Celiac plexus block: an anatomical study and simulation using computed tomography (2024)

Language: English | Portuguese

Abstract

Keywords: Celiac plexus block, Transcrural pathway, Computed tomography, Anatomy

Abstract

INTRODUCTION

Celiac plexus block (CPB) is prescribed in cases of upper abdomen cancer, chronicpancreatitis, metastases, painful retroperitoneal tumors and chronic abdominal pain inpatients who do not respond to treatment regimens based on high-dose narcoticanalgesia^(1-3). Since the beginning of the 20th century, the CPBtechnique has been adapted, giving rise to a variety of techniques that differ mainly inthe type of access, the instruments used, sedation, neurolytic solutions, imagingguidance and timing in the course of the disease. The variations and combinations oftechniques stand as a means to increase the chances of success in the procedure as wellas to reduce the occurrence of complications and morbidity^(4-8).

The celiac plexus (CP) is deeply located in the retroperitoneum, overlying theanterolateral surface of the aorta, at the level of the celiac trunk (CeT), comprising adense network of ganglia that varies considerably in size, number andpositioning^(6-13). It originates from sympathetic fibers of splanchnicnerves, extending from T5 to T12, and containing preganglionic splanchnic afferentfibers, preganglionic parasympathetic fibers and postganglionic sympathetic fibers. TheCP is found in the epigastrium, posteriorly to the stomach and the pancreas, andanteriorly to the diaphragmatic pillars, where it surrounds the CeT, the superiormesenteric arteries and the aorta. The visceral pain transmitted by the CP is related tothe pancreas, diaphragm, stomach, liver, spleen, small bowel, transverse colon,suprarenal glands, kidneys, abdominal aorta and mesenterium^(7,13,14).

The retrocrural, transcrural, transaortic and anterior approaches are the most commonlyutilized in CPB, differing from each other in needle directioning, insertion angulationand pathway, as well as in patient positioning, among other factors that involve risksand benefits peculiar to each technique. In CPB, the imaging guidance utilized tovisualize the correct insertion of the needle and to confirm contrast medium spread ismost commonly done with either computed tomography (CT), ultrasonography orfluoroscopy^{(6-8,12,15-18)}. The decisionon which individual technique to adopt should be based on the available facilities,clinical expertise, the patients' physical condition, and on the diseaseseverity⁽¹⁸⁾.

CPB may pose risks to the patient, depending on the technique employed and on abdominalanatomical variations⁽¹⁹⁾. Althoughcomplications have been recorded in less than 2% of patients submitted to CPB,diaphragmatic irritation, orthostatic hypotension, pneumothorax, pericarditis,intervertebral disc injury, retroperitoneal abscess, transient diarrhea, arterydissection, pleuritis and neurologic damage have been reported^(8,17). In spite of that, reports in the literature confirm thesignificant benefits to the quality of life of patients who undergo thisprocedure^{(4,17,18,20,21)}.

The variation in CPB techniques adopted since 1919⁽³⁾ and the scarcity of studies reporting problems after thisprocedure such as organ transfixion and neurologic injury, or even discussing theanatomical variations of structures involved in CPB unveil the need for furtherinformation regarding this relevant analgesic resource.

The present study was aimed at analyzing the anatomical variations of structuresinvolved in CPB and implementing one of the techniques described in the literature bymeans of simulations utilizing CT. Axial CT sections of the abdomen of adult patientswere analyzed to assess one of the main risks involved in this procedure, i.e., injuryto organs or structures caused by the needle insertion towards the CP region.

MATERIALS AND METHODS

Transaxial contrast-enhanced abdominal CT images (one-centimeter-thick slices) of 108adult patients (72 women and 36 men), recovered from the Siemens Syngo^®system were analyzed. The CPB simulation was based on an adapted version of thetranscrural method⁽²²⁾.

For each patient, an axial section at the level of the CeT was utilized to assess theaorta in the craniocaudal direction, from the diaphragm aortic hiatus to the firstanterior branch of the abdominal aorta. The celiac trunk was identified according to thefollowing criteria: 1) the first anterior branch of the abdominal aorta; 2) divided intoleft gastric artery, common hepatic artery, and splenic artery; 3) different from thesuperior mesenteric artery.

