A ATUDY ON THE PATHOGENESIS OF SPLENOMEGALY IN PORTAL HYPERTENSION

Abstract

Though splenomegaly is one of the common manifestations in portal hypertension, the pathogenesis in the developement of splenomegaly remains unclear. An attention was forcused to investigate the intrasplenic pressure as an index of intrasplenic circulation, and the histological characteristics of the spleen.
Since 1960, Prof. Imanaga has proposed a classification of portal hypertension according to the state of intrahepatic circulation as follows;
Group I Extrahepatic obstruction of the portal vein
Group II Intrahepatic obstruction of the portal vein
Group III Intrahepatic obstruction of
1) hepatic vein
2) hepatic and portal veins
Group IV Extrahepatic obstruction of the hepatic vein
An observation was carried out on 77 cases including 10 normal and 67 enlarged spleens who belonged to Group II and Group 111-2 but some cases.
The spleen biopsies, measurement of portal and intrasplenic pressure were examined and the findinge were compared with the state of intrasplenic circulation.
The results obtained were as follows;
1) The intrasplenic pressure was always higher than the portal pressure but one exception. In almost all cases the intrasplenic pressure was proportional to the elevated portal preure; i) the intrasplenic pressure elevated with an average of 383mmH₂O, the portal pressure also elavated with an average of 350mmH₂O in 30 cases of Group II, ii) the intrasplenic pressure elevated with an average of 404mmH₂O, the portal pressure also elevated with an average of 372mmH₂O in 30 cases of Group 111-2.
2) Elevated portal preseure was reduced to the normal level and the enlarged spleen decreased in size after end-to-side portacaval anastomosis. In such cases the intrasplenic pressure was also reduced remarkably; i) the intrasplenic pressure was depressed to an average of 214mmH₂O in 19 cases of Group II, and ii) in 16 cases of Group 111-2 the pressure also was depressed to an average of 219mmH₂O.
3) Histological characteristics of the spleen with portal hypertension were divided into two types; “reticulofibrosis” and “fibroreticulosis”. In Group II the reticulofibrosistype was found in 67 per cent of the patients, whereas in Group III-2 with cirrhosis the fibroreticulosistype was noticed in 73 per cent of the patients.
However, since there were many indifinite types of these histological alterations in both group, any definite pathogenesis in the development of splenomegaly was not demonstrated on the ground of these histological findings, as to whe ther the enlarged spleen be as primary or secondary.
4) The histological findings, i. e. the grade of fibrosis and sinushyperplasia, were considerably correlated with the grade of elavated intrasplenic pressure.
In conclusion, the results obtained led us to suggest that elevated portal pressure due to intrahepatic obstruction of the portal vein may primarily play a role in the development of splenomegaly.