Splenic circulatory dynamics were studied in 19 patients, 12 of whom had congestive splenomegaly. In 10 patients with markedly enlarged congested spleens (spleen weight > 600 g), the spleen represented > 1% of body weight and was associated with an enlarged (> 8 mm diameter) tortuous splenic artery and rapid splenic arterial flow (1191 ± 177 ml/min or 118 ± 17 ml/min per 100 g spleen). Cross clamping of the splenic artery reduced portal system pressure (26.7 ± 2.6 mm Hg to 19.0 ± 1.6 mm Hg). On the other hand, in 9 patients with minimally enlarged congested spleens (spleen weight < 300 g) or noncongested spleens, the spleen represented < 1% body weight, the splenic artery was < 6 mm diameter, and splenic arterial flow was only 175 ± 25 ml/min (64 ± 4.0 ml/min per 100 g spleen) or 112 ± 12 ml/min (47 ± 6.2 ml/min per 100 g spleen), respectively. Splenic size (weight) in patients with congestive splenomegaly correlated with the rate of splenic arterial flow (r = 0.86, P < 0.01), but not to level of portal pressure (r = 0.20, P > 0.50). In all patients, splenic venous oxygen saturation was high (mean, approximately 90%). These findings indicate that splenic enlargement in patients with congestive splenomegaly is proportional to splenic arterial inflow, whereas elevated splenic venous pressure derives not only from increased resistance to splenic venous outflow, but also from increased splenic arterial inflow. Splenic venous oxygen saturation is high with or without splenomegaly, and therefore cannot be invoked as evidence of pathological arteriovenous shunting.
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