The "single-needle" celiac plexus block is becoming a popular technique. Despite different approaches and methods used to place the needle, the success of the block depends on adequate spread of the injectate in the celiac area. In the present retrospective study, the influence of needle tip position in relation to the celiac artery on injectate spread was evaluated.
Among 138 cancer patients subjected, via an anterior approach, to computed tomography (CT)-guided single-needle neurolytic celiac plexus block, a radiologist, blinded to the aim of the study, retrospectively selected 53 cases with normal anatomy of the celiac area as judged by CT. The decision was based on images obtained before the block. Patients were then classified into either group A (29 patients), in whom the needle tip was caudad to the celiac artery, and group B (24 patients), in whom it was cephalad. To evaluate CT patterns of neurolytic (mixed with contrast) spread, the celiac area was divided on the frontal plane into four quadrants: upper right and left and lower right and left, as related to the celiac artery. Patient assessments by visual analog scale were reviewed to evaluate the degree of pain relief. Pain relief 30 days after block was judged as long-lasting. The patterns of contrast spread in relation to the needle position and pain relief according to the number of quadrants with contrast were analyzed.
The percentage of cases with four quadrants with contrast was higher when the needle tip was cephalad (58%, group B) than when it was caudad (14%, group A) to the celiac artery (P < 0.01). The percentage of patients with four and three quadrants with contrast was also higher in group B at 79% than in group A at 38% (P < 0.01). A significant difference in long-lasting pain relief was observed between patients with four quadrants with contrast (18 of 18, 100%; 95% confidence interval [CI], 81-100%) and patients with three quadrants with contrast (5 of 12, 42%; 95% CI, 15-72%) (P < 0.01). No patients showing two or one quadrant with contrast had long-lasting pain relief.
These findings suggest that, when the celiac area is free from anatomic distortions, and the single-needle neurolytic celiac plexus block technique is used, the needle tip should be positioned cephalad to the celiac artery to achieve a wider neurolytic spread. It also appears that only a complete (four quadrants) neurolytic spread in the celiac area can guarantee long-lasting analgesia.
Pain impulses originating from all the abdominal and most pelvic viscera (pancreas, liver, stomach, intestine proximal to transverse colon, renal pelvis, ureter, and gallbladder) are carried by visceral nerve fibers that pass through the celiac plexus and splanchnic nerves. Interruption of nociceptive input at the level of either the celiac plexus or the splanchnic nerves therefore is a potentially effective means of visceral pain control. 
Several techniques of anesthetic and neurolytic blocks of the celiac plexus are used. In the anterior approach, in which the patient is supine, the block is performed using a single fine biopsy needle, mainly under computed tomographic (CT)[2–5] or sonographic [6–8] guidance. According to some authors, the position of the single needle at the level of the celiac artery is irrelevant, because injected liquids spread extensively in the preaortic soft tissues.  However, as acknowledged by several authors, [3,10–12] despite the correct needle position, injectate spread in the celiac area is often hampered by regional anatomic distortion due to tumor or previous therapy. The specific aim of this retrospective study was to evaluate the role of the position of a single needle in relation to the celiac artery in determining the patterns of injectate spread in patients with no apparent anatomic distortion of the celiac area, as judged by CT. The patterns of injectate spread in relation to the needle position and analgesic results according to the different patterns of injectate spread are analyzed and discussed.
Materials and Methods
In a 5-yr period, between 1989 and 1994, 138 cancer patients being treated at our institute underwent CT-guided, single-needle neurolytic celiac plexus block for upper abdominal pain regarded as of celiac ganglion origin, for which pharmacologic treatment proved either ineffective or limited by side effects. The hospital charts of these patients were reviewed, and a radiologist, blinded to the aim of the study, retrospectively selected 53 patients whose celiac area was apparently free from alterations related to either tumor or therapy, as judged by CT. The decision was based on images obtained before the block. Patients were subsequently assigned to one of two groups based on the position of the needle tip during the celiac block procedure: In group A (29 patients), CT scans showed the needle tip between the celiac and the superior mesenteric arteries closer to the anterior wall (on midline or just lateral) of the aorta; in group B (24 patients), the needle tip was just cephalad (19 cases) or lateral (5 cases) to the root of the celiac artery. Preblock patient characteristics, diseases, and therapy are shown in Table 1.
