Ultrasound Blocks for the Anterior Abdominal Wall
Ultrasound Blocks for the Anterior Abdominal Wall
Ultrasound Blocks for the Anterior Abdominal Wall
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18 | <strong>Ultrasound</strong> <strong>Blocks</strong> <strong>for</strong> <strong>the</strong> <strong>Anterior</strong> <strong>Abdominal</strong> <strong>Wall</strong><br />
intercostal plexus. The nerves from T9 to L1 contribute to a<br />
longitudinal nerve plexus, named <strong>the</strong> transverse abdominal<br />
muscle plexus, that lies alongside and lateral to <strong>the</strong> ascending<br />
branch of <strong>the</strong> deep circumflex iliac artery (Rozen 2008).<br />
The nerves from T6 to L1 <strong>for</strong>m a fur<strong>the</strong>r plexus into <strong>the</strong> rectus<br />
sheath named <strong>the</strong> rectus sheath plexus. This plexus runs<br />
cranial-caudally and laterally to <strong>the</strong> lateral branch of <strong>the</strong> deep<br />
inferior epigastric artery (Rozen 2008). A branch of T10<br />
innervates <strong>the</strong> umbilicus.<br />
Iliohypogastric and Ilioinguinal Nerves<br />
The lumbar plexus, <strong>for</strong>med by <strong>the</strong> ventral branches of <strong>the</strong><br />
spinal nerves from L1 to L4, projects laterally and caudally from<br />
<strong>the</strong> intervertebral <strong>for</strong>amina. Its roots innervate <strong>the</strong> lower part of<br />
<strong>the</strong> anterior abdominal wall, <strong>the</strong> inguinal field, through <strong>the</strong><br />
iliohypogastric nerve (IHN-greater abdominogenital nerve), <strong>the</strong><br />
ilioinguinal nerve (IIN-minor abdominogenital nerve) and <strong>the</strong><br />
genitofemoral nerve (GFN) (Horowitz 1939).<br />
A communication branch from T12 that is called <strong>the</strong> subcostal<br />
nerve may join in 50 to 60% of cases <strong>the</strong> anterior primary<br />
division of L1. More rarely a branch of T11 may also join L1.<br />
The IIH and IIN pass obliquely through or behind <strong>the</strong> psoas<br />
major muscle and emerge from <strong>the</strong> upper lateral border of <strong>the</strong><br />
psoas major muscle at <strong>the</strong> L2 to L3 level (Mirilas 2010). The IHN<br />
nerve, <strong>the</strong> first of <strong>the</strong> lumbar plexus, and <strong>the</strong> IIN may be found as<br />
a single or divided trunk in <strong>the</strong> retroperitoneal space. They cross<br />
obliquely parallel to <strong>the</strong> intercostal nerves and behind <strong>the</strong> lower<br />
pole of <strong>the</strong> kidney towards <strong>the</strong> iliac crest (which explains <strong>the</strong><br />
referred pain to genitalia in kidney and ureter affections)<br />
(Anloague 2009).<br />
Above <strong>the</strong> iliac crest, <strong>the</strong> IHN and IIN pierce <strong>the</strong> posterior<br />
surface of <strong>the</strong> TAM and run between this muscle and <strong>the</strong> IOM<br />
toward <strong>the</strong> inguinal region (Jamieson 1952, Mirilas 2010).