The document discusses various topics related to pediatric radiology: - Fetal kidney lobulation seen on ultrasound as indentations overlying the space between pyramids. - Complete duplication of the urinary tract is more often associated with reflux in the lower pole system than the upper pole system. - Langerhans cell histiocytosis manifests as vertebra plana due to proliferation of histiocytes. - Ewing sarcoma rarely occurs before age 5 years.