The technique of celiac plexus block used was as follows: All of the patients had been fasting for at least 12 h before the procedure and had normal coagulation values; 15 ml/kg saline and 0.15 mg/kg diazepam were infused before the procedure via an intravenous cannula, which was kept in place for further medication. The block was performed with the patient supine on the CT table. Preliminary CT scans of thin sections (5 mm thick at 5-mm intervals) were obtained through the upper part of the abdomen, and the celiac and superior mesenteric arteries were identified. The needle tip target was the midline just anterior to the aorta between the roots of the celiac and the superior mesenteric arteries (Figure 1) or just cephalad to the root of the celiac artery (Figure 2); a tip position just lateral to the celiac artery was considered correct. The optimal puncture site and needle path were chosen to avoid, if possible, puncturing the liver, stomach, colon, or pancreas. When organ puncture could not be avoided, the shortest needle path was chosen, and the target (cephalad or caudad to the celiac artery) was established to avoid the puncture of the vessels originating from the celiac artery or the celiac artery itself. The depth from the skin to the ventral wall of the aorta was calculated, and a marker was placed on the skin puncture site. After skin anesthesia, a single 22- or 20-gauge, 15-cm-long Chiba needle was advanced at the predetermined path and depth. If the needle path lead through tumor tissue to reach the target, a 20-gauge needle was preferred because it is subject to less misdirection by solid tumors. If the needle did not follow the path we planned, but one of the previously mentioned targets had been reached, the needle was not repositioned. Once the needle was in the appropriate position, extension tubing was connected, suction was applied, and 2 ml saline were injected to verify that no unexpected resistance to injection was present. If neither bleeding nor abnormal resistance was observed, 2 ml 30% iodinated contrast medium (Ultravist, Schering) mixed with 8 ml 2% lidocaine were injected to rule out inappropriate solution spread (test injection) and to minimize alcohol-induced pain. If the test injection showed a bilateral preaortic spread of the solution, 30 ml ethyl alcohol diluted to 70% with 0.5% bupivacaine, mixed with 2 ml contrast medium, were injected through the extension tubing during a 2-min period. The unilateral preaortic spread of the anesthetic solution was also considered satisfactory because we presumed that the subsequent 30 ml of the neurolytic solution could lead to a wider preaortic spread because the celiac area was free of obvious disease. If the test injection showed inappropriate solution spread (i.e., intraperitoneal or retrocrural), the needle was moved or withdrawn and repositioned until satisfactory spread was obtained, and then the neurolitic solution was injected. Before needle removal, after the extension tubing was detached, 2 ml saline was injected to prevent alcohol from tracking back along the needle path. Immediately after needle withdrawal, serial CT scans of thin sections (5 mm thick at 5-mm intervals) were obtained above and below the injection site up to the lower and upper limits of neurolytic solution spread. During all phases of the block, CT scans were taken.
Evaluation of the alcohol spread was based on the presence of the contrast medium around the anterolateral wall of the aorta, anterior to the crura of the diaphragm, from above the celiac artery to the superior mesenteric artery. To schematize results based on the needle tip position, this area was divided, on the frontal plane, into four nearly equal quadrants: upper right and left and lower right and left, defined by a horizontal line passing just caudad to the root of the celiac artery and by a vertical line at the midline of the ventral wall of the aorta (Figure 3). Results were expressed as the number of quadrants into which the contrast spread; that is, four quadrants with contrast (Figure 2); three quadrants with contrast; two quandrants with contrast, both superior or inferior, or both unilateral, right or left quadrants; and one quadrant with contrast (Figure 1). The differences in contrast spread based on the needle position in relation to the celiac artery were analyzed.
Patient assessments, based on a 0- to 10-cm visual analog scale (VAS), were reviewed to evaluate the degree of pain relief. The VAS was administrated to the patient before and after block. Based on a 10-cm line, the left extremity represented “no pain at all”(score 0) and the right one represented “unbearable pain”(score 10). The distance from score 0 to the point indicated by the patient, rounded off to the nearest whole number of centimeters, expressed the pain score. Because the mean pre-block VAS value was 8 (Table 2), we judged the pain relief after block as good when the score on the VAS was < 5 and poor when it was >or= to 5. Pain relief at 24 h, and at 7 and 30 days after block, according to the number of quadrants with contrast, was analyzed. Pain relief evaluation was completed up until 30 days after block because complete medical records of all the patients were available only until that time. Good pain relief for 30 days after block was judged as long-lasting.
We observed no significant differences between group A and group B patients regarding age, sex, disease, and therapy (Table 1). The patterns of contrast spread, expressed as the number of quadrants with contrast, and differences in contrast spread between group A and group B patients are shown in Figure 4(A and B). The percentage of patients with contrast in four quadrants was higher when the site of injection was cephalad (group B) to the celiac artery than when it was caudad (group A). The percentage of patients with four and three quadrants with contrast was also higher in group B (19 of 24, 79%; 95% confidence interval [CI], 63–95%) than in group A (11 of 29, 38%; 95% CI, 20–56%; P < 0.01). Conversely, the percentage of patients with two and one quadrant with contrast was higher in group A than in group B.
