TAP Block Anatomy — FRCA Primary MCQ

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ModerateAnatomyTAP Block AnatomyFRCA Primary

During an ultrasound-guided lateral transversus abdominis plane (TAP) block, local anaesthetic is deposited in the fascial plane containing nerves supplying the anterolateral abdominal wall. Which two muscle layers bound this plane?

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Reveal the answer and explanation

Correct answer: D — Internal oblique and transversus abdominis

Explanation lettering: B = shown as A · A = shown as B · E = shown as D · D = shown as E

The correct answer is E. In a lateral TAP block, local anaesthetic is deposited in the fascial plane between the internal oblique and transversus abdominis muscles. The thoracoabdominal nerve branches traversing this plane provide somatic innervation to the anterolateral abdominal wall. The plane between external and internal oblique (C) is too superficial and does not contain the principal target neural plexus. Placement deep to transversus abdominis, toward the peritoneum (B), is also incorrect and risks intraperitoneal injection or visceral injury. Rectus abdominis and its sheath are relevant to anterior abdominal wall and rectus sheath blocks, not the conventional lateral TAP target.

Reference: Tsai HC et al. Transversus Abdominis Plane Block: An Updated Review of Anatomy and Techniques. Biomed Research International. 2017. https://pubmed.ncbi.nlm.nih.gov/29226150/