[Extent of natural variation of the longitudinal axis of the kidney collecting system].

Since the position of the longitudinal axis of the renal pelvis is of special significance in the diagnosis of the renal masses, the physiological range of the angle formed by this axis and the spine was determined by retrospective evaluation of 516 urograms. Up to the age of 11, in boys and girls the angle increases without side difference. In the adult, the position of the kidney is more transverse in men than in women, the left angle being smaller than the right one in both, male and female. The lateral contour of psoas muscle changes in similar fashion except for the side difference. Moreover, the decrease in size of the adrenal glands in early childhood is thought to be responsible for the rotation of the kidneys. Neither the kidney's shape nor its position respective to the spine proved significant for the position of the axis. The right kidney constantly being in a position nearly one vertebra lower than the left one, both sink caudad about 2/3 of a vertebra after the age of 50.