(Table 2) shows VAS pain scores according to the number of quadrants with contrast. Seven and 30 days after block, significant differences in VAS scores, depending on number of quadrants with contrast, were observed. A significant difference in long-lasting pain relief (30 days) was noted between patients with contrast in four quadrants (18 of 18, 100%; 95% CI, 81–100%) and patients with contrast in three quadrants (5 of 12, 42%; 95% CI, 17–72%; P < 0.01). No associations between relative location of the three different quadrants with contrast and pain relief degree were noted (data not shown). No patients with two or one quadrant with contrast experienced long-lasting pain relief. Overall, 24 h after block, good pain relief was observed in 44 of 53 patients (83%); the remaining nine patients with poor pain relief were among those with contrast in only two or one quadrant. Seven days after block, good pain relief was noted in 30 of 53 patients (57%); 22 of the 23 patients with poor pain relief had two or one quadrant with the contrast. Thirty days after block, only 23 of 53 patients (43%) with contrast in four or three quadrants still had good pain relief.
No complications related to the organ puncture, and no neurologic disturbances were observed.
The celiac plexus, the largest of the sympathetic nervous system, is composed of visceral afferent and efferent fibers from the T5 through T12 paravertebral sympathetic ganglia. The vagus nerves contribute to the plexus to a minor extent. The plexus itself consists of a dense network of fibers interconnecting the right and left celiac ganglia. This network encircles the celiac artery and the base of the superior mesenteric artery. After piercing the crus of the diaphragm, sympathetic fibers from the right and left greater and lesser splanchnic nerves end in the celiac ganglia.  Normal anatomic variations of the celiac ganglia (number and location) were described in 1979 by Ward et al.,  who emphasized that the celiac artery is the most reliable landmark nearby for locating the celiac plexus.
Anesthetic or neurolytic blocks of the splanchnic nerve, celiac plexus, or both are commonly used procedures to control pain due to interventional biliary procedures, [16,17] benign chronic abdominal processes, and primary or metastatic cancer of the upper abdominal viscera. [1,18]
Since 1919, when Kappis  first described percutaneous splanchnic nerve anesthesia, various techniques of anesthetic and neurolytic blocks of the celiac plexus have been introduced. Retrocrural bilateral splanchnic nerve block by a posterior approach has been used most widely. [20,21] In the past decade, some authors have emphasized the transcrural or transaortic technique for injecting a neurolytic agent directly on or into the celiac plexus, thus avoiding the risk of neurologic complications due to retrocrural and psoas compartment involvement. [10,22,23]
Because of the anatomic variations of the celiac plexus in relation to the vertebral column (from the bottom of T12 to the middle of L2) and its more consistent relation with the celiac artery, CT is considered the best imaging technique to document a correct needle tip position.  Furthermore, CT scanning is useful to define the retroperitoneal anatomy (the anatomic relation of the retroperitoneal organs is often distorted by tumor or previous operations), in determining the best route for needle insertion, in avoiding organ puncture, and in documenting the contrast spread, which may be irregular despite the correct needle position. 
More recently, the anterior approach to the celiac plexus block under CT [2–5] or sonographic [6–8] guidance has been suggested. This approach would offer several advantages over the posterior approach, including shorter procedure time, less discomfort to the patient, use in patients who cannot tolerate the prone position, and a reduced risk of neurologic complications. The major disadvantage of this approach is possible perforation of the stomach, intestine, liver, or pancreas. Nevertheless, fine-needle pancreas biopsy, which is nearly the same procedure and performed in thousands of patients, has a very low complication rate. [24–26]
Although some authors  believe that only a bilateral injection in the prone patient will yield optimal results, several investigators report similar results when injection is performed with a single needle with the patient lying prone [9,10,27] or supine. [2–8] Despite many attempts to get better analgesia by trying to locate the optimal needle position to improve the spread of the injectate to the plexus area, published data have not shown a clear advantage of any of these techniques.  Nevertheless, whichever technique is used, the success of a celiac plexus block (excluding the retrocrural splanchnic nerve block) depends on the adequate spread of the injectate in the celiac area. Furthermore, failures are common to any technique due to regional infiltration by cancer tissue, anatomy disruption by either previous surgery or radiation therapy, or insufficient volume of the injected agent.
