3DVT, as an emerging cutting-edge technology, is playing an increasingly important role in medical research and clinical practice. In recent years, 3DVT has been widely used in liver and gallbladder surgery [1, 25, 26] and has achieved many results. It makes the complex anatomical relationship between organs and surrounding tissues more intuitive and helps to quantify anatomical data. In the past decade, some 3D software has been developed and used to provide accurate preoperative anatomical information, which has a significant impact on surgical decision-making and planning. Preoperative use of 3D reconstruction technology to visualize key surgical areas enables personalized preoperative planning and precise intraoperative navigation [27]. Some existing studies [19, 28, 29] indicate that 3DVT is a minimally invasive and accurate vascular anatomical evaluation method compared to traditional two-dimensional imaging examinations. Before surgery, the surgeon can use 3DVT to understand the anatomical structure of the surgical area, and observe the branches, shapes, or variations of the arteries from multiple dimensions, angles, and directions to help the surgeon develop a reasonable preoperative strategy. Afterwards, safe and rapid vascular ligation and lymph node dissection can be performed. Splenectomy and pancreatectomy both involve the management of SA, and the difficulty lies in the precise grasp of SA anatomy. Effective control of intraoperative bleeding and reduction of surgical time are important measures to effectively reduce postoperative complications. Therefore, mastering and familiarizing oneself with the anatomy and types of SA is particularly important for external physicians. However, the application of 3DVT in SA anatomy is still relatively limited, and the different historical backgrounds and purposes based on previous technical methods have led to difficulty in unifying the classification results. This study is the first attempt to statistically analyze various anatomical data of SA, combined with various anatomical characteristics such as the arteries themselves and their relationship with the spleen and pancreas. Referring to previous related studies, it has standardized and patterned the 3DVT anatomical classification of SA.
1 The origin, length, diameter, and clinical significance of SA
Accurately identifying the origin of SA and its measurement features such as length and diameter is not only crucial for surgical planning, but also for avoiding iatrogenic injuries during the surgical process. Therefore, familiarizing oneself with anatomical parameters such as its origin and diameter is of great clinical significance. A anatomical study based on 62 cadaveric abdominal arteries [30] suggests that surgeons must have a clear understanding of the exact location of the arterial origin, and even predict potential locations for variation, as well as arterial length, measurement relationships, and arterial orientation. These pieces of information can help every surgeon avoid arterial damage during surgery.
The origin of SA occurs during embryonic development, with the intestinal artery connected by anterior longitudinal anastomosis. Among the four arterial roots, two disappear, and the remaining anastomosis produces SA, common hepatic artery, and left hepatic artery. Clement et al. [31] observed in a study of cadavers and imaging that 90.5% of individuals exhibited a typical three branch pattern in the abdominal artery, where SA originated from the abdominal trunk. A large sample study based on 5002 patients by Song et al. [32] found that approximately 89.1% of SA originated from the abdominal trunk using DSA and CT techniques. In this study, 99% (99/100) of individuals had SA originating from the abdominal trunk, which is typically manifested in the form of the common hepatic artery, left gastric artery, and SA. The statistical quantity is higher than the above two studies, but the overall trend is consistent. This may be due to the small sample size and racial differences among the included study subjects. In this study, only 1% (1/100) of SA originated from the abdominal aorta, and no other arteries were found to originate. This data is similar to the results of a study in India [33], which also found that SA can originate from the common hepatic artery or superior mesenteric artery. This phenomenon suggests that although SA originating from outside the abdominal trunk is rare, it still needs to be taken seriously to avoid accidental injury to other blood vessels during surgery due to empirical procedures.
