Small Spleen

Variants, “Aged Spleen”

Functional Hyposplenism/Asplenia

Sonographic determination of a longitudinal diameter less than 11 cm and a thickness less than 5 cm should be recorded and documented as a “small” spleen (Fig. 5.25).

To date, this finding has been regarded as a variant and certainly does not seem to be of any clinical consequence in most cases. Spleen size varies with the type of patient, and the volume of the organ also decreases with age. On colorflow Doppler scanning, these spleens will be visualized with a normal fanlike vasculature of the parenchyma. At present, it is unknown whether this age-dependent decrease in spleen size has any functional significance.

Fig. 5.25 Small spleen in a 75-year-old patient, possibly corresponding to an “aged spleen.” PE = pleural exudation.

In recent years functional autosplenectomy syndromes have increasingly been reported in sickle-cell anemia ( 5.2a), after extensive splenic trauma and septic disease, in autoimmune disease ( 5.2b,c), as a result of Thorotrast exposure of the spleen, and particularly following allogeneic bone marrow transplantation as a complication of chronic graft-versus- host disease (GVHD) ( 5.2 d–f, Table 5.2).

Apart from the clinical symptoms, the principal sonographic sign of functional splenic changes is the diminishing size of the spleen ( 5.2 g–i). The findings in color-flow Doppler scanning vary. Although in some cases there is no vascularization whatsoever, most organs will demonstrate a rarefied vascular bed. However, sonographic confirmation of splenic blood flow cannot rule out functional asplenia. This requires additional functional studies of the spleen (technetium-99 m [99 mTc] sulfur colloid labeling, platelet count, demonstration of Howell–Jolly bodies).

Table 5.2 Possible causes of functional hyposplenism/asplenia

In individual cases functional asplenia is characterized by reduced contrast enhancement ( Fig. 5.2j–l).

Bone marrow transplantation (GVHD)

d–f Acute leukemia.

d Normal-sized spleen before bone marrow transplantation.

Color duplex ultrasound and CEUS

e Shrunken spleen after allogeneic bone marrow transplantation in severe GVHD.

f Colloid-labeled scintiscan: the spleen is barely visible, indicating functional hyposplenism.