Revisiting the deep rectus sheath block: An anatomical mismatch for optimal analgesia

Dear Editor,

We read with great interest the article by Marrone et al.[1] on the application of the deep rectus sheath (DRS) block for postoperative analgesia following laparoscopic cholecystectomy. While the reported clinical outcome of the presented case is noteworthy, we would like to raise certain anatomical and conceptual concerns regarding the mechanism proposed for visceral pain relief through this technique.

In 2024, Fusco et al.[2] described an ultrasound-guided DRS block designed to provide visceral analgesia by depositing local anaesthetic (LA) in the preperitoneal space. Marrone et al.[1] also mentioned LA injection into ‘the preperitoneal space under DRS, just above the umbilicus’. Thus, the DRS block is fundamentally an ultrasound-guided adaptation of anterior abdominal preperitoneal LA deposition first described by Deans et al. in 1998.[3] From an anatomical perspective, proximal to the arcuate line and beyond the costal cartilages, the structures lying deep to the posterior rectus sheath (PRS) include the transversalis fascia (TF), extraperitoneal fat, connective tissue, and the parietal peritoneum (PP).[4] Distal to the arcuate line, the PRS is absent, and the rectus abdominis muscle (RAM) lies directly over the TF [Figure 1a]. Two distinct compartments are present: one between the PRS and the TF, and another between the TF and the PP. However, the PRS and TF are closely adherent and may not always be separately identifiable by ultrasound. In contrast, the preperitoneal space between the PRS–TF complex and PP is clearly visualised [Figure 1b–d]. In the ultrasound image provided in the article[1], the TF is not depicted, and the LA appears between the PRS and the PP, described as the preperitoneal compartment, representing an anatomically incomplete depiction.

Figure 1.

Anatomy and corresponding sonoanatomy of the anterior abdominal wall. a: Paramedian sagittal section of the left anterior abdominal wall. 1, 2, 3 = positions of ultrasound transducer in transverse plane. b: Sonoanatomy above the costal margin. c: Sonoanatomy between the costal margin and arcuate line (AL). d: Below the AL. CC = costal cartilage (5, 6, 7, 8, 9, 10); D = diaphragm; DF = diaphragmatic fascia; ARS = anterior rectus sheath; PRS = posterior rectus sheath; SEV = superior epigastric vessels; IEV = inferior epigastric vessels; SuEV = superficial epigastric vessels; RAM = rectus abdominis muscle; TAM = transversus abdominis muscle; EOM = external oblique muscle; AC = abdominal cavity; PP = parietal peritoneum; TF = transversalis fascia; U = umbilicus; PPS = preperitoneal space; LCT = loose connective tissue; SF = subcutaneous fat/superficial fascia; LA = linea alba; EIM = external intercostal membrane; IIM = internal intercostal muscle

The port sites in laparoscopic cholecystectomy typically correspond to T6–T10 dermatomal distribution. The thoracolumbar nerves enter the transversus abdominis plane (TAP) progressively more laterally [Figure 2a]. Segmental nerves T6–T9 emerge from the costal margin into the TAP between the midline and the anterior axillary line. T9–L1 nerves are extensively branched and communicate within the TAP, forming the TAP plexus [Figure 2b]. Then, they approach the posterior surface of the RAM from its lateral border, creating another plexus before terminating as muscular and cutaneous branches [Figure 2b and c].[5] The PP is innervated by somatic and visceral afferent nerves, the phrenic nerve, and receives sensory branches from the lower intercostal nerves and from the upper lumbar nerves (T6–L1), which also supply the abdominal wall.[6] The PP is highly vascular, making systemic absorption of LA, and consequently, analgesia, a likely contributor following the DRS block. Administration of only the DRS block may offer limited midline PP analgesia. Still, its anatomical limitations fail to address other sources of pain, such as diaphragmatic irritation and inflammation of the gallbladder bed. Hence, the pain is more effectively targeted using thoracic paravertebral, paraspinal, and anterolateral truncal interfascial plane blocks, along with MMA.

Figure 2.

Innervation of the abdominal wall and distribution pattern of thoracoabdominal nerves. a: level of entry of thoracolumbar nerves in the a abdominis plane (TAP). b: Formation of TAP and rectus sheath (RS) plexuses. c: Termination of nerves and innervation of parietal peritoneum (PP) and anterior abdominal wall. ARS = anterior rectus sheath; PRS = posterior rectus sheath; RAM = rectus abdominis muscle; TAM = transversus abdominis muscle; IOM = internal oblique muscle; EOM = external oblique muscle; AC = abdominal cavity; PP = parietal; TF = transversalis fascia; PPS = preperitoneal space; SF = subcutaneous fat/superficial fascia; DCIV = deep circumflex iliac vessels; AAL = anterior axillary line; MAL = mid-axillary line; PAL = posterior axillary line; DIEV = deep inferior epigastric vessels

The proposed involvement of the iliohypogastric and ilioinguinal nerves (IHN-IIN; T12, L1) in the DRS block appears anatomically implausible. Both nerves course obliquely through the posterior abdominal wall, emerging from the lateral border of the psoas major, traversing the anterior surface of the quadratus lumborum, and piercing the transversus abdominis muscle at variable distances to enter the transversus abdominis plane (TAP).[7] Jamieson et al.[8] found both nerves in the TAP, above and posterior to the ASIS, in over 90% of 244 dissections. By the time IHN-IIN reach the midline, they have already traversed superficial layers and are no longer within the preperitoneal plane targeted by the DRS block. Thus, their blockade via midline or anterior injection is unlikely, and attributing analgesia to their involvement lacks both anatomical and physiological basis. This block also resembles the TF plane block described by Ki-Jinn Chin in the posterior abdomen (video: https://short-link.me/-MNT). Referring to it as a DRS block may be a misnomer; the term ‘midline/anterior TF plane block’ is a more anatomically accurate description.

The authors suggested that the DRS block may influence autonomic fibres by spreading posteriorly along the TF towards the retroperitoneal space and potentially reaching sympathetic structures.[1] However, achieving visceral analgesia typically requires direct or near-direct blockade of autonomic afferents, such as the splanchnic nerves or the celiac plexus, which are anatomically distant and well-protected by retroperitoneal tissues.[9] A 20-mL volume, as used in this case, is unlikely to achieve sufficient spread to these anatomically distant autonomic targets. Clinically meaningful visceral and somatic analgesia, as required for procedures such as laparoscopic cholecystectomy, is more reliably achieved through LA spread to the thoracic paravertebral space, where both intercostal and sympathetic fibres can be effectively blocked.[10] The fascial continuity cited by the authors is insufficient to guarantee such spread, particularly in the absence of radiological or cadaveric confirmation.

Conflicts of interest

There are no conflicts of interest.

Disclosure of use of artificial intelligence (AI)-assistive or generative tools

The authors confirm that no AI tools or language models (LLMs) were used in the writing or editing of the manuscript, and no images were manipulated using AI.

Authors contributions

KS: Concepts, Design, manuscript preparation, review, and approval. NRN: literature search, manuscript preparation, review, and approval. TM: Concepts, Design, Definition of intellectual content, literature search, manuscript preparation, editing, review, Schematic drawing, and photo editing.

Presentation at conferences/CMEs and abstract publication

Nil.

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Funding Statement

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