Introduction
The spleen is a highly vascular and friable organ. It is the largest secondary lymphoid organ, which contains 25% of the body lymphoid tissue and has both haematological and immunological functions. Spleen is supplied by splenic artery which is the largest branch of coeliac trunk.1 It traverses through the lienorenal ligament to reach near the hilum of the spleen, where it divides into two or three primary branches, each of which is subdivided mostly into two or four secondary branches. Moreover, a superior polar arteries and inferior polar arteries are given from splenic trunk or from one of its primary branches, which goes to the poles of the spleen, without entering the hilum. It is called as superior and inferior polar branches. The human spleen is divided accordingly into two or three main segments. Each main segment is also divided usually into two to four less constant secondary segments. The segments of spleen are separated by a definite avascular plane.
The partial removal of the spleen is possible, as the spleen is divided into segments, separated by fibrous septa and each segment is supplied by its own main artery.2 The presence of splenic segmentation could be attributed to its development or to the terminal division of the artery.
Better anatomical knowledge about segmental distribution of splenic artery and its variations are important for the partial removal of the organ. So, keeping the applied aspect and clinical significance of segmental branches of splenic artery and to add more knowledge to the existing one, the present study was undertaken to study the segmental branches of splenic artery which divide the spleen into various segments, its pattern of distribution and also to find out any inter-segmental arterial anastomosis by dissection method.
Aims and Objectives
To study the branching pattern of the segmental branches of splenic artery and to find out if there is any the anastomosis between the segmental branches.
Materials and Methods
The present study is conducted on 79 Human cadaver spleens, irrespective of their age and sex, fixed in 10% formalin solution, collected from the department of Anatomy and Forensic Medicine, Mysore Medical College and Research Institute.
The gross dissection was done by following the guide lines of Cunningham’s Manual. The spleen was identified and freed from the posterior abdominal wall and stomach by cutting through the gastrosplenic and lienorenal ligaments. The splenic artery was cut about 10 cm proximal to hilum of spleen, then the spleen was removed. The fascia and fat was cleared at the hilum to expose the segmental branches of the splenic artery. Firstly, the primary segmental branches of the splenic artery and its branching patterns were identified and noted, then by removing the parenchyma along the primary branches by piecemeal dissection the secondary branches and also inter segmental arterial anastomosis if any were noted.
Results
Two primary segmental branches were seen in 56 (70.9%) specimens, three primary segmental branches were seen in 19 (24.1%) specimens and four primary segmental branches were seen in 4 (5.1%) specimens.
Superior polar artery was present in 18 (22.8%) specimens and inferior polar artery was present in 32 (40.5%) specimens and both superior and inferior polar artery was seen in 5 (6.3%) specimens.
Superior polar artery arising from main trunk was present in 12 (67%) specimens and superior polar artery arising from primary branch seen in 6 (33%) specimens.
Inferior polar artery was seen arising from main trunk in 15 (47%) specimens, from left gastroepiploic artery in 9 (28%) specimens and from primary branch in 8 (25%) specimens.
Anastomosis between the primary segmental branches were seen in 11 (13.9%) specimens.
The extra-parenchymal anastomosis of primary segmental branches was seen in 5 (6.3%) specimens. The intra-parenchymal anastomosis was seen in 3 (3.7%) and sub-capsular type of anastomosis was seen in 3 (3.7%) specimens.
The distributive type of branching pattern was present in 50 (63.3%) specimens. The marginal type of branching pattern was present in 29 (36.7%) specimens.
Figure 1
Extra-parenchymal anastomosis between superior and inferior primary branches
EP. Anas. – Extra Parenchymal Anastomosis)
Figure 3
Sub-capsular type of anastomosis between superior and inferior primary branches
SC. Anas. – Sub capsular Anastomosis)
Table 1
Number of primary segmental branches of splenic artery
|
S. No. |
Primary segmental branches |
Number of specimens |
Percentage (%) |
|
1 |
One |
Nil |
0 |
|
2 |
Two |
56 |
70.9 |
|
3 |
Three |
19 |
24.1 |
|
4 |
Four |
4 |
5.1 |
|
5 |
Total |
79 |
100 |
Table 2
Types of anastomosis
|
Types of anastomosis |
Number of specimen |
Percentage (%) |
|
None |
68 |
86.3 |
|
Extra-parenchymal |
5 |
6.3 |
|
Intra-parenchymal |
3 |
3.7 |
|
Sub-capsular |
3 |
3.7 |
|
Total |
79 |
100.0 |
Table 3
Comparison of number of primary segmental branches of splenic artery with the previous studies
|
Author |
Number of specimens studied |
Number of primary segmental branches |
||
|
2 |
3 |
4 |
||
|
Gupta CD et al. (1976)3 |
50 |
84% |
16% |
- |
|
Mikhail Y et al. (1979)4 |
25 |
77% |
23% |
- |
|
Katrisis E et al. (1982)5 |
70 |
88.7% |
14.3% |
- |
|
Mandarin LCA (1983)6 [6] |
25 |
68.2% |
10.6% |
4.5% |
|
Garcia PJA (1988)7 |
181 |
92.82% |
7.18% |
- |
|
Sow ML (1991)8 |
32 |
84% |
16% |
- |
|
Silva LFA (2010)9 |
- |
93.34% |
6.66% |
- |
|
