status and exam context
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Topic family
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Renal physiology encompasses nephron anatomy and function, glomerular filtration, renal blood flow autoregulation, tubul... CICM Fellowship Written, CICM Fellow
The kidneys maintain homeostasis through filtration, reabsorption, secretion, and excretion, processing 180 L/day of glomerular filtrate to produce 1-2 L urine. Renal blood flow: 20-25% cardiac output (1.0-1.2 L/min),...
Clinical explanation and evidence
Quick Answer
The kidneys maintain homeostasis through filtration, reabsorption, secretion, and excretion, processing 180 L/day of glomerular filtrate to produce 1-2 L urine. Renal blood flow: 20-25% cardiac output (1.0-1.2 L/min), of which 90% cortex, 10% medulla. Glomerular filtration rate (GFR): 125 mL/min (normal, 70 kg male), autoregulated (myogenic response and tubuloglomerular feedback) maintaining constant GFR despite MAP changes (80-180 mmHg). Nephron function: Proximal tubule (reabsorbs 65% Na⁺, Cl⁻, HCO₃⁻, 100% glucose/amino acids), Loop of Henle (countercurrent multiplication creating medullary osmotic gradient), Distal tubule and collecting duct (aldosterone-sensitive Na⁺ reabsorption and K⁺ secretion, ADH-sensitive water reabsorption). Acid-base: Renal compensation for respiratory disorders (3-5 days full effect), HCO₃⁻ reabsorption (90% proximal tubule, 10% distal), H⁺ secretion (intercalated cells type A), NH₄⁺ excretion (major H⁺ buffer). Anaesthetic implications: Reduced renal perfusion with hypotension, NSAIDs reduce prostaglandin-mediated afferent arteriole dilation (worsen renal function in hypovolaemia, heart failure), contrast-induced nephropathy, drug clearance altered (morphine-6-glucuronide accumulation in renal failure causing respiratory depression). Indigenous populations have 3-4× higher rates of chronic kidney disease from diabetes and hypertension, requiring careful nephrotoxic drug avoidance and dose adjustments for renally-cleared drugs. [1-10]