A n A t t e m p t to C r e a t e S p l e n o - s y s t e m i c A n a s t o m o s i s in t h e R a t Motonori SAKU,*J6rgen NORDENSTROM,**and Bengt BORJESSON*** A B S T R A C T : A selective diversion of the splenic venous flow into the systemic circulation was attempted in the rat. A combination of the subcutaneous splenic transposition and the ligation of the splenic vein as a two stage operation was carried out in 15 rats. A rich collateral system developed rapidly from the transposed spleen to the systemic circulation. Angiography, performed four weeks after the ligation, revealed that almost all of the injected contrast medium was diverted into the systemic circulation via those newly developed collaterals. The described method as an experimental model could be of value in the search for a spleno-hepatic axis. KEY W O R D S : spleno-systemic anastomosis, subcutaneous splenic transposition, hepato-splenic axis.
INTRODUCTION S i n c e Banti 1 first reported an influence of the spleen on the liver in 1894, many investigators have discussed this subject. However, the evaluation of the role of the spleen is hampered by the lack of an appropriate experimental model. There is still no physiological explanation to the fact that the splenic venous outflow is into the liver through the portal vein. I f it was possible to develop an experimental model which diverted the splenic venous blood directly into the systemic circulation, a possible hepatic dependence on the spleen could be revealed. The authors present an attempt to change the flow of the~plenic vein into systemic circulation in the rat. METHODS AND MATERIALS Male Sprague-Dawley rats, weighing 280-320 g, were used for the study. They were kept in a room at constant temperature and fed on a standard rat diet and water. The rats were divided into two groups. In 10 rats, it was tried to perform an end-toside splenocaval shunt. The splenic vein was exposed through a midline incision and was divided close to the portal trunk. The distal end of the splenic vein was anastomosed to the cavaI vein in an end-to-side fashion. For the vascular anastomosis, 9-0 silk atraumatic suture was used and it was performed with the aid of a binocular magnifier with twice diameter magnification. O n the 28th-30th postoperative day, splenoportography was performed to check the patency of the anastomosis. I n the second series of the experiment, 15 rats had a two stage operation. At the first operation, subcutaneous transposition of the spleen was performed. Through a small *Second Department of Surgery, Kyushu University School of Medicine, Fukuoka, Japan. **South Hospital, S-I O0 64 Stockholm, Sweden. * **Department of Surgery, University of Lund, S-221 85 Lund, Sweden. JAPANESEJOURNALOF SURGERY,VOL. 6, No. 4, pp. 184-188, 1976
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incision at t h e left subcostal m a r g i n , the spleen was p u l l e d out a n d fixed u n d e r the skin. T h e a b d o m i n a l muscles were a p p r o x i m a t e d carefully a n d the skin was closed. T h e splenic a r t e r y a n d vein were k e p t intact. O n the 14th p o s t o p e r a t i v e day, a second l a p a r o t o m y was p e r f o r m e d t h r o u g h a m i d l i n e incision a n d the splenic vein was ligated a n d divided. F o u r weeks after the second operation, s p l e n o p o r t o g r a p h y was performed. E t h e r anesthesia was used d u r i n g the o p e r a t i o n a n d the a n g i o g r a p h y . F o r the angiog r a p h y , the contrast m e d i u m , I s o p a q u e C e r e b r a l ( M e g l u m i n e metrizoate, Nyco A / S , N o r w a y ) was used a n d five pictures were taken c o n t i n u o u s l y using an auto film c h a n g i n g system.
Fig. 1.
Splenoportography four weeks after the splenocaval anastomosis. The anastomosis is patent and the inferior caval vein is visualized. However, a big collateral runs into the liver and a big amount of the contrast medium is diverted into the portal system.
186
Saku et al.
Jap. J. Surg. December 1976
RI~,SULTS T h e first series of the e x p e r i m e n t : T e c h n i c a l difficulties with the end-to-side s p l e n o c a v a l shunt were g r e a t a n d t h r e e rats died w i t h i n 24 hours after the o p e r a t i o n . Seven out o f the 10 rats survived a n d were in g o o d conditions after the operation. I n five o f these seven rats, the p o s t o p e r a t i v e s p l e n o p o r t o g r a p h y r e v e a l e d the spleno-caval anastomosis to be o c c l u d e d c o m p l e t e l y a n d new collaterals h a d d e v e l o p e d from the splenic hilus to the liver. T h e rem a i n i n g two rats, h a d o p e n anastomoses. H o w e v e r , despite the p a n t e n c y o f the spleno-caval
Fig. 2.