The average diameter of the starting part of SA measured in this study is 5.59 ± 1.06mm, with a minimum value of 3.27mm and a maximum value of 5.47mm. The average diameter of the terminal part is 4.63 ± 0.98mm, with a minimum value of 2.58mm and a maximum value of 7.58mm. There are differences in research data among different researchers. Ma Yanwen et al. [34] used a vernier caliper to directly measure the SA terminal diameter of adult corpses, with an average of 5.40 ± 1.50m, a minimum value of 2.1mm, and a maximum value of 8mm. The maximum diameter in both research data is much smaller than the clamping range of the large titanium clip (12.5mm). Although the average terminal diameter in this study is relatively small, the difference is not significant. The average length of SA measured by 3DVT in this study was 116.60 ± 30.71mm, with the shortest being 49.77mm and the longest being 272.99mm. The reports on SA length measurement are similar to diameter research methods, which often use cast specimens for direct measurement. However, due to the hardening and contraction of cadaver specimens after long-term formalin fixation, it can lead to result errors and be limited to outdated research methods and technical means. And this study is based on the good blood vessels of healthy adults under normal function, with advanced technical methods, relatively reliable data, and more accurate results. This once again proves the advantages and value of 3DVT in studying anatomy. Another clinical significance of this study is that using 3DVT to accurately determine SA length and diameter data can aid in interventional surgery for spleen and splenic vascular related diseases. Ogawa et al. [35] believe that vessel diameter is one of the risk factors for thrombosis in the portal vein after partial SA embolization intervention. Having a clear understanding of the length and diameter of the main trunk and its branches of SA before surgery can guide the surgeon in personalized selection of catheters. By designing the diameter of the catheters, the embolization range can be strictly controlled during surgery to avoid accidental emboli, and the thickness of the catheters can be controlled to avoid vascular rupture or damage to other organs. This study demonstrates that accurate and reliable anatomical research data on the origin, diameter, and length of SA can provide value and improve surgical safety for interventional procedures such as placement or removal of arterial stents.
2Morphological classification and clinical significance of SA
A study from Japan [36] used 3DVT to classify SA into two types. Type A was defined as SA bending and extending above the pancreas, with a total sample size of 4 cases; Type B is defined as SA entering the dorsal side of the pancreas relatively directly, with a total sample size of 2 cases. Afterwards, Wada et al. [37] classified SA into two main anatomical types based on their 3DVT classification, including the S-type, where SA bends and passes through the pancreas, accounting for 83% of the total study; Type D refers to SA that runs straight and backs against the pancreas, accounting for 17%. The essential classification criteria for the above two are based on the curved shape of SA, but the sample size is relatively small, with only 30 patients included in the latter; And it did not provide a detailed description of the approximate shape and specific number of bending indicators. In reality, the morphology of SA is quite complex, and the classification by Japanese scholars does not cover all types, which cannot fully and intuitively display the entire morphology of the SA backbone. This study found that the morphology of SA during the journey not only covers the types described in the above studies, but also has many complex and curved types, indicating that the morphology of SA has individual heterogeneity and is difficult to predict. Therefore, SA is further classified into four types based on its morphological type: l-type, p-type, s-type, and irregular type. The total sample size is higher than the above two studies, and on this basis, two additional descriptions of p-type and irregular type have been added, covering basically all forms of SA. Among them, S-type is the most common, accounting for 45% (45/100), while L-type is the least common, accounting for 1% (1/100). Different morphological types determine different surgical methods and difficulties. When performing LDP surgery, studies by some scholars [36,37] have shown that adopting selective different surgical approaches for different types of SA is beneficial for exposing SA. Compared with the control group without selective approach surgery, the experimental group significantly shortened the median surgical time and median blood loss. Nagakawa et al. [38] believe that treating SA with higher curvature is more difficult, and straightening SA as much as possible can reduce the surgical difficulty of LDP, that is, dealing with L-type SA is the simplest. Familiarity with the SA morphological typing of 3DVT can help improve the success rate and safety of LDP. Adopting this personalized approach for each patient can select a targeted surgical approach in the shortest possible time, quickly expose and bandage the arteries, and minimize contact with pancreatic parenchyma and blood vessels. This strategy can shorten the surgical time of LDP and reduce the amount of bleeding. For example, during LDP surgery, targeted suprapancreatic approach can be implemented for the most common S-type SA, thereby reducing postoperative complications and patient pain.
