Initially the metanephric kidneys are located in the pelvis in front of the developing sacrum. The two kidneys lie quite close to ea9h other and their hilar
regions face ventrally. Between the 6th and 9th weeks the kidneys undergo positional changes, which involve ascent and rotation.
Ascent of the kidneys. The kidneys gradually ascend from the pelvis into the abdomen and also move away from each other. By the 9th week the kidneys reach their adult position in the lumbar region just under the developing suprarenal glands. The ascent of the kidneys results mainly from rapid growth of the caudal part (ie, the lumbosocral region) of the embryonic body. The ascent of the kidney is necessarily associated with an elongation of the ureter.
Rotation of the kidneys. During its ascent, each kidney undergoes a rotation of 90 degree, so that the renal hilum comes to face medially and the original posterior border becomes the convex lateral border of the kidney.