Ultrasound-guided anterior celiac plexus block is utilized in a variety of clinical scenarios as a diagnostic and therapeutic maneuver. As a diagnostic tool, ultrasound-guided anterior celiac plexus block aids in the differential diagnosis of abdominal pain helping determine whether flank, retroperitoneal, or upper abdominal pain is sympathetically mediated via the celiac plexus. Prognostically, this technique may be used to determine if celiac plexus neurolysis will in fact provide pain relief for pain thought to be mediated via the celiac plexus. Early use of ultrasound-guided anterior celiac plexus block to deliver local anesthetic and steroid is not only efficacious in the relief of pain secondary to acute pancreatitis but can markedly reduce the morbidity and mortality associated with this disease. This technique also has utility in the management of abdominal angina and may aid in bowel preservation in patients suffering from ischemic bowel. Ultrasoundguided anterior celiac plexus block can also be utilized to provide acute pain management for arterial embolization of the liver procedures to treat liver tumors. Destruction of the celiac plexus with alcohol and phenol using ultrasoundguided anterior celiac plexus block is a mainstay of cancer pain management when treating pain secondary to malignancies of the retroperitoneum including pancreatic cancer and can be utilized in selected patients suffering from chronic nonmalignant abdominal pain syndromes including chronic pancreatitis (Fig. 98.1).

Advantages of the ultrasound-guided anterior approach to celiac plexus block over traditional posterior approaches include its ease and speed of performance; the lack of radiation associated with fluoroscopic or computed tomography (CT) techniques; the ability to perform the procedure with the patient in the supine position, sparing the patient the need to remain in the prone position for prolonged periods of time or to lie on colostomies or ileostomies; the lack of periprocedure pain due to the fact that the needle does not have to pass through the major muscles of posture; and the fact that the needle is placed in the precrural space, avoiding the possibility of trauma to exiting nerve roots or inadvertent injection of the epidural, subdural, or subarachnoid space due to retrocrural spread of injectate (Table 98.1).

The sympathetic innervation of the abdominal viscera originates in the anterolateral horn of the spinal cord (Fig. 98.2). Preganglionic fibers from T5 to T12 exit the spinal cord in conjunction with the ventral roots to join the white communicating rami on their way to the sympathetic chain. Rather than synapsing with the sympathetic chain, these preganglionic fibers pass through it to ultimately synapse on the celiac ganglia. The greater, lesser, and least splanchnic nerves provide the major preganglionic contribution to the celiac plexus. The greater splanchnic nerve has its origin from the T5-T10 spinal roots. The nerve travels along the thoracic paravertebral border through the crus of the diaphragm into the abdominal cavity, ending on the celiac ganglion of its respective side. The lesser splanchnic nerve arises from the T10-T11 roots and passes with the greater nerve to end at the celiac ganglion. The least splanchnic nerve arises from the T11-T12 spinal roots and passes through the diaphragm to the celiac ganglion.

There is significant interpatient anatomic variability of the celiac ganglia with the number of ganglia varying from one to five and ranging in diameter from 0.5 to 4.5 cm. The ganglia lie anterior and anterolateral to the aorta at the level of the celiac trunk (Fig. 98.3). In most patients, the ganglia located on the left are uniformly more inferior than their right-sided counterparts by as much as a vertebral level, but both groups of ganglia usually lie approximately at the level of the upper first lumbar vertebra.

Postganglionic fibers radiate from the celiac ganglia to follow the course of the blood vessels to innervate the abdominal viscera. These organs include much of the distal esophagus, stomach, duodenum, small intestine, ascending and proximal transverse colon, adrenal glands, pancreas, spleen, liver, and biliary system. It is these postganglionic fibers, the fibers arising from the preganglionic splanchnic nerves, and the celiac ganglion that make up the celiac plexus. The diaphragm separates the thorax from the abdominal cavity while still permitting the passage of the thoracoabdominal structures, including the aorta, vena cava, and splanchnic nerves. The diaphragmatic crura are bilateral structures that arise from the anterolateral surfaces of the upper two or three lumbar vertebrae and discs. The crura of the diaphragm serve as a barrier to effectively separate the splanchnic nerves from the celiac ganglia and plexus below.

The celiac plexus is anterior (precrural) to the crus of the diaphragm. The plexus extends in front of and around the aorta, with the greatest concentration of fibers anterior to the aorta at the level of the celiac truck, which along with the aorta provides the clinician with an easily identifiable sonographic landmark when performing this technique (Fig. 98.4). With the ultrasound-guided anterior approach to celiac plexus block, the needle is placed close to this concentration of plexus fibers. The relationship of the celiac plexus to the surrounding structures is as follows: the aorta lies anterior and slightly to the left of the anterior margin of the vertebral body (Fig. 98.5). The inferior vena cava lies to the right, with the kidneys posterolateral to the great vessels. The pancreas lies anterior to the celiac plexus. All of these structures lie within the retroperitoneal space. With the anterior approach, the needle may traverse the liver, stomach, intestine, vessels, and pancreas.