Partial Splenectomy, Transposition of the Spleen to the Abdominal Wall or Splenohepatoplasty in Portal Hypertensive Rats. Effects on Portal Venous Pressure and Homeostasis - Microscopical Appearance of the Transposed Spleen

Abstract

Reduction of the splenic volume by partial resection and collateral development after transposition are of potential value in the elective treatment of esophageal varices, hypersplenism and ascites. A study was performed on young Wistar rats. A simple animal model of extrahepatic portal hypertension was used, narrowing the portal vein to an outer diameter of one millimeter (PVS). One day, three weeks and seven weeks after this operation the portal venous pressure was elevated as compared with the sham-operated controls. The portal hypertension was statistically significant at week three (1.31 +/- 0.04 vs. 0.72 +/- 0.18 kPa, p = 0.01). Portocaval pressure gradient after partial resection of the spleen (SR) and intramuscular transposition (IMTrans) was compared with the pressure gradient after graded portal vein stenosis. Three weeks after intramuscular transposition portocaval pressure gradient was reduced (1.46 +/- 0.38 vs. 1.74 +/- 0.13 kPa, n.s.). This data supports the hypothesis that the portal venous high-pressure compartment and the systemic venous low-pressure compartment are maintained after development of natural shunts to the systemic circulation. In the following experiment different types of splenic transposition were tested and compared to each other and a normal control group or to rats with protal vein stenosis (PVS), respectively. After PVS, the animals were reoperated, an SR was performed and the wound surface of the spleen was transposed into the left abdominal wall subcutaneously (SCTrans) or intramuscularly (IMTrans) or to the left liver lobe (splenohepatoplasty, SHP), respectively. After three weeks the animals underwent measurements of organ weights, collections of blood samples and the spleen was investigated histologically. Blood cell counts were nearly normal but total serum protein, albumin and the colloid osmotic pressure were slightly diminished or significantly reduced (COP in the groups PVS + SR + IMTrans or SCTrans, p < 0.05) compared to the controls. Differences to the group with portal vein stenosis (PVS) were not significant. Serum protein electrophoresis after splenic transposition revealed an unobtrusive distribution pattern. Animals after SHP had the best increase in weight and high protein levels, but splenohepatic collateral development seemed sparse. Differences of plasma ammonium levels were statistically not significant, but some animals had elevated levels after transposition. Morphometry of routine-stained spleen specimens showed an intact immunoarchitecture of the transposed spleens.