Measuring the length of C-P and C-PS. We took the point landing on the line from midpoint of superior margin of the pubic symphysis to the lower point of sacroiliac joint (P-S) as M point. M point was on one third the length of P-S closer to superior margin of pubic symphysis. C-PS was the length from central kidney point to M point. C-P was the length from central kidney point to superior margin of pubic symphysis. ♦: The central kidney point, defined as the midpoint of the long axis of kidney. ∆: The lower point of sacroiliac joint. ▲: The midpoint of superior margin of the pubic symphysis.