This section is from the book "Applied Anatomy: The Construction Of The Human Body", by Gwilym G. Davis. Also available from Amazon: Applied anatomy: The construction of the human body.
The kidneys when normal are about 12 cm. (4 1/2 in.) long, 6 cm. (2 1/2 in.) broad and 3 cm. (1 1/4 in.) thick. The right is the thicker and the left a little the longer.
They lie in the lumbar regions under the lower portion of the thoracic wall. Their upper ends are nearer the midline than the lower and the inner edges point forward and inward, thus one surface is antero-external and the other posterointernal.
Viewed posteriorly the right kidney has its upper edge opposite the eleventh dorsal spine and the lower edge of the eleventh rib. Its lower edge is opposite the upper edges of the third lumbar spine and vertebral body and about 4 cm. (1 1/2 in.) above the highest point of the crest of the ileum, which is opposite the fourth spine (Fig. 433). The left kidney is usually 1.25 cm. (1/2 in.) higher, but being a little longer than the right, its lower limit may not be quite that much higher. The kidney is slightly lower in women and children than in men. The inner border reaches 10 cm. (4 in. ) and the hilum 4 to 5 cm. (1 1/2 to 2 in.) from the median line, the latter being in front of the interval between the first and second lumbar spines (H. J. Stiles). Viewed anteriorly, the lower edge of the right kidney is 2.5 cm (1 in.) above a transverse line through the umbilicus, the left being a little higher. The upper edge is opposite approximately the tip of the ensiform cartilage. The upper end approaches within 3 cm. (1 1/4 in.) of the median line. About two-thirds of the kidney lies to the inner side and one-third to the outer of a line drawn longitudinally through the middle of Poupart's ligament. The hilum would be 4 to 5 cm. (1 1/2 to 2 in.) out from the middle of a line joining the upper extremities of the two semilunar lines.
The posterior surface at its upper portion rests on the diaphragm; beneath, its lower portion, from within out, rests on the psoas, quadratus lumborum, and transversalis muscles. Between the kidney and the quadratus lum-borum run the last thoracic, the iliohypogastric, and the ilio-inguinal nerves. The transversalis fascia as it leaves the body of the first lumbar vertebra arches over the psoas muscle, forming the internal arcuate ligament, and is attached to the transverse process of the first lumbar vertebra. It then proceeds out over the quadratus lumborum to be attached to the outer portion of the twelfth rib, forming the external arcuate ligament. It then blends with the tendon or fascia, giving origin to the internal oblique and transversalis muscles. Between the fibres of the diaphragm which arise from the external arcuate ligament - over the quadratus lumborum muscle - and the fibres arising from the twelfth rib, a triangular space exists with its base downward. It is called the hiatus and if marked allows the pleura and the kidney to come in contact without any muscular fibres intervening. This favors the passage of pus from the region of the kidney into the pleural cavity and lung.
The anterior surface relations differ on the two sides. On the right side above is the suprarenal gland, then a large area where it is in contact with the liver, then below to the inner side the descending or second part of the duodenum, and below and to the outer side the hepatic flexure of the colon. On the left side above and to the inner side is the left suprarenal gland. Beneath it is a small area for the stomach, and still lower a larger one for the left end of the pancreas. On the outer portion of the anterior surface is an area for the spleen and below one for the splenic flexure of the colon and jejunum.
The hilum is the name given to the notch in the inner edge of the kidney. It contains the pelvis and commencement of the ureter and the renal vessels and nerves. The sinus is the cavity of the kidney. The edges of the pelvis are attached to the borders, or rim, of the hilum.