Subjects (n=149) underwent ultrasound imaging at 25 clinical sites; one subject's ultrasound was non-diagnostic for all organs. A small number of sonograms were technically inadequate for assessment of some individual organs, resulting in a slightly variable number of measurements for different abdominal organs. Of the 148 with adequate imaging, the mean age was 13.0 years (range 5–19 years, median 13.3 years), 77 were boys, 147 had HbSS sickle cell disease, and 1 had Hb S-β° thalassemia. The average length of time on transfusion therapy was 7.0 ± 3.7 years (range 1.8 – 15.5 years; median 6.6 years).
For 2 subjects the sonograms were of non-diagnostic quality for spleen assessment. In the remaining 146 subjects the spleen was sonographically visible in 115 and not visible in 31 (31/146, 21%). Children with visible spleens had average splenic volumes of 283.7 mL ± 200.7 mL; many had large spleens including 29 (29/115, 25%) with spleen volumes between 300 and 500 mL and another 15 (15/115, 13%) with volumes > 500 mL. Larger spleen volume was significantly correlated with a lower platelet count (r = −0.319, p =0.001). There was no association between sonographically non-visible spleen and age at index stroke (p = 0.931). Subjects with non-visible spleens had significantly higher mean ALT levels (78 ± 64 IU/L vs. 51 ± 28 IU/L; p = 0.004) and significantly higher LIC values (mean = 19.4 ± 10.9 mg Fe/g liver dry weight vs. 14.2 ± 8.6 mg Fe/g liver dry weight; p = 0.021) than those with visible spleens. Subjects with a history of splenic sequestration and sonographically visible spleens had significantly smaller spleen volumes (n = 11, mean volume = 139.1 ± 94.3 mL) than those without history of sequestration (n = 103, mean volume = 299.2 ± 203.2 mL; p <0.001).
Sonographic spleen length was strongly correlated with spleen volume (r = 0.945, p < 0.001). There was no significant difference in the average sonographic spleen lengths of subjects enrolled in the SWiTCH trial compared with age-matched hematologically normal children (). Abnormal splenic echotexture was observed in 24 of 115 (24/115, 21%) visible spleens including inhomogenous splenic echotexture (n = 15), coarse echotexture (n = 3), echogenic echotexture (n = 3), round hypoechoic splenic foci (n = 2) and a round hyperechoic focus (n = 1). Subjects with inhomogenous spleens had a longer duration of transfusion therapy (mean duration 8.2 ± 3.3 yrs vs. 6.3 ± 3.6 yrs; p = 0.056) and higher prevalence of alloantibodies (50% vs. 24%, p = 0.039) than those with homogenous spleens. There was also a significant association between inhomogenous spleens and older age at enrollment (mean age, 14.6 ± 3.2 years vs. 12.1 ± 4.0 years; p = 0.023) and higher LIC (mean LIC 18.6 ± 8.1 mg Fe/g liver dry weight vs. 13.6 ± 8.6 mg Fe/g liver dry weight; p = 0.024). There was no relationship between spleen inhomogeneity and age at index stroke (p = 0.229). There was no clustering of abnormal spleen findings with other organ abnormalities, and no correlations were identified with either LIC or transfusion duration.
Table I Comparison of spleen lengths of subjects enrolled in the SWiTCH trial and published age-matched hematologically normal children 
Twenty-three subjects had documented prior surgical splenectomy; three of these subjects had sonographically visible spleens that were felt to represent re-growth of accessory spleens, and two had sonograms that were inadequate for spleen assessment. Therefore, of the 31 subjects with non-visible spleens, 19 (19/31, 61%) had undergone splenectomy and 12 (12/31, 39%) had no reported history of splenectomy, so were considered to have splenic autoinfarction. Seventeen of the 23 surgical splenectomies occurred while subjects were receiving chronic transfusions and were performed for the following indications: splenomegaly and hypersplenism (n = 15), autoimmune hemolytic anemia (n = 1), and unknown (n = 1). Five splenectomies occurred prior to transfusion therapy, all for splenic sequestration, but the timing of one splenectomy was unknown.
A total of 148 subjects had adequate renal imaging. There was a strong correlation between renal lengths and volumes (right kidney, r = 0.85, p < 0.001; left kidney, r = 0.84, p < 0.001). As expected, greater patient age, height and weight were correlated with increased renal volume (age; r = 0.72, p < 0.001: height; r = 0.75, p < 0.001: weight; r = 0.75, p < 0.001). Renal lengths of subjects enrolled in the SWiTCH trial were significantly larger than age matched published normal values (). There was no significant association between history of hypertension (n = 8) and renal volume (p = 0.30). Four subjects had echogenic kidneys, 3 had loss of renal corticomedullary differentiation and one had a simple renal cyst. There was no clustering of abnormal kidney findings with other organ abnormalities, and no correlations were identified with either LIC or transfusion duration.
Table II Comparison of renal lengths of subjects enrolled in the SWiTCH trial and published age-matched hematologically normal children 
Similarly, 148 subjects had adequate biliary imaging and 99 (99/148, 67%) had abnormal findings consistent with gallbladder disease: 37 (37/148, 25%) had undergone prior cholecystectomy, and 46 of the remaining 111 (46/111, 41%) had gallstones and another 16 (16/111, 14%) had gallbladder sludge. Additional abnormal biliary findings included common bile duct (CBD) dilatation in 8 (8/111; 7%) and gallbladder wall thickening in 3 (3/111; 3%). The presence of gallbladder disease (prior cholecystectomy, current gallstones or sludge) was significantly associated with older age at enrollment (mean 13.8 ± 3.7 years vs. 11.8 ± 4.0 years; p = 0.002), greater liver length measured on ultrasound (mean 159 ± 21 vs. 142 ± 21 mm; p < 0.001), longer duration of transfusion therapy (mean 7.6 ± 3.6 years vs. 6.3 ± 3.8 years; p = 0.034) and higher total serum bilirubin (mean 3.8 ± 2.5 mg/dL vs. 2.5 ± 1.1 mg/dL; p < 0.001). Gallbladder disease was not associated with serum ALT, AST, erythrocyte alloantibodies or autoantibodies, type of transfusion (erythrocytapheresis, partial exchange or simple), palpable hepatomegaly, or history of liver disease (all p ≥ 0.070). Subjects enrolled in the SWiTCH trial had significantly larger, sonographically measured liver lengths than published values for age-matched normal children ().
Table III Comparison of liver length of subjects enrolled in the SWiTCH trial and published values for hematologically normal children