Medial and lateral needle insertions for subcostal rectus sheath block

For rectus sheath block, the block needle can be inserted from medial to lateral or the reverse. Some clinicians insert the needle from lateral to medial to allow a shallower insertion angle, as shown in this figure. This figure also shows spread of local anesthetic in the targeted space between the RA and the posterior rectus sheath. Note that the TA provides a backstop against inserting the needle too far and potentially through the peritoneum. For further information refer to UpToDate content on rectus sheath block.