Ultrasound-guided Rectus Sheath Block
- Dr Arul James, MD, FRCA, FFPMRCA test
- Apr 11
- 4 min read
Rectus Sheath Block – ARiRA Pro Tips
Indications
The rectus sheath block is a focused regional anaesthesia technique used to provide somatic analgesia to the anterior abdominal wall. It is particularly beneficial for:
Midline laparotomies
Umbilical hernia repair
Paraumbilical laparoscopic port sites
Paediatric abdominal wall procedures
Incisional pain management following general or spinal anaesthesia
This block targets the terminal branches of the intercostal nerves (T7–T12) before they perforate the rectus sheath.
Anatomy
The rectus abdominis muscle lies within the rectus sheath, which consists of anterior and posterior fascial layers. The terminal intercostal nerves travel between the posterior rectus sheath and the rectus muscle, providing sensation to the midline abdominal skin. The block is placed into this posterior fascial plane, allowing it to spread along the sheath and cover multiple segments.
Patient Positioning
Position the patient supine with arms by the side. A slight bend at the hips or knees may help relax the abdominal wall. Ensure full access to the lower thoracic and upper abdominal region. This position facilitates comfortable probe handling and needle manipulation.
Ultrasound Technique
Probe Placement:
Begin by placing the high-frequency linear probe transversely on the midline of the abdominal wall, directly over the linea alba, which appears as a bright, hyperechoic line separating the paired rectus abdominis muscles. This acts as the starting reference point. Then, slide the probe laterally, approximately 2–5 cm from the midline, near the level of the umbilicus, until the rectus abdominis muscle and its surrounding rectus sheath come into view.
Landmarks:
The rectus abdominis muscle appears as a thick, hypoechoic structure, enclosed by hyperechoic layers — the anterior and posterior rectus sheaths. The posterior rectus sheath is the critical target landmark, as the injection is made between this layer and the rectus muscle, where the intercostal nerves (T7–T12) travel.
Orientation:
Keep the probe in a transverse orientation to obtain a cross-sectional view. This visualises:
The rectus abdominis centrally
Posterior sheath deep to the muscle
The peritoneum, as a shimmering structure below, which must be avoided
Optimise depth, gain, and focal zones to enhance fascial plane resolution, ensuring safe and accurate needle guidance into the correct interfascial space.
Needle Insertion
An in-plane technique is preferred. The needle is introduced from lateral to medial, aiming to enter the plane between the posterior rectus sheath and the rectus muscle. Hydrodissection with saline confirms the correct space. The needle should remain superficial to the peritoneum at all times to avoid intraperitoneal injury. Avoid an out-of-plane approach unless access is limited, as visualisation of the tip becomes challenging.
Injection Volume
Adults: 10–20 mL of local anaesthetic per side
Bilateral injections are often required for midline incisions
Inject slowly while observing spread within the fascial plane
Use colour Doppler to identify and avoid epigastric vessels
Maximising Block Effectiveness
Confirm correct placement using hydrodissection – the muscle should lift off the posterior sheath.
Maintain continuous needle visualisation throughout insertion
Use a short bevel echogenic needle to enhance precision
Target the segment closest to the surgical site, typically near the umbilicus, for best spread
Minimising Complications
The rectus sheath block is generally safe when performed under direct ultrasound guidance, but care is required to avoid:
Peritoneal puncture: Always maintain needle above the posterior sheath
Epigastric vessel injury: Use Doppler before injection
Local Anaesthetic Systemic Toxicity (LAST): Aspirate before injecting, use incremental dosing (3–5 mL at a time), and calculate total dose based on weight
Poor spread: Confirm muscle lift-off from the posterior sheath during injection to ensure correct plane and adequate spread.
Rectus Sheath Block – Frequently Asked Questions
What is the primary purpose of a rectus sheath block?
It provides somatic analgesia to the anterior abdominal wall, particularly effective for midline incisions such as those in umbilical hernia repairs and laparotomies.
Which nerves are targeted during this block?
The anterior cutaneous branches of the lower thoracic intercostal nerves (T7–T12) as they traverse the posterior rectus sheath.
Is the block suitable for all abdominal surgeries?
It's most effective for midline procedures. For lateral or visceral pain, alternative blocks like the transversus abdominis plane (TAP) block or quadratus lumborum (QL) block may be more appropriate.
How much local anaesthetic should be administered?
Typically, 10–15 mL per side in adults. The volume may vary based on patient size and surgical extent.
Is bilateral administration necessary?
Yes, for midline incisions to ensure comprehensive analgesia.
What are the key anatomical landmarks?
The rectus abdominis muscle and its posterior sheath, identified using a high-frequency linear ultrasound probe placed transversely near the umbilicus.
What are common complications?
Potential risks include peritoneal puncture, bowel injury, or vascular puncture. Utilising ultrasound guidance mitigates these risks.
How can I confirm correct needle placement?
By observing hydrodissection between the rectus muscle and posterior sheath during a test injection.
Is this block effective for visceral pain?
No, it primarily addresses somatic pain. Visceral analgesia requires different techniques.
Can this block be used in paediatric patients?
Yes, with adjusted volumes. For instance, 0.25 mL/kg per side of 0.25% levobupivacaine is commonly used for rectus sheath block in children undergoing umbilical hernia repair, ensuring the total dose does not exceed 2 mg/kg.
Are there any contraindications?
Local infection at the injection site, allergy to local anaesthetics, or coagulopathy are contraindications.
How does this block compare to TAP blocks?
While both target abdominal wall analgesia, the rectus sheath block is more focused on the midline, whereas TAP blocks cover lateral abdominal regions.
Can continuous analgesia be achieved with this block?
Yes, placing catheters within the rectus sheath for continuous infusion is beneficial for extended postoperative pain control.
What is the duration of analgesia?
Depends on the local anaesthetic used. For example, 0.25% levobupivacaine typically provides 6–12 hours of relief.
Is this block suitable for obese patients?
Yes, but increased depth may require adjustments in ultrasound settings and needle length.
How can I enhance my proficiency in this technique?
Engage with platforms offering virtual simulations and detailed anatomical guides to practice and refine your skills like https://www.arira.co.uk.
This content has been specifically tailored for healthcare professionals, focusing on unique strategies to optimise safety and efficacy during rectus sheath block procedures. Always apply clinical judgment tailored to individual patient needs.
