INTRODUCTION

Celiac trunk (CTR) is the major ventral vessel arising from the abdominal aorta (AA) at the level of T12, gives branches including the left gastric artery (LGA), common hepatic artery (CHA) and splenic artery. CTR with the superior mesentery artery (SMA) supplies the majority part of gastrointestinal tract and abdominal viscera^1-3. SMA is the second major ventral branch of AA arising at the level of L1 and running down in front of the third part of the duodenum, and it supplies the small intestine.

Many variation forms of these arteries have been reported in several studies^4-7. The Celiac mesenteric trunk (CMT), which comprises CTR and SMA, is the rarest arterial variation with the reported prevalence of 0.46-3.06%^7-12. Determination and demonstration of these variations is highly important to detect the underlying pathology of CMT such as thrombosis-occlusion^13,14 or stenosis^13,15,16 and to prevent any undesirable complications and fatal outcomes prior to surgical and interventional vascular procedures^17-19. Cross-sectional modalities such as computed tomography (CT) play an essential role in the diagnosis. CT is easy to apply, rapid, non-invasive imaging method with an excellent spatial and temporal resolution.

The aim of this study is to define the morphometric results of the rare CMT variation using CT images in the light of the literature.

MATERIALS AND METHODS

Study Population

Between February 27, 2017 and March 20, 2020, data of 4,024 patients with any indication and having CT angiographic examinations were scanned from hospital Picture Archive and Communication System by an eight-year experienced radiologist. From this population, 1,919 patients (1,313 males, 606 females; minimum age=18-year-old, maximum=103-year-old, mean age=60.47±14.88 years) with CT angiographic examinations including abdominal vascular structures (CTR, SMA and/or renal arteries) and those with best quality of diagnostic imaging were enrolled in the study and were reviewed retrospectively. CT examinations with poor image quality, non-abdominal CT examinations or those including pathologies affecting vascular structures (any intervention/surgery, stenosis, aneurysm, tumour) were excluded from the study.

A summary of the electronic search in the databases and algorithm of inclusion are shown in Figure 1.

Ethical Statement

This study was approved by the university/local human research ethics committee and all procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.

Tekirdağ Namık Kemal University Local Ethical Committee of the institution approved the study protocol (approval number: 2020.39.02.13)

Data Acquisition

CT acquisitions were performed on 128 row multi-detector CT device (Aquilion™ Prime, Canon Medical Systems).

Scanning Protocol

CT scanning parameters were as follows for each protocol: 100-250 mAs modulated by personal body mass index dose; 100-140 kV tube voltage, 0.5 mm x 80 collimation, 0.35 second gantry rotation time, 0.813 pitch factor, slice thickness 1 mm and slice interval 0.8 mm. For intravenous bolus injection of non-ionic contrast material (350 mg/100 mL, iohexol, Omnipaque®; GE Healthcare, Cork, Ireland), a mechanical injector was used at a flow rate of 4.5-5.0 mL/sec.

CT Image Assessment

An eight-year experienced radiologist retrospectively analysed the CT images and assessed all of the morphometric measurements (diameter, length, angle and orientation classification of CMTs).

CMT Morphologic Analysis

The length, diameter, and vertical and horizontal angles as well as vertical orientation (upward, downward) and horizontal orientation (right or left-sided) were analysed morphologically. The length of CMT was measured from the trunk’s outlet till branching level. Vertical and horizontal angles were measured as the angle between the artery outside border and the horizontal plane line (angle of emergence). CMTs were categorized depending on their locations, orientation and the level of origin from the AA. The diameters of CMTs were measured both on sagittal and coronal planes craniocaudally (Figure 2).

