The investigation of cases suspected of stone is concerned with (1) those in which a shadow is visible and (2) those in which X-rays throw no shadow.In the former group the nature of the shadow must be determined. If a stone, it must be accurately placed in the urinary tract and the anatomy and function of the affected and unaffected parts of the tract must be determined.A stone may be recognized by the characteristic shape to which it grows in the pelvis, in a calyx or in the ureter. In the earlier stages, or when the shape of the shadow is not characteristic, radiograms may be made on inspiration and expiration. In orthopædic and other cases immobilized for long periods interesting calculi may form and may subsequently be disintegrated and passed, or may require surgical treatment.For stones in the kidney and upper ureter pyelography by the descending route is ideal. For infected stones the retrograde route is preferable. For small ureteric stones an opaque catheter is best.Non-opaque stones are of real surgical significance. It is essential to make a positive diagnosis in a case of suspected stone, even if operation is not required. Furthermore, non-opaque stones are sometimes sufficiently large to demand operative removal. The presence of these stones can be inferred from descending pyelograms, and the stones themselves can be displayed by means of the opaque material they pick up in the course of a descending pyelography.
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