Splenomegaly and red blood cell destruction: a morphometric study on the human spleen.

Abstract

In looking for morphologically determinable characteristics of hypersplenism a quantitative analysis of histological and cytological splenic structures with cardiac and portal congestion, splenic vein thrombosis and hereditary spherocytosis was carried out. The centre of the investigation was the red pulp, which with its complexly structured sinus and pulp cord system, richly equipped with actively phagocytic cells, represents the main scene of normal and pathologically increased intrasplenic blood cell destruction. The following structures were quantitatively recorded: percentage volume proportion and total volume of red pulp, white pulp, trabeculae and blood vessels; percentage volume proportion and total volume of sinus, pulp cords and capillaries. We also calculated the length, the mean sectional area and the mean surface area of the sinus system. Finally we determined the sinus lining cell, reticular cell, macrophage and blood monocyte content of the red pulp. We came to the following results : 1. a) With increased destruction of normal blood cells resulting from impairment of venous blood flow in the portal vein and splenic vein areas, the volume of the red pulp is increased primarily as a result of considerable enlargement of the sinus volume compared to the norm. Here the mean sinus sectional area mostly becomes smaller, but the total sinus length is increased by as much as 14 times the norm. The lengthening of the sinus system is based not so much on a stretching of pre-existent sinus as on a new formation of mostly very narrow sinus branches and anastomoses. The number of sinus lining cells per cm2 of the sinus surface is decreased, possibly as a result of a discrepancy between new sinus constructions and sinus lining cell proliferation. The total number of actively phagocytic splenic cells, particularly reticular cells in the pulp cords, is considerably higher. b) Increased intrasplenic destruction of abnormal blood cells, e.g. in hereditary spherocytosis, leads to a widening and increase of the pulp cords, a lengthening of the sinus system and an increase of phagocytically active cells as well as hyperplasia of the sinus lining cells. 2. The quantitative morphological findings produce the following functional interpretations : The volume increase of red pulp means an often considerable expansion of the storage capacity of the spleen for blood cells. The blood circulation becomes slower as a result of the great anastomisation of the sinus system, which again leads to disturbance of the flow properties of the blood. The blood cells form aggregates and remain in the pulp cords, where they become conditioned by the very unsuitable metabolic circumstances for phagocytosis by the numerous reticular cells.