Authors who have used the single-needle procedure under CT or sonographic guidance positioned the needle tip cephalad [2,6] at the level of [8,9] or caudad [4,5,7] to the celiac artery, and all achieved a high success rate, suggesting an adequate spread of the injectate in the celiac area. Furthermore, some authors state that “the exact level” of the needle tip in relation to the celiac artery “is not critical because injected liquids spread extensively in the preaortic soft tissues.” Our data show that when the needle tip was positioned caudad to the celiac artery, between the celiac and the superior mesenteric arteries (group A), the neurolytic solution spread extensively (four quadrants with contrast) in a low percentage of patients (14%). With the needle tip cephalad to the celiac artery (group B), four quadrants with contrast occurred in more of the cases (58%). In addition, the percentage of patients with four and three quadrants with contrast was higher in group B (79%) than in group A (38%). Because the celiac area was free from anatomic alterations in all patients, we believe that the role of the needle tip position in relation to the celiac artery cannot be disregarded. Furthermore, due to the similar anatomic and clinical conditions in both groups, common factors influencing the distribution of fluids in the body, such as texture and grain of the tissues, pressure imposed by adjacent organs that can direct fluids to low-pressure areas, and also gravity, are not sufficient to justify the different patterns of contrast spread observed. Furthermore, when the needle was cephalad to the celiac artery, the contrast spread in the two upper quadrants in all but two patients (92%), whereas when the needle was positioned caudad to the celiac artery, the contrast spread in the two lower quadrants in only 17% of the patients. These findings lead to the hypothesis, previously suggested by Roussiel and Walther,  that an obstacle, possibly due to a more dense texture of the preaortic tissues not detectable by CT, could hamper the bilateral spread of the injected solution caudad to the celiac artery. Obviously, this hypothesis needs to be confirmed by cadaver studies, other clinical studies, or both.
As far as pain relief according to the number of quadrants with contrast is concerned, our results clearly show that only the complete spread (four quadrants with contrast) of the neurolytic solution in the celiac area ensures long-lasting pain relief. In fact, despite needle position, all patients with contrast in four quadrants experienced long-lasting pain relief. Among 12 patients with three quadrants with contrast, only five (42%) obtained long-lasting pain relief. Because no association between the three different quadrants of contrast spread and pain relief degree was observed, it is not possible to determine if a side of the celiac plexus, not blocked adequately, could result in poor clinical outcome. Therefore, our data suggest that when a large part, but not all, of the celiac area is reached by the neurolytic solution, only a minor percentage of patients will experience long-lasting pain relief. Furthermore, when the neurolytic spread constitutes only one part, either right or left, superior or inferior, of the celiac area, poor pain relief should be expected.
Altogether, pain relief was better in the patients with contrast in four quadrants than in those with three, two, or one quadrant. This difference was not observed 24 h after block (Table 2), suggesting that early pain relief evaluation overestimates the effectiveness of the neurolytic block.
Although our data demonstrated that needle placement cephalad to the celiac artery leads to wider spread of the injected solution, it should be emphasized that in some patients an incomplete spread of the injected solution may occur, even when the celiac area appears free from regional anatomic distortion. Because the neurolytic celiac plexus block is mainly performed to control pain related to pancreatic cancer, which at the time of presentation had already metastasized in more than 50% of the patients,  it is unlikely that the celiac area could be free from alterations due to cancer, previous surgery, or radiation therapy-induced fibrosis. In such patients, therefore, complete spread of the neurolytic agent may be more difficult to achieve than in our selected patients, regardless of the technique used. In 85 of 138 patients subjected to single-needle neurolytic celiac plexus block, who were not included in this study because their celiac area was infiltrated or compressed by tumor, distorted by previous surgery or radiation therapy, or both, the spread of the neurolytic solution was always clearly influenced by the regional anatomic distortions, regardless of the needle position in relation to the celiac artery. Four, three, two, or one quadrant with contrast were observed in 9%, 18%, 49%, and 24% of the patients, respectively. Overall, long-lasting pain relief occurred in only 17 (eight with four quadrants with contrast, nine with three quadrants with contrast) of the 85 patients (20%).
As in other interventional procedures, the choice of the technique for celiac block depends on the operator's preferences. We believe that it must also be based on the anatomic conditions of the celiac area in each patient to obtain the best results. When the celiac area is free from anatomic alterations and a single-needle precrural approach is chosen, the needle tip position in relation to the celiac artery becomes critical. The data of the present study suggest that the site of injection should be cephalad to the celiac artery to obtain a wider spread of the injected solution. Only a complete spread of the neurolytic solution in the celiac area seems to guarantee long-lasting analgesia.
The authors thank Cinzia Ros for secretarial assistance.