Use of radionuclide scanning to estimate size of spleen in vivo.

Splenic ultrasound was performed and spleen scans obtained by a rectilinear scanner after injection of In-113m-labelled heat damaged red cells on 14 patients with various haematological disorders. Correlation was assessed between the measured volume of the operatively removed spleens, their volumes as calculated from the ultrasound data, and their preoperative dimensions of length, circumference, and area on the scans. The relation of scan to volume was best defined by an equation V = 9.88A - 534, where V = volume of spleen (cm3) and A = area (cm2) on posterior scan. The mean percentage difference between calculated and actual spleen volume was 0.2 (SD 6.7)%. Average spleen density was established as 1.04 g/cm3. The formula was shown to be reliable in the range of splenic area c 73-450 cm2--that is, volume c 185-4000 cm3. This range includes the average normal sized spleens and the splenomegalies that are most often found in clinical practice. The formula is not valid when the spleen is smaller than normal. As the method depends on measurement of the spleen image shown by scintigraphs, it cannot be used when there is functional asplenia.