Splenoportogram from the second series of the experiment. A rich collateral circulation is disclosed around the spleen and all injected contrast medium runs into the systemic circulation through these collaterals.
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187
shunt, new spleno-portal collaterals had developed from the hilus of the spleen to the liver (Fig. 1). The second series of the experiment: All rats survived and were in good condition after the subcutaneous splenic transposition and the ligation of the splenic vein which was performed two weeks after the previous operation. Splenoportography, four weeks after the second operation, revealed a rich net of collaterals from the transposed spleen to the systemic circulation. The contrast medium seemed to leave the spleen by two ways, one originating f r o m the hilus and the other from the convex surface of the spleen. No splenoportal collaterals were disclosed in 13 of the rats and all of the contrast medium was diverted from the liver (Fig. 2). However, in two out of 15 rats, the development of subcutaneous collaterals was rather poor and small collaterals, running into the liver, were visualized. These spleno-portal collaterals were very small and almost all of the contrast medium passed into the systemic circulation. DIsCussION
Since 1946, techniques for making portasystemic shunts in the rat have been described.7, s In 1961, Lee and Fisher 5 performed a direct end-to-side and side-to-side portacaval shunt in the rat usingcontinuous fine vascular sutures. After that, m a n y studies~ have been made about changes of the liver and other organs after portacaval anastomosis. These studies have dealt with diversion of the whole portal venous flow into the systemic circulation but not only the splenic venous flow. To investigate influences of the spleen on the liver, a new experimental model which divert only splenic venous flow into the systemic circulation is requested. The direct end-to-side splenocaval shunt as attempted in the first series of the present study was found to be very difficult in the rat because of the small diameter of the vessels. I f the technical problems could be solved and patent anastomoses obtained, the complete diversion of the splenic venous flow could not be expected because of the newly developed collaterals from the splenic hilus to the liver as evidenced in Fig. 1. This is what we conclude after our first study. We have experiences of the subcutaneous transposition of the spleen since 1970.2, 4 The splenic transposition is an effective method to get collaterals between the spleen and the systemic circulation. On the splenoportography of our previous experiments, rich collateral nets were disclosed from the transposed spleen to the superior and inferior caval systems. The injected contrast medium filled both portal beds and caval systems. The present study demonstrated that the splenic transposition and the additional ligation of the splenic vein had successfully diverted the splenic venous outflow into the systemic circulation. This method is probably the most appropriate experimental model for the requested purpose. The model can be used for studying a possible splenic influence on the liver. ACKNOWLEDGMENT
The present authors would like to express their hearty thanks to Prof. Stig. Bengmark, Department of Surgery, Lund University in Sweden, Prof. Kiyoshi Inokuchi, Second Department of Surgery, Kyushu University and Docent Tord Olin, Department of Radiology, Lund University in Sweden, for their valuable suggestions and for reviewing the manuscript. (Received for publication on July 31, 1976)
188
Saku et ao.
Jap. J. Surg. December 1976
Reference 1. Banff, G. : La Splenomega/ia con cirrosi hepatica, Sperimentale 48: 447-452, 1894. 2. Bengmark, S., B6rjesson, B., Olin, T., Sakuma, S. and Vosmic, J.: Subcutaneous transposition of the spleen - An experimental study in the rat, Scand. J. Gastroent., Suppl. 7: 175-179, 1970. 3. Bengmark, S., B6rjesson, B. and Olin, T.: Development of portasystemic shunts after subcutaneous transposition of the spleen in the rat, Am. J. Surg. 125: 757-762, 1973. 4. Bengmark, S. : Surgical management of portal hypertension, Clinics in Gastroenterology 4: 395-423, 1975.
5. Lee, S.H. and Fisher, B. : Portacaval shunt in the rat, Surgery 50: 668-672, 1961. 6. Lee, S., Chandler, J.G., Broelsch, C.E., Flamant, Y.M. and Orloff, M.J.: Current research review--Portalsystemlc anastomosis in the rat, Or. Surg. Research 17: 53-73, 1974. 7. Reinhardt, W.O. and Bazell, A.H.: One stage functional hepatectomy in the rat, Proc. Soe. Exp. Biol. Med. 62: 270-271, 1961. 8. Whitaker, W.L.: Portal vein ligafion and the Eck fistula in the rat. Proe. Soc. Exp. Biol. Med. 6 1 : 4 2 0 423, 1946.
