1. Splenic blood flow and splanchnic haemodynamics have been studied in twenty patients with splenomegaly due to blood dyscrasia or diseases involving the reticuloendothelial system. Thirteen of these patients had portal hypertension, three had abdominal collaterals on arteriovenography and one oesophageal varices.
2. Total spleen blood flow was increased in all with values up to 1550 ml/min, and associated with this liver blood flows increased up to 2·61 1 min−1 m−2. In four patients the cardiac output was raised.
3. In five patients a raised wedged hepatic vein pressure was found which was solely related to the increase in liver blood flow, but in two others, in whom hepatic histology was abnormal, there was also an increase in postsinusoidal resistance. Nine patients had a raised hepatic pre-sinusoidal resistance. This was related to a greatly increased liver blood flow with portal tract fibrosis and cellular infiltration as possible additional factors.
4. The haemodynamic findings in these patients were similar to those found previously in patients with tropical splenomegaly. In both groups spleen blood flow in ml 100 g−1 min−1 was inversely proportional to spleen size. There were similar increases in total spleen and liver blood flows and in the percentage of patients with an increased pre-sinusoidal resistance. In contrast, in cirrhosis there was no inverse relationship between flow in 1 100 g−1 min−1, and of spleen size, and for the degree of splenomegaly total spleen blood flow was relatively greater.