Different mechanisms affect the heterogeneity in children and adults. Donnelly et al looked at transient splenic heterogeneity and the variables that affect it in children.
They found transient splenic heterogeneity in about 70% of children. This was maximally visualuzed at ~25 seconds and resolved by 70 seconds in the majority (95%) of cases.
They also found that faster rates of contrast injection (≥ 1.0 cc/sec) were more likely to be associated with transient splenic heterogeneity. The time of visualization and time to resolution, however, did not seem to be affected by the rate of injection.
Children older than 1 year were also more likely to have transient splenic heterogeneity, which was thought to be related to the increasing ratio of white pulp (lymphoid follicles) to red pulp (vascular sinusoids) during the first year of life.
The image above is from a 10-year-old boy. The arterial phase reveals the archiform pattern of enhancement, which resolves on the venous phase image.