3 The spatial classification and clinical significance of SA Pandey et al. [15] analyzed the anatomy of 320 corpses and classified the relationship between SA and the pancreas into four types: the most common type was the suprapancreatic type (74.1%), followed by the enteropancreatic type (18.5%), intrapancreatic type (4.6%), and postpancreatic type (2.8%). This study only counted the relationship between a certain segment or part of SA and the pancreas. After observing 100 3DVT images, it was found that the position relationship between SA and the pancreas is complex and variable, but with certain regularity. In order to comprehensively present the complete spatial relationship between SA and the pancreas and provide guidance for clinical pancreatic and splenic surgery, this study described the entire course of the SA trunk and can be mainly divided into the following categories based on the position relationship between SA and the pancreas: Type I: SA travels along the upper edge of the pancreas to the splenic hilum, with 23 cases (23/100); Type II: In 57 cases (57/100), the middle 2 1/4 segments of SA passed through the pancreas or traveled along the posterior part of the pancreas to the splenic hilum; Type III: Two distal 1/4 segments of SA passed through the pancreas or traveled along the pancreas to the splenic hilum, with 4 cases (4/100); Type IV: In 16 cases (16/100), all 3 l/4 segments of the distal end of SA passed through the pancreas or traveled along the pancreas to the splenic hilum. This classification is based on the classification of Xu Weili et al. [39]. This study classified SA using color Doppler ultrasound imaging, with Type I accounting for the highest proportion of 47% and Type III accounting for the lowest proportion of 6%. The spatial characteristics of SA presented in 3DVT images are basically consistent with them. In my study, the number of Type III is similar, but the number of Type I is significantly different. The reason may be that ultrasound methods rely too heavily on the examiner's technique, with strong subjectivity. The level of different examiners has a significant impact on the results. At the same time, ultrasound is prone to interference from abdominal gas and liquid during propagation, ultimately leading to differences in typing results compared to this study. 3DVT collects objective data and uses computer systems to generate standardized images. Researchers then use 3DVT to rotate, zoom in, and observe the specific positional relationship between SA and the pancreas in the images. Afterwards, they complete classification statistics under direct vision, resulting in higher reliability of the classification results. For type III and IV SA, due to their close relationship with the pancreas, surgeons are prone to tearing open SA and damaging the pancreas during LDP, which increases the difficulty of surgery. Nakata et al. [40] divided 50 patients who planned to undergo LDP into 30 cases of buried type and 20 cases of non buried type after preoperative 3DVT to determine whether SA entered the pancreas during walking. Subsequently, surgery was performed separately, and the results showed that the median surgical time for buried type SA patients was significantly longer than that for non buried type SA patients (285.0 and 235.5 minutes, respectively; P<0.01). The median time required to separate buried type SA (25.8 minutes; range 4.0-101 minutes) was significantly longer than that for non buried type SA (7.0 minutes; range 1.0-27.0 minutes). Therefore, preoperative use of 3DVT to understand the type of SA in advance can predict the difficulty of managing SA during LDP surgery and the expected surgical duration. When implementing LS, for common types I and II, the main trunk of SA can be ligated as early as possible to prevent intraoperative bleeding and shrink the spleen. For rare types III or IV, as SA is located behind or inside the pancreas, it is difficult to separate from the pancreas, and hasty separation may cause bleeding. Therefore, careful treatment from the tail of the pancreas should be performed to expose the splenic pedicle [41].