The location of the aorta was determined in relation to the vertebral body at the levelof the CeT emergence, and defined as follows: anterior to the left third (l); anteriorto the middle third (m); and anterior to the right third ® of the vertebral body.

The site of CeT emergence was determined in relation to the vertebral column. As theaxial CT sections were analyzed in the craniocaudal direction, the CeT origin wasidentified taking the aorta as a reference, at the level of either a vertebral body oran intervertebral space, and recorded as follows: at left (L); at the middle (M); atright ® of the aortic wall. The celiac-aortic-vertebral topographic relationship wasanalyzed and divided into the groups L-l, M-m, L-m or M-l, L-r and R-l.

Lines representing the needles pathway were drawn on the axial image where the CeTorigin was identified. From the midline defined as the vertebral spinous process, twolines were drawn on each side of the vertebral body. The original image was rotated 180°so as to simulate the prone position of a patient during the virtual procedure. Thefirst line (L9) was drawn starting 9 cm away from the midline on the skin surface,tangentially to the vertebral body and crossing the diaphragmatic pillars. The secondline was drawn accordingly, though 4.5 cm away from the midline (L4.5). The vital organstransfixed by L9 and L4.5 as well as the correlation between patients' gender and theanalyzed criteria were recorded.

Descriptive statistics were utilized in the data analysis and the data are expressed asmeans ± standard deviation. The CeT emergence sites and their topographic relationshipsare presented as percent values. The exact Fisher test was used to analyze theassociation between patients' gender, CeT emergence site and topographic relationships.The software Bioestat 5.00^® was utilized in the statistical analysis,considering 0.05 as significance level (p ≤ 0.05).

RESULTS

In the present study, CT images of 108 individuals, 72 women and 36 men, were analyzed.Most patients presented normal CT findings. In the cases where alterations weredetected, the following conditions were most commonly diagnosed: renal cyst (12.03%,n = 13); renal lithiasis (8.33%, n = 9); hepaticcyst (5.55%%, n = 6); liver metastasis (4.6%, n = 5);colon diverticula (3.7%, n = 4); hepatic nodules (2.77%,n = 3); and retroperitoneal lymph node enlargement (2.77%,n = 3). Renal carcinoma and hepatocellular carcinoma were alsodiagnosed.

As regards CeT emergence site in relation to the vertebra, in 36.11% of the cases itemerged at the level of T12; in 32.4%, between T12 and L1; in 27.77%, at the level ofL1; and only in 2.77%, between T11 and T12.

The results regarding celiac-aortic-vertebral topographic relationship showedcorrespondence at the left aortic wall (L-l) in 22.22% of cases, at the middle (M-m) in23.15%, at the left-middle (L-m) in 31.48%, and central-left (M-l) in 23.15% of cases.No correspondence at the right side of the aortic wall was observed.

The percentages of organs transfixed by lines L9 and L4.5 are demonstrated on Table 1. Table2 shows the results regarding organ transfixion by L9 and L4.5 describing aneedle's pathway observed in the present study and in the study developed by Yang etal.⁽²²⁾. Images of sometransfixed organs are shown on Figure 1.

No significant correlation was observed between genders and celiac-vertebral,aortic-vertebral, celiac-aortic and celiac-aortic-vertebral topographicrelationships.

DISCUSSION

Scarce information is found in the literature on the radiographic anatomy of structuresinvolved in CPB. The anatomical variations in the CeT and adjacent structures in theabdomen, which play an essential role in the guidance of the needle during blockprocedures have not been duly investigated^(5,22).

As regards the celiac-aortic-vertebral topographic relationship, Yang et al. havereported twice as many cases as compared with the present study, particularly for theL-l group⁽²²⁾. The present results donot reveal any correlation on the right side, which is corroborated by the low frequencyreported in the mentioned study (0.5% for both L-r and R-l).