INTRODUCTION S i n c e Banti 1 first reported an influence of the spleen on the liver in 1894, many investigators have discussed this subject. However, the evaluation of the role of the spleen is hampered by the lack of an appropriate experimental model. There is still no physiological explanation to the fact that the splenic venous outflow is into the liver through the portal vein. I f it was possible to develop an experimental model which diverted the splenic venous blood directly into the systemic circulation, a possible hepatic dependence on the spleen could be revealed. The authors present an attempt to change the flow of the~plenic vein into systemic circulation in the rat. METHODS AND MATERIALS Male Sprague-Dawley rats, weighing 280-320 g, were used for the study. They were kept in a room at constant temperature and fed on a standard rat diet and water. The rats were divided into two groups. In 10 rats, it was tried to perform an end-toside splenocaval shunt. The splenic vein was exposed through a midline incision and was divided close to the portal trunk. The distal end of the splenic vein was anastomosed to the cavaI vein in an end-to-side fashion. For the vascular anastomosis, 9-0 silk atraumatic suture was used and it was performed with the aid of a binocular magnifier with twice diameter magnification. O n the 28th-30th postoperative day, splenoportography was performed to check the patency of the anastomosis. I n the second series of the experiment, 15 rats had a two stage operation. At the first operation, subcutaneous transposition of the spleen was performed. Through a small *Second Department of Surgery, Kyushu University School of Medicine, Fukuoka, Japan. **South Hospital, S-I O0 64 Stockholm, Sweden. * **Department of Surgery, University of Lund, S-221 85 Lund, Sweden. JAPANESEJOURNALOF SURGERY,VOL. 6, No. 4, pp. 184-188, 1976
Volume 6 Number 4
Spleno-systemic Anastomosis in the Rat
185
incision at t h e left subcostal m a r g i n , the spleen was p u l l e d out a n d fixed u n d e r the skin. T h e a b d o m i n a l muscles were a p p r o x i m a t e d carefully a n d the skin was closed. T h e splenic a r t e r y a n d vein were k e p t intact. O n the 14th p o s t o p e r a t i v e day, a second l a p a r o t o m y was p e r f o r m e d t h r o u g h a m i d l i n e incision a n d the splenic vein was ligated a n d divided. F o u r weeks after the second operation, s p l e n o p o r t o g r a p h y was performed. E t h e r anesthesia was used d u r i n g the o p e r a t i o n a n d the a n g i o g r a p h y . F o r the angiog r a p h y , the contrast m e d i u m , I s o p a q u e C e r e b r a l ( M e g l u m i n e metrizoate, Nyco A / S , N o r w a y ) was used a n d five pictures were taken c o n t i n u o u s l y using an auto film c h a n g i n g system.
Fig. 1.
Splenoportography four weeks after the splenocaval anastomosis. The anastomosis is patent and the inferior caval vein is visualized. However, a big collateral runs into the liver and a big amount of the contrast medium is diverted into the portal system.
186
Saku et al.
Jap. J. Surg. December 1976
RI~,SULTS T h e first series of the e x p e r i m e n t : T e c h n i c a l difficulties with the end-to-side s p l e n o c a v a l shunt were g r e a t a n d t h r e e rats died w i t h i n 24 hours after the o p e r a t i o n . Seven out o f the 10 rats survived a n d were in g o o d conditions after the operation. I n five o f these seven rats, the p o s t o p e r a t i v e s p l e n o p o r t o g r a p h y r e v e a l e d the spleno-caval anastomosis to be o c c l u d e d c o m p l e t e l y a n d new collaterals h a d d e v e l o p e d from the splenic hilus to the liver. T h e rem a i n i n g two rats, h a d o p e n anastomoses. H o w e v e r , despite the p a n t e n c y o f the spleno-caval
Fig. 2.
Splenoportogram from the second series of the experiment. A rich collateral circulation is disclosed around the spleen and all injected contrast medium runs into the systemic circulation through these collaterals.