In addition, type classification of CMT cases was evaluated according to the classification by Tang et al.¹¹. CMT was classified into five types:

Type 1: Hepato-gastro-spleno-mesenteric trunk,

Type 2: Hepato-spleno-mesenteric trunk with the LGA arising from the AA,

Type 3: Gastro-spleno-mesenteric trunk with the CHA arising from the AA,

Type 4: Hepato-gastro-mesenteric trunk with the splenic artery arising from the AA,

Type 5: Any other variation that meets the above definition of the CMT (LGA originating from other arteries except the AA, CTR and single common trunk; the CHA arising from the SMA).

Statistical Analysis

Statistical package program (SPSS version 17, Chicago, USA) was used in analysing data. The variables were investigated using visual (histograms, probability plots) and analytical methods to determine whether they were normally or not normally distributed. Investigating the associations between non-normally distributed and/or ordinal variables, the correlation coefficients and their significance were calculated using the Pearson test. Descriptive statistics were used in data analysis. A 5% type 1 error level was used to infer statistical significance.

RESULTS

CMT Cases

Among the patient population having CT angiographic examinations (n=1919), 23 (1.19%) cases were detected to be CMT. Of 23 cases, 20 (87%) were male and three (13%) were female, with the mean age of 57.4±16.62 years (range: 18-83 years).

Morphometric Analysis

The mean length of the CMT was 25.35±9.13 (range: 7.6-38 mm), the mean diameter of CMT was 12.06±2.12 mm (range: 8.5-15.6 mm), the mean vertical and horizontal angles were 18.48±14.16 degrees (range: 0.8-51.3 degrees) and 73.65±10.74 degrees (range: 54-103.4 degrees), respectively.

A negative weak correlation was found between the length and diameter of CMT (p=0.048, r=-0.417) (Figure 3).

In vertical angle assessment of 23 patients, 20 patients (20/23; 87%) had a CMT with a downward orientation and three patients (3/23; 13%) with an upward orientation. Eleven (11/23; 47.8%) of the patients had a CMT with right-sided and 12 (12/23; 52.2%) with a left-sided orientation in horizontal angle assessment.

The mean vertical angle with downward and upward orientations were found as 17±14.28 degrees and 28.56±9.61 degrees, respectively. The mean horizontal angle with right-sided and left-sided orientations were found as 74.44±14.16 degrees and 73±6.88 degrees, respectively.

In CMT population, 15 (65.22%) patients were detected to be type 1 and 8 (34.78%) patients were type 2, respectively (Figure 4). Although there was male preponderance in both of types, type 1 was the most common type in the male population (n=14, 93.3%), while type 2 was the most common in the females (n=2, 25%). Sixty percent (n=9) of type 1 CMT patients tended to have right-sided orientation, while 75% of type 2 CMT patients (n=6) had a tendency of left-sided orientation. In both of types, the majority parts of CMT population (type 1: n=13, 87.6%; type 2: n=7, 87.5%) showed to have downward orientation (Table 1).

The distribution of CMT origin levels was most common in L1-L2 (30.4%, n=7), followed by L1 (26.1%, n=6) and with the same number of patients in T12-L1 and L1- inferior-end-plate level (21.7%, n=5), respectively. The level of origin in type 1 was detected to be most common in L1-L2 level (40%, n=6) and the level of origin in type 2 was mostly at both levels in the L1 and L1-inferior-end-plate (37.5%, n=3). Type 1 was the most dominant type (65.2%, n=6) among all of the levels (T12-L1, L1, L1-inferior- end-plate and L1-L2), while type 2 was dominant only in L1-inferior-end-plate level (60%, n=3). L1-L2 level was the most common level of origin in male population (35%, n=7), while L1 was the most common level in females (66.7%, n=2) (Table 2).

DISCUSSION

In the literature, some studies reported the variations of CTR and CMT with different range of incidence^7-12 and quantitative measurements (length, diameter, type and level of origin, angle)^8,11,19-22. In the current study, unlike the literature, both vertical and horizontal orientations, angles of CMTs and their relationship with their types have been analysed. In the present study, the incidence of CMT was found to be 1.2% in Tekirdağ province and more attention should be paid to CMT vascular evaluation. It is more common for CMT variation to be longest type, type 1, L1 output-level and downward orientation, and these parameters should be considered in vascular surgery or interventional procedures to be performed in the population in this region.