The data of the present study regarding the site of CeT emergence from the aorta aresimilar to those reported by Yang et al.⁽²²⁾. On the other hand, as regards celiac-vertebral topographicrelationship, Yang et al. have observed CeT emergence site between T11-and T12 in 6.5%of cases, as compared with only 2.77% observed in the present study.

Data about gender-related associations reported by Puelma et al.⁽²³⁾ demonstrate correlation with T12 in 50%of male and in 52,9% of the female patients, and with L1 in 50% and 47.1%respectively.

A significant difference in the aortic-vertebral topographic relationship was observedas the data from de present study are compared with those reported by Yang etal.⁽²²⁾, who reported 70%anterior to the left third, 29% anterior to the middle third, and 1% anterior to theright third of the vertebral body.

The risk for organ injury by needles in CPB according to two lines drawn from themidline was analyzed. In the present study, the right and left lungs were transfixed bythe needle pathways corresponding to both lines (Figure1), while the results reported by Yang et al.⁽²²⁾ did not reveal any possibility of pneumothorax.Additionally, results regarding injury to kidneys, inferior vena cava, aorta and liverwere also very different from those reported by the mentioned study (Table 2). Such differences observed between the twostudies clearly reveal the key role played by anatomical variations in CPB.

Kidney transfixion is most likely to occur as the needles are inserted < 7.5 cm awayfrom the midline and as they run laterally to the vertebral body⁽⁶⁾. Injury to the pancreas, stomach andliver as well as pneumothorax are rarely reported in the literature^{(5,7,17,24,25)}. Injury to kidneys andlungs, for example, has never exceeded 0.8%⁽²⁴⁾. The imaging guidance with CT may minimize the occurrence ofsuch complications⁽⁶⁾.

In an effort to simulate new needle pathways to the CP to avoid organs injury, 7.5% ofthe 400 simulations on images were excluded from the study because of the occurrence oforgan transfixion⁽²⁶⁾. The same studyreported difference in the distance between the site where needles were inserted and themidline (IP-ML) in men and women; larger distances were observed in men. Significantdifferences were also observed between the right side (7.04 cm) and the left side (3.58cm) for this criterion. A distance of about 7.5 cm was suggested for both sides, thoughit might vary between 4 cm and 10 cm⁽²⁷⁾.

The IP-ML distance in male patients with pancreatitis was larger (7.47 cm on the rightside and 3.78 on the left side), as compared with female patients with the samecondition (6.64 cm on the right and 3.25 cm on the left side)^(22,26). In thepresent study, the diseases detected on images did not have any influence on anatomicalaspects and therefore no change was required in the needle pathway up to the CP.

In the literature approaching CPB, there are scarce data about abdominal anatomicalvariations in men and women, which has been reported in a study developed by McCartneyet al.⁽⁵⁾. In the present study, nocorrelation was observed between gender and CeT-vertebral, aortic-vertebral, CeT-aorticand celiac-aortic-vertebral topographic relationships. Similarly, data previouslypublished on the CeT-vertebral topographic relationship were not significant⁽²³⁾.

There is controversy about the most appropriate imaging method for guidance inCPB^(3,5,6,18). In another study, Yang et al. recommend the use ofpreprocedural CT images and fluoroscopy during the procedure⁽²⁸⁾. Other authors understand that CT-guidance is moreappropriate both previously and during the procedure, considering that risks areconsiderably reduced with the use of this method^{(7,8,17,25,29,30)}.

CONCLUSION

CPB should not be standardized, considering the wide range of gender-related abdominalanatomical variations, laterality and pathologies, as well as the characteristics ofneedle insertion pathways. Imaging should be performed prior to the procedure in orderto reduce the risks for injuries or for negative outcomes to patients.

Gender-related anatomical variations of structures involved in celiac plexus blockshould be more deeply investigated, since few studies have addressed the subject.

The present study may contribute for the knowledge on the anatomy of abdominal arteriesrequired in other invasive surgical, diagnostic or therapeutic procedures.

Footnotes

REFERENCES