Robert L. Lebowitz, M.D. Children' s Hospital, Harvard Medical School Boston, Massachusetts

This 9-year-old boy presented with left flank pain and hematuria. The plain films, obtained before the IVP, showed a stone in the region of the left kidney (arrow) and also several stones in the distral left ureter (arrow). The right femoral head and neck were noticeably more lucent than the left head and neck. The IVP showed left obstruction and hydroureteronephrosis down to the level of the ureteral stone. He had fractured his right femur some months before and had been immobilized for several weeks. He was still not bearing weight normally on his right leg. This is an example of a stone that developed during immobilization, and the clue on the plain film is the lucency of the right proximal femur.