we used 28 male and 5 female new zealand white rabbits ( weight , 2.53.0 kg ) , purchased from tokyo laboratory 
 animal science co ( tokyo , japan ) .
the present study was approved by the research ethical committee for animal 
 experimentation of the tokyo university of agriculture and technology .
the rabbits were sacrificed with intraperitoneal injection of sodium pentobarbital ( 60 mg / kg ) and then perfused 
 with fixative containing either 4% paraformaldehyde and 0.05% glutaraldehyde or 10% formalin . in the fixed 
 cadaver in the dorsal position ,
some of their left ribs were removed to facilitate thoracic aortic incision , 
 through which a cannula was inserted caudally to be injected with 3 to 8 ml of the colored 
 latex ( neoprene latex 601a or 842a , showa denko , kawasaki , japan ) .
after further fixation for more than 7 days 
 in 10% formalin , we characterized the macroscopic arterial distribution to the spleen .
the rabbit spleen was located on the left caudolateral aspect of the stomach ( fig .
1.a : photograph showing the rabbit spleen located on the left caudolateral aspect of the stomach . the left 
 caudoventrolateral view .
b : photograph showing that the splenic artery arises as the first independent 
 branch of the celiac artery . the left caudoventrolateral view .
abbreviations used in this and the following figure : a , artery ; br , branch ; du , duodenum ; sp , spleen ; and 
 st , stomach . ) .
the splenic artery arose as the first independent branch of the celiac artery in all the rabbits 
 examined ( fig .
1b ) that runs along the visceral surface of the spleen . upon 
 reaching the hilus ,
the splenic artery ran ventrally along the hilus to give off different numbers of the 
 splenic branches to the spleen ( fig .
b : schematic drawing of a. c : photograph of a case with 7 splenic branches 
 and no common trunk .
d : schematic drawing of c. ) and then continued as the left gastroepiploic artery toward the greater curvature of the stomach ( figs .
each splenic 
 branch arose as either an independent branch of the splenic artery or as a trunk in common with a short gastric 
 artery ( this trunk will be simply referred to as  common trunk  hereafter ) .
the first branch of the splenic 
 artery was always a short gastric artery or the common trunk of a splenic branch with a short gastric artery 
 ( fig .
2 ) , but never a splenic branch . in cases in which the first 
 splenic branch arose from the common trunk , the branch usually entered the hilus near the splenic dorsal 
 extremity .
in contrast , in cases where the first splenic branch arose independently from the splenic artery , the 
 branch entered the hilus somewhat distant from the dorsal extremity ( fig . 
 2 ) .
a : photograph showing the rabbit spleen located on the left caudolateral aspect of the stomach . the left 
 caudoventrolateral view .
b : photograph showing that the splenic artery arises as the first independent 
 branch of the celiac artery .
abbreviations used in this and the following figure : a , artery ; br , branch ; du , duodenum ; sp , spleen ; and 
 st , stomach . a : photograph of a case with 6 splenic branches .
b : schematic drawing of a. c : photograph of a case with 7 splenic branches 
 and no common trunk .
d : schematic drawing of c. the number of the splenic branches varied from 3 to 10 according to the specimen ( fig . 3afig .
3.a : pie chart showing the incidence of the number of the splenic branches of the splenic artery .
b : pie 
 chart showing the incidence of the common trunk(s ) of the splenic branches with short gastric 
 arteries . ) : 3 branches were present in 2 rabbits ( 6% ) , 4 branches in 3 rabbits ( 9% ) , 5 branches in 7 rabbits ( 21% ) , 
 6 branches in 8 rabbits ( 25% ) ( fig . 2a and 2b ) , 7 branches in 6 
 rabbits ( 18% ) ( fig . 2c and 2d ) , 8 branches in 4 rabbits ( 12% ) , 9 
 branches in 2 rabbits ( 6% ) and 10 branches in 1 rabbit ( 3% ) . furthermore ,
the number of the common trunk ( s ) of 
 the splenic branches with short gastric arteries ( fig . 2a and 2b ) 
 varied from 0 to 4 ( fig .
3b ) : 0 common trunk in 5 rabbits ( 15% ) ( fig . 2c and 2d ) , 1 common trunk in 12 rabbits ( 37% ) , 2 common trunks in 7 
 rabbits ( 21% ) , 3 common trunks in 6 rabbits ( 18% ) and 4 common trunks in 3 rabbits ( 9% ) ( fig . 2a and 2b ) .
no correlation was observed between the number of the splenic 
 branches / common trunk(s ) and the splenic arterial branching pattern . a : pie chart showing the incidence of the number of the splenic branches of the splenic artery .
b : pie 
 chart showing the incidence of the common trunk(s ) of the splenic branches with short gastric 
 arteries .
the dorsoventral length of the spleen varied from 31 to 68 mm , and 50% of the spleens were between 50 and 60 mm 
 long ( fig .
b : scatter diagram showing 
 the correlation between the dorsoventral length of the spleen and the number of splenic branches 
 ( r=0.6 , p=0.008 ) . ) .