Chaware PN et al. (2012)10 |
- |
85.58% |
14.42% |
- |
|
Swamy VL et al. (2013)11 |
60 |
66% |
17% |
17% |
|
Londhe SR et al. (2013)12 |
50 |
90% |
10% |
- |
|
Present study |
79 |
70.9% |
24.1% |
5.1% |
Table 4
Comparison of polar arteries with the previous studies
|
Author |
Polar artery |
||
|
Superior |
Inferior |
Both |
|
|
Present Study |
22.8% |
40.5% |
6.3% |
|
Mikhail Y et al4 |
18% |
50% |
12% |
|
Garcia PA et al7 |
29.28% |
44.75% |
10.49% |
|
Chaware PN et al10 |
28.82% |
42.34% |
11.7% |
|
Swamy VL et al11 |
41.6% |
25% |
16.6% |
|
Londhe SR et al12 |
32% |
56% |
24% |
Table 5
The comparison of anastomosis between segmental branches with the previous studies
|
Author |
Observation |
|
Present study |
13.9% |
|
Gupta CD et al3 |
No anastomosis |
|
Garcia PJA et al7 |
19.89% |
|
Mandarim LCA et al6 |
16.7% |
|
Chaware PN et al10 |
1.80% |
Discussion
Spleen is supplied by splenic artery, which terminates at the hilum by dividing into 2 or 3 terminal branches. These are named as superior, middle and inferior primary branches. These branches supply a particular part of the spleen which is separated by an avascular plane. Thus, these branches divide the spleen into definite arterial segments. So these arteries can be considered as the primary segmental branches.5 In the present study two primary branches were seen in 56 (70.9%) specimens, three in 19 (24.1%) specimens and four in 4 (5.1%) specimens. Other studies showed only 2 to 3 primary branches. In this study we have observed 2 to 4 primary branches. The comparison of number of primary branches with the previous studies is given in Table 3.
In some spleens, a branch arising from splenic artery itself or one of its primary branch which does not pierce the hilum, but goes to the poles of spleen. These are known as superior and inferior polar arteries. These arteries also supply a particular segment of spleen, which can be considered as the polar segments.16 In our study we observed superior polar artery was present in 18(22.8%) specimens and inferior polar artery was present in 32 (40.5%) specimens and both superior and inferior polar artery was seen in 5 (6.3%) specimens. The comparison between other studies is given in Table 4.
Superior polar arteries arising from main trunk was present in 12 (67%) specimens and superior polar arteries arising from primary branch were seen in 6 (33%) specimens. Inferior polar artery was seen arising from main trunk in 15 (47%) specimens, from left gastroepiploic artery in 9 (28%) specimens and from primary branch in 8 (25%) specimens.
Katrisis E et al5 in their study noted that, the polar arteries arise either from main trunk or primary branch. Silva LFA et al9 observed 16% arising from main trunk and 20% arising from terminal branches. Swamy VL et al11 noted all polar arteries arising from main trunk only.
The spleen is divided into segments; each segment is supplied by its own segmental branches. These segments are separated by a definite avascular plane. But rarely there may be an inter-segmental anastomosis. In the present study, anastomosis between the primary segmental branches seen in 11 (13.9%) specimens. The comparison of anastomosis between segmental branches with previous studies is given in Table 5.
The inter-segmental anastomosis can be of three types.
In the present study we observed, the extra-parenchymal anastomosis of primary segmental branches were seen in 5 (6.3%) specimens, the intra parenchymal anastomosis was seen in 3 (3.7%) specimens and sub capsular type of anastomosis was seen in 3 (3.7%) specimens. Comparison of type of anastomosis with the previous studies is given in Table 6.
Based on terminal branching pattern, the splenic artery pedicle can be classified into two types.
Distributive type where the splenic artery divides away from the hilum of the spleen with long terminal branches that enters through the hilum.
Marginal type where the artery divides at the hilum with short terminal branches.
In the present study we observed, the distributive type of branching pattern was present in 50(63.3%) specimens and the marginal type of branching pattern was present in 29(36.7%) specimens.
A study conducted by Henschen et al.17 classified three types of pattern and observed, short distribution in 10%, long distribution in 40% and marginal type in 46%. The comparison of present study with previous studies is given in Table 7.
Conclusion
The spleen is a highly vascular and friable organ. It is the largest of secondary lymphoid organ, which contains 25% of the body’s lymphoid tissue and has both haematological and immunological functions. Total splenectomy is commonly done after a splenic injury, which leads to decrease in the immunity and predisposes the normal host to overwhelming life threatening infections and also creates an altered haematological picture. To overcome this, partial splenectomy can be done by ligating a particular segmental branch of splenic artery.
The partial removal of the spleen is possible, as the spleen is divided into segments, separated by fibrous septa and each segment is supplied by its own main artery. The presence of splenic segmentation could be attributed to its development or to the terminal division of the artery. Better anatomical knowledge about segmental distribution of splenic artery and its variations are important for the partial removal of the organ.
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