4 The differentiation of splenic hilum in SA and its clinical significance
Current research indicates that the vascular anatomy around the splenic hilum is very complex. The SA terminal branching structure is complex and unpredictable due to embryological adhesions. Daisy et al. [18] found that at 2-4cm proximal to the splenic hilum, SA was divided into two branches with a total of 80% (160/200) or three branches with a total of 20% (40/200) entering the dominant splenic lobe and supplying the corresponding splenic lobe. According to domestic reports by Jiang Hongchi et al. [42], the two branch type accounts for 96.15%; Three branch type accounts for 3.85%, and no single or multiple branch types were found. Wang Lianchen et al. [43] reported that the splenic lobar artery can be divided into one branch type, two branch type, and three branch type, accounting for 3.0% -5.7%, 76.9% -98.0%, 2.0% -23.8%, respectively. In addition, there are multiple branch types, which are relatively rare. In this study, there were 4 cases of the same type, accounting for 4% (4/100); There are 76 cases of two branch type, accounting for 76% (76/100); There are a total of 15 cases of the three branch type, accounting for 15% (15/100); There are 5 cases of multi branch type, accounting for 5% (5/100). Similar to the results of domestic and foreign literature, the two branch type is dominant, while the one branch type and the multi branch type are rare but exist. The number of branches of SA in the splenic hilum determines the lobulation of the spleen. If it is a two branch type, the spleen is divided into upper and lower lobes; If it is a three branch type, the spleen is divided into upper, middle, and lower lobes. Some middle lobe arteries only supply the middle lobe, while others branch out to supply the upper and lower lobes. Due to the dominant position of the two branch type, most spleens are divided into the upper lobe and middle lobe. Due to the elucidation of splenic function and its core role in immune homeostasis, partial splenectomy has become a better option for preserving postoperative splenic function. Partial splenectomy is feasible for patients with minor splenic trauma, benign lesions, and splenic hyperfunction [44]. After performing preoperative SA classification, the patient's SA in the splenic hilum area is classified into the above types to select the most suitable surgical procedure for the individual. The SA branch to be excised from the splenic lobe can be ligated based on the 3DVT classification of the splenic hilum area, which can effectively reduce pancreatic injury and postoperative fistula formation. At the same time, the author believes that for rare multi branch SA, special attention should be paid to the distribution of its branches during surgical treatment of blood vessels to avoid unnecessary damage and bleeding.
This study innovatively proposed the classification of the relationship between the SA branch and the distal end of the pancreas using 3DVT: right-sided pancreatic tail type and left-sided pancreatic tail type. Among them, right-sided pancreatic tail type is more common, accounting for 55% (55/100). By using 3DVT compared to cast specimens, anatomical data of the human body under normal physiological conditions can be obtained. The distance between the SA branch and the end of the pancreatic tail was measured to be 15.99 (0-127.23) mm, which provides anatomical basis for the priority approach to the pancreatic tail for LDP surgery. For benign pancreatic tumors or those with low malignant potential located at the tail of the pancreatic body, it is feasible to preserve the LDP of the spleen. This surgery is widely accepted worldwide due to its advantages such as fewer complications compared to distal pancreatectomy combined with splenectomy [45]. Normally, the preservation of the spleen in LDP surgery involves an anterograde approach through the neck of the pancreas, which starts along the occupied area, frees the splenic vessels, and then separates them distally until the lesion and splenic vessels are completely separated [46]. However, when there is adhesion between the occupying space and the splenic blood vessels, separation often fails, and the probability of splenic blood vessel damage is high, which can lead to the occurrence of massive bleeding. A study [47] suggests that the pancreatic tail priority approach can be used in combination with the anterograde approach to simultaneously expose the proximal and distal splenic vessels of the lesion, and finally concentrate on treating the splenic vessels with close local adhesions, which can reduce the difficulty of surgical operations. The surgeon uses the pancreatic tail as an anatomical marker to search for the SA branch during surgery, and uses 3DVT typing results to locate the SA branch on the left or right side of the pancreatic tail by approximately 15.99 (0-127.23) mm, followed by vascular dissection, which can achieve twice the result with half the effort. At the same time, preoperative 3DVT examination can not only display the location, size, and invasion of adjacent organs and blood vessels of pancreatic tumors, but also quickly identify branching points through SA's three-dimensional classification, reducing surgical time. Ligating SA near the bifurcation point can avoid damaging the arterial arch between the gastric short vessel and the left gastric omental artery, ensuring its integrity [48].