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Spleno-systemie Anastomosis in the Rat
187
shunt, new spleno-portal collaterals had developed from the hilus of the spleen to the liver (Fig. 1). The second series of the experiment: All rats survived and were in good condition after the subcutaneous splenic transposition and the ligation of the splenic vein which was performed two weeks after the previous operation. Splenoportography, four weeks after the second operation, revealed a rich net of collaterals from the transposed spleen to the systemic circulation. The contrast medium seemed to leave the spleen by two ways, one originating f r o m the hilus and the other from the convex surface of the spleen. No splenoportal collaterals were disclosed in 13 of the rats and all of the contrast medium was diverted from the liver (Fig. 2). However, in two out of 15 rats, the development of subcutaneous collaterals was rather poor and small collaterals, running into the liver, were visualized. These spleno-portal collaterals were very small and almost all of the contrast medium passed into the systemic circulation. DIsCussION
Since 1946, techniques for making portasystemic shunts in the rat have been described.7, s In 1961, Lee and Fisher 5 performed a direct end-to-side and side-to-side portacaval shunt in the rat usingcontinuous fine vascular sutures. After that, m a n y studies~ have been made about changes of the liver and other organs after portacaval anastomosis. These studies have dealt with diversion of the whole portal venous flow into the systemic circulation but not only the splenic venous flow. To investigate influences of the spleen on the liver, a new experimental model which divert only splenic venous flow into the systemic circulation is requested. The direct end-to-side splenocaval shunt as attempted in the first series of the present study was found to be very difficult in the rat because of the small diameter of the vessels. I f the technical problems could be solved and patent anastomoses obtained, the complete diversion of the splenic venous flow could not be expected because of the newly developed collaterals from the splenic hilus to the liver as evidenced in Fig. 1. This is what we conclude after our first study. We have experiences of the subcutaneous transposition of the spleen since 1970.2, 4 The splenic transposition is an effective method to get collaterals between the spleen and the systemic circulation. On the splenoportography of our previous experiments, rich collateral nets were disclosed from the transposed spleen to the superior and inferior caval systems. The injected contrast medium filled both portal beds and caval systems. The present study demonstrated that the splenic transposition and the additional ligation of the splenic vein had successfully diverted the splenic venous outflow into the systemic circulation. This method is probably the most appropriate experimental model for the requested purpose. The model can be used for studying a possible splenic influence on the liver. ACKNOWLEDGMENT
The present authors would like to express their hearty thanks to Prof. Stig. Bengmark, Department of Surgery, Lund University in Sweden, Prof. Kiyoshi Inokuchi, Second Department of Surgery, Kyushu University and Docent Tord Olin, Department of Radiology, Lund University in Sweden, for their valuable suggestions and for reviewing the manuscript. (Received for publication on July 31, 1976)
188
Saku et ao.
Jap. J. Surg. December 1976
Reference 1. Banff, G. : La Splenomega/ia con cirrosi hepatica, Sperimentale 48: 447-452, 1894. 2. Bengmark, S., B6rjesson, B., Olin, T., Sakuma, S. and Vosmic, J.: Subcutaneous transposition of the spleen - An experimental study in the rat, Scand. J. Gastroent., Suppl. 7: 175-179, 1970. 3. Bengmark, S., B6rjesson, B. and Olin, T.: Development of portasystemic shunts after subcutaneous transposition of the spleen in the rat, Am. J. Surg. 125: 757-762, 1973. 4. Bengmark, S. : Surgical management of portal hypertension, Clinics in Gastroenterology 4: 395-423, 1975.
5. Lee, S.H. and Fisher, B. : Portacaval shunt in the rat, Surgery 50: 668-672, 1961. 6. Lee, S., Chandler, J.G., Broelsch, C.E., Flamant, Y.M. and Orloff, M.J.: Current research review--Portalsystemlc anastomosis in the rat, Or. Surg. Research 17: 53-73, 1974. 7. Reinhardt, W.O. and Bazell, A.H.: One stage functional hepatectomy in the rat, Proc. Soe. Exp. Biol. Med. 62: 270-271, 1961. 8. Whitaker, W.L.: Portal vein ligafion and the Eck fistula in the rat. Proe. Soc. Exp. Biol. Med. 6 1 : 4 2 0 423, 1946.