During embryonic period, the 10^th to 13^th vitelline arteries communicate between the aorta and a primitive ventral anastomotic artery. The regression of the ventral anastomosis and vitelline arteries (11^th and 12^th) and the persistence of the 10^th and 13^th roots provide giving origin to the CTR and the SMA. When the 10^th to 12^th vitelline arteries regress and a large portion of the ventral anastomosis persists (13^th), CMT occurs (Figure 5)²³.

There are some classifications about CTR variations available in the literature. Lipshutz²⁴ suggested a classification of CTR into four types in 1917, and Adachi et al.²⁵ classified more detailed anatomical variation of CTR and SMA in six types in 1928. Followed by Morita²⁶, Michels²⁷ and Uflacker²⁸ presented their classifications. In the recent work by Tang et al.¹¹, they have focused on the classification of CMT variation. In the current study, CMT type 1 according to Tang classification is compatible with Adachi type 4, and Tang type 2 is compatible with Adachi type 3.

Although gender and race had an effect on the presence or absence of variations in CTR⁵, most studies^5,29,30 revealed that it had only relationship with ethnicity and origin of the study population, not with gender. According to the literature, Japanese, Caucasian, Korean, Indian and black-coloured populations have more variations of CTR, respectively⁵. On the other hand, in a meta-analysis including 36 studies (total subjects n=17,391) from fourteen countries and four continents, there was a preponderance of males (male/female ratio of 2.36:1). The pooled prevalence estimates of variant CTR with 95% confidence interval depending on the geographical region were mostly found in South America (0.3340) followed by Europe, West Asia, Africa and West Asia, respectively¹². To date, the highest incidence of CMT has been reported as 3.06% in 171 CMT patients¹¹. The incidence of CMT in the current study was detected to be 1.2%.

The length of CTR varies between 8 and 40 mm⁸. In the study by Tang et al.¹¹, they divided 171 CMT patients into long-type (17-39 mm) and short-type (6-14 mm) CMT groups. The long type (61.99%) was more common than the short type. In the current study, CMT length was ranging from 7.6 mm to 38 mm; similarly, the longest type (n=18; mean value=29.4 mm±5.2, range: 19.2 mm-38 mm) was more common than the shortest-type (n=5; mean value=10.78 mm±2.19, range: 7.6 mm-11.8 mm).

In the study by Tang et al.¹¹, the most common type was found to be type 1 that was accounting for 56.14%, followed by type 2 33.33%, type 3 2.34%, and type 4 1.75%. Similarly, in the current study, the most common type was type 1 (65.22%) followed by type 2 (34.78%).

The diameter of CTR has been reported to range from 6.61±1.67 mm to 8±0.9 mm in some studies in the literature^19,20,22. In another study, the mean diameter of CTR was measured as 6.22 mm (ranging from 5.4 mm to 7.3 mm) and the mean diameter of CMT was 8.42 mm (ranging from 5.2 mm to 11.6 mm)¹⁰. In the study on 155 adult cadavers, it was found that the length of CTR increased quickly until the age of 20 years (in new-borns ranging from 3 mm to 8 mm; in adults ranging from 15 mm to 54 mm), while the diameter of CTR increased by the age (new-borns: 1.5-2.0 mm, adults: 3.1-4.3 mm). Also, she mentioned the measured diameter and the length of CTR in pyknics (obese or rounded body structure) were found to be larger (length: 12-29 mm), while in leptosomes (thin body structure), the diameter was smaller (3.1 mm), but the length was greater (39-54 mm)²¹. In the current study, the mean diameter of CMT was measured as 12.06±2.12 mm and a statistically weak negative correlation was found between the CMT length and diameter (p=0.048, r=-0.417), which means that CMT diameter increases as length decreases (Figure 3).