The distance between the SA branch and the splenic hilum measured in this study was 19.21 (0-68.15) mm. When a patient plans to undergo splenectomy due to acute trauma causing splenic rupture, the SA trunk can be ligated approximately this distance to timely control bleeding. However, the ligation should not be placed too close to prevent the blood vessels in the tail of the pancreas from being cut off. The advantage of splenic portal area 3DVT classification lies in quantifying the preoperative anatomical data of the SA terminal branch in the splenic portal area through 3DVT, establishing the splenic portal area SA classification of 3DVT, which can provide important basis for clinicians to accurately formulate surgical plans before surgery.
5 The distance classification of SA and its clinical significance
Ma Junxun et al. [49] classified the distance between SA and the splenic hilum from 0.6-2cm into the terminal branch called the concentrated type, accounting for 30%; Another type of SA, with a distance of more than 2cm from the splenic hilum, separates into dispersed terminal branches, accounting for 70%. A study on the imaging data of CTA examinations of 115 patients with SA included by some scholars in China [50] showed that there were 38 cases of concentrated SA, accounting for 33% (38/115); There are 77 cases of dispersed SA, accounting for 67% (77/115). Zheng et al. [17] investigated the effect of SA anatomy on laparoscopic splenic lymph node dissection. They also classified SA into concentrated and dispersed types based on the distance between the arterial branches and the splenic hilum area, and found that the average surgical time and average blood loss of the concentrated type were lower than those of the dispersed type. Huang et al. [51] believe that centralized SA is beneficial for shortening the dissection time of lymph nodes in the superior and inferior regions of the splenic hilum. It can also help novice surgeons gain experience in successful cases, build confidence, and shorten the learning curve of the surgery. These studies did not mention the comb shape. After consulting relevant literature, this study classified according to the above criteria, with 42 cases of concentrated type accounting for 42% (42/100) and 47 cases of dispersed type accounting for 47% (47/100). The results are similar to domestic and foreign reports, showing that dispersed SA is dominant in normal adults. Moreover, based on the research of the first two, the author believes that it is easier to clear the concentrated SA surrounding lymph nodes during splenic hilum lymph node dissection. Similarly, in LS, the distance classification of SA determines the surgical approach and success or failure. Due to the long distance from the origin of the splenic lobar artery in dispersed SA to the splenic hilum, sufficient length of the splenic lobar artery can be separated at the splenic hilum, and then branches can be cut off one by one, without the need to cut off the main trunk of SA to remove the spleen and reduce intraoperative bleeding. However, the starting point of the concentrated splenic lobe artery is short from the splenic hilum, making it difficult to separate and ligate the splenic lobe artery one by one. Therefore, the main trunk of SA should be directly disconnected. Conventional preoperative imaging examinations make it difficult to distinguish the distance classification of SA due to the difficulty in directly measuring the distance between the scoring branch and the splenic hilum. The use of 3DVT can directly measure the distance accurately through the system's built-in measurement tool. After pre classifying the SA type, targeted surgical plans can be formulated to avoid temporary differentiation of arterial types during surgery, which may lead to temporary decisions or changes in surgical methods that harm the interests of patients. This study also has some limitations. Firstly, only 3DVT was used for retrospective analysis and classification of SA 3D images obtained from enhanced CT examination in one hospital. Due to the possibility of small blood vessels being overlooked in three-dimensional images, it is necessary to compare them with actual intraoperative observations; Secondly, the sample size is not large enough, and there is no statistical analysis of the impact of individuals of different ages and races on SA anatomical typing, which cannot fully represent all situations in the actual population; The cost of accepting 3DVT is relatively high, and the cost of seeking medical treatment for patients is slightly higher. In summary, this study utilized 3DVT to conduct anatomical research and standardized classification of SA, which can provide safe implementation of various surgeries.