Effect of plasma proteins and temperature on echogenicity of blood.

An explanation is proposed for the echogenicity to ultrasound scanning at 5 mHz and above of unclotted blood under conditions of stasis. In vitro experiments using blood from normal subjects and from patients with myeloma revealed that: 1) lysis of red cells prevented echogenicity, 2) echogenicity increased with increasing hematocrit, fibrinogen and other macromolecules, and temperature, and 3) blood from myeloma patients showed increased echogenicity and rouleau formation, a form of aggregation seen on peripheral smears. From these experiments it was concluded that red cell aggregation is a major cause of echogenicity of unclotted blood, requiring both intact red cells and conditions which are known to enhance red cell aggregation, such as the presence of macromolecules and increased temperature.