Although the CTR had various levels of origin ranging from the T11 to L1 vertebra, the most common level was found to be T12–L1 (45.83%) followed by T12 (29.17), L1 (22.92) and T11-T12 (2.08%), respectively¹. Selvaraj and Sundaramurthi² reported the similar findings of CTR origin levels that were T12-L1 (70.7%), L1 (18.6%) and T12 vertebra (10.7%), respectively. In the study by 10 CMT patients, the most common level of origin was found to be L1 (30%); T12-L1, L1 end-plate level, L1-L2 (20%) and T12 (10%), respectively¹⁰. The originating level of CTR in pyknics tended to be higher, while in leptosomes, it was lower [21]. In the current study, as shown in the Table 2, the most common level of CMT origin in type 1 was found to be L1-L2 (40%, n=6), followed by T12-L1 level (26.7%, n=4); and in type 2, it was in both L1 and L1-inferior-end-plate levels with the same counts (37.5%, n=3).

The angle between CTR and AA was studied in some literatures^10,31. The angle of emergence of CTR was reported to be less than 90 degrees, ranging from 7 to 83 degrees. Before the first branch, there was an upward shift in 95% (n=306) and downward shift in 4.36% (n=14) of 321 patients. In one patient, CTR remained straight³¹. In another study in CMT patients, in the sagittal plane, the mean angle between the CMT and AA was measured as 26.65 degrees ranging from 13.5 to 38 degrees¹⁰. The angle of CTR in pyknics was greater measuring between 106 and 115 degrees; in contrast, it was smaller (<73 degree) in leptosomes²¹. In the current study, both vertical and horizontal angles were studied and found to be 18.48±14.16 degrees and 73.65±10.74 degrees, respectively. The majority part of the patients was constituted with those with downward orientation (87%, n=20) in vertical angle and had left-sided orientation in horizontal angle (52.2%, n=12) assessment. Both of the reports^10,31 have studied only vertical angle between CMT and AA in which the values are in the similar ranges but none has studied the horizontal angle.

The direction of CTR is influenced by the origin of the hepatic artery and the topography of the pancreatic neck. If CTR is not the origin of the hepatic artery (gastrosplenic trunk), it is directed to the left side, attending as the splenic artery³². Although underdevelopment of rightward component is observed in new-borns, it is the hepatic artery that pulls CTR to the right-side^33,34.

It is very important to know other underlying diseases or pathologies associated with CMT. Aneurysm¹⁵, stenosis¹⁶, thrombosis^13,14, mesenteric ischemia^13,16, arterial compression (egg. median arcuate ligament syndrome)¹⁵ and nutcracker syndrome³⁵ can be associated with CMT which may have important results and may affect the survival specially in the occlusive diseases¹³. Here, CT plays an important role in the detection of variation. Also, as a new technique, cinematic rendering with random sampling computational algorithms and different light maps provides a realistic depiction of anatomical details from CT data³⁶.

Study Limitations

The limitation of the study was that it was conducted with few patients (23 CMTs of 1919 patient population) having CT angiographic examinations. Although the incidence of variation is rare, the patient population participating in this study has the largest patient population included in the studies across the country. However, due to only three female patients, there was not a homogeneous sample group in this study. Due to the retrospective nature of the study, the patients could not be classified in their morphology as leptosomes or pyknics.

CONCLUSION

Having knowledge about arterial variations such as CMT is very important for both surgical approach and planning of interventional procedures and management of CMT-related pathologies. Particularly in vascular interventions, morphometric features of the arterial structures are most of value. As a result, in this study, CMT was found to be mostly type 1, as well as downward (17 degrees±14.28) and left-sided (73 degrees±6.88) orientation.

Ethics

Ethics Committee Approval: Tekirdağ Namık Kemal University Local Ethical Committee of the institution approved the study protocol (approval number: 2020.39.02.13).

Informed Consent: Retrospective study.

Peer-review: Externally peer-reviewed.

Financial Disclosure: The author declared that this study received no financial support.