4b ) ( r=0.60 , p=0.008 ) , but did not correlate with 
 the number of the common trunk(s ) of the splenic branches with short gastric arteries ( r=0.19 ) . 
 there was no correlation between the number of splenic branches and the number of the common trunk(s ) 
 ( r=0.12 ) .
b : scatter diagram showing 
 the correlation between the dorsoventral length of the spleen and the number of splenic branches 
 ( r=0.6 , p=0.008 ) . there were no gender differences in the number of the splenic branches or common trunk(s ) , the pattern of the 
 splenic arterial branching , or the dorsoventral length of the spleen .
the present study characterizes in great detail the individual anatomical variations of the arterial supply to 
 the spleen in the rabbit . in all rabbits
. however , bednov and malinovsk   demonstrated that not 
 the splenic artery but the hepatic artery was the first branch in 1 out of 30 cases that they examined .
this one 
 rabbit is considered to be an exceptionally rare case , because other previous reports in the rabbit [ 1 , 2 , 14 ] consistently showed that the splenic artery was the first branch of the celiac artery , in 
 agreement with our present results . in rodents , there are individual and/or species variations ; the splenic 
 artery is usually the first independent branch of the celiac artery in the mediterranean pine vole , muskrat , wood mouse   and degu , frequently not the 
 first independent branch in the dormouse , and never in the north 
 american beaver   and guinea pig [ 4 , 16 ] .
we found the common trunk(s ) of the splenic branches with short gastric arteries in 85% of the rabbits examined 
 in this study ( fig .
the number of the common trunk(s ) varied from 
 0 to 4 , with 1 common trunk ( 37% ) being the most frequent .
did not describe such common trunks , whereas bednov and malinovsk 
  mentioned the existence of at least 1  stem  in some of their cases , 
 though their description was vague .
these differences may be due to the possibility that abidu - figueiredo 
 et al . used another breed of new zealand rabbits , such as new zealand red , and bednov and malinovsk 
 used breeds other than the new zealand white . in two studies in rodents ( dormouse   and degu ) , which are the closest relative to 
 the lagomorph , it was reported that a trunk of the splenic artery gave off branches to the dorsal portion of the 
 spleen and to part of the left visceral surface of the stomach .
branches that provide 
 the splenic branches and short gastric arteries are also described in the dog .
these trunks in rodents and dogs correspond to the common trunk observed in the rabbit in the 
 present study . in the chinchilla , one trunk , which is called the gastrosplenic 
 artery ,
supplies the dorsal spleen and the greater curvature of the stomach and the other , which is called the 
 splenic artery , supplies the central and the ventral spleen .
however , these trunks branch off from the celiac 
 artery at the same level .
it is considered that these two trunks in the chinchilla may correspond to one common 
 trunk of the splenic artery with a short gastric artery in the rabbit .
the number of the splenic branches varied from 3 to 10 with 6 branches ( 25% ) being the most frequent number 
 among the rabbits examined in this study . however , abidu - figueiredo et al .   studied 30 new zealand rabbits ( weight , 2.5 kg ) and obtained different 
 results in that the number of the splenic branches varies from 1 to 5 with 3 branches ( 33.3% ) being the most 
 frequent . in the rat ,
whose spleen is shaped similar to that of the rabbit , it is reported that the number of splenic branches was 5 to 8 .
this finding is similar to that from our study , wherein 76% of the rabbits have 5 to 8 splenic 
 branches .
we found a moderate correlation between the dorsoventral length of the spleen and the number of splenic 
 branches ( r=0.6 , p=0.008 ) .
however , there was no correlation between the 
 length and the number of the common trunk(s ) or between the number of splenic branches and the number of common 
 trunk(s )
. furthermore , the number of these branches and common trunk(s ) does not relate to their branching 
 pattern .
therefore , arterial variations demonstrated by the present study should always be taken into account 
 when performing experimental or veterinary surgery in rabbits .
 the rabbit , which is widely used as an experimental animal and is also popular as a companion animal , has a 
 flat and elongated spleen with the longitudinal hilus running along its visceral surface . 
 the spleen receives 
 via the hilus an arterial supply that is essential for splenic nutrition and normal functioning . 
 however , the 
 distribution and variation of the arteries to the spleen have not been studied in detail . 
 this study 
 investigated anatomical variations of splenic arterial supply in 33 new zealand white rabbits with a colored 
 latex injection into arteries . 
 we also examined whether the length of the spleen correlated with the number of 
 the splenic branches of the splenic artery . 
 the splenic artery always arose as the first independent branch of 
 the celiac artery and ran along the splenic hilus to usually provide 6 ( range , 3 to 10 ) splenic branches to 
 the spleen . 
 there was a moderate correlation ( r=0.6 ) between the number of splenic branches 
 and the longitudinal length of the spleen . 
 the splenic branches often arose as a trunk or trunks in common 
 with short gastric arteries . 
 the number of common trunk(s ) was usually 1 ( range , 0 to 4 ) . 
 the data showed that 
 the pattern and number of arterial branches to the spleen varied according to the individual animal , 
 suggesting that such variations should be considered when performing experimental and veterinary surgical 
 treatments in rabbits . 
MATERIALS AND METHODS
RESULTS
DISCUSSION