Sacral Canal Volume 20-30 mL — FRCA Primary MCQ

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ModerateAnatomySacral Canal Volume 20-30 mLFRCA Primary

Regarding the anatomy of the sacral canal caudal epidural block requires identification of the sacral hiatus. The volume of the adult sacral canal is approximately:

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Correct answer: A — 20-30 mL

The adult sacral canal volume is approximately 20-30 mL (though highly variable — range 12-65 mL). For adults caudal epidural block typically uses 20 mL of LA to achieve a block to approximately T10 level. For paediatric caudal (most common regional technique in children) the Armitage regimen uses 0.5 mL/kg (lumbosacral) / 1.0 mL/kg (thoracolumbar) / 1.25 mL/kg (mid-thoracic) of 0.25% bupivacaine.

Reference: RCoA 2021 Primary FRCA Curriculum