The small spleen: sonographic patterns of functional hyposplenia or asplenia

Functional hyposplenia or asplenia (FAS) can be associated with potential fatal infections. The diagnosis of FAS is traditionally made on liver-spleen scintigraphy and finding Howell-Jolly bodies within erythrocytes. In this retrospective study, our goal was to identify any characteristic sonographic findings of the spleen in patients with FAS in an attempt to determine whether the diagnosis of FAS can be made sonographically.

In a review of all medical and sonographic records from the period of January 1, 1985, through December 31, 2001, we identified 24 patients (11 men, 13 women) in whom FAS had been diagnosed by liver-spleen scintigraphy (n = 13) or the finding of Howell-Jolly bodies (n = 11). The following sonographic parameters were determined: size of spleen (small, normal, or large), echotexture of the spleen (homogeneous versus inhomogeneous), echogenicity (isoechoic versus hyperechoic), presence of focal splenic lesions, and patterns of splenic vascularization as determined by color Doppler sonography (absent flow, hilar flow, or parenchymal flow).

The spleen was small in 20 patients (83%) and normal in the other 4 (17%). Echotexture was homogeneous in 13 patients (54%) and inhomogeneous in 11 (46%). The spleen was isoechoic in 18 cases (75%) and hyperechoic in 6 (25%). Six patients (25%) had focal lesions. Color Doppler sonography showed absent flow in 4 patients (17%), hilar flow in 17 (71%), and hilar and parenchymal vascularization in 3 (12%).

Sonographic findings in the spleen of patients with FAS are characterized predominantly by a small spleen with absence of parenchymal vascularization on color Doppler sonography in most cases. Future prospective studies will be necessary to confirm these findings and to determine whether FAS can be diagnosed reliably with sonography.