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. 2024 Apr 4;18(4):e01761.
doi: 10.1213/XAA.0000000000001761. eCollection 2024 Apr 1.

The Hypoechoic Triangle: A New Sonographic Landmark for Rectus Sheath Block

Balkarn S Thind  1 , Stefan G Simon, Andrew T Gray
Affiliations

The Hypoechoic Triangle: A New Sonographic Landmark for Rectus Sheath Block

Balkarn S Thind et al. A A Pract. .

Abstract

Rectus sheath blocks can provide analgesia for upper abdominal midline incisions. These blocks can be placed on patients who are anticoagulated, supine, and under general anesthesia. However, block success rates remain low, presumably because of the difficulty of placing local anesthetic between the correct fascial layers. Here we characterize a hypoechoic triangle with sonography, an anatomic space between adjacent rectus abdominis segments that can be accessed for easier needle tip and catheter placement. This approach could reduce reliance on hydrodissection to correctly identify the potential space and instead improve block efficacy by offering providers a discrete target for local anesthesia.

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Conflict of interest statement

Conflicts of Interest: See Disclosures at the end of the article.

Figures

Figure 1.
Figure 1.
A, Simulated block showing the transducer placement and needle entry point for transverse (traditional) approach to rectus sheath block from medial-lateral. The right-handed operator usually stands on the left-hand side of the patient with the ultrasound display placed across the table. The umbilicus is shown for reference. B, The corresponding ultrasound image for (A), highlighting the needle approach and the traditional potential space target (arrow). C, Simulated block showing longitudinal approach. D, Corresponding ultrasound image (for C) from the same patient to highlight the large novel target (hypoechoic triangle) for rectus sheath block.
Figure 2.
Figure 2.
A (left), Parasagittal/longitudinal (novel approach) view showing adjacent rectus sheath muscle segments on the same side (RA), the tendinous intersections (TI) between the 2 segments, and underlying hypoechoic triangle (HT). The borders of this real space (as opposed to potential space via the traditional approach) are the thin layer of investing fascia of rectus abdominis muscle (F) and the double layer forming the base (transversalis abdominus [TA] and peritoneum [P]). B (right), In-plane approach of needle tip placement. Bidirectional distribution pattern and crescent spread appearance from injection within the hypoechoic triangle.
Figure 3.
Figure 3.
Transverse view confirming distribution within the rectus sheath segment (lateral distribution of the injection).
See this image and copyright information in PMC

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