(In each case the lower border is referred to.)
• L1: the transpyloricplane (of Addison). This horizontal plane passes approximately through the tip of the 9th costal cartilage, the pylorus, pancreatic neck, duodenojejunal flexure, the gall-bladder fundus and the hila of the kidneys. This plane also corresponds to the level at which the spinal cord terminates and the lateral edge of rectus abdominis crosses the costal margin.
• L2: the subcostal plane. This plane corresponds to a line joining the lowest points of the thoracic cage—the lower margin of the 10th rib laterally.
• L3: the level of the umbilicus (in a young slim person).
• L4: the transtubercular plane. This corresponds to a line which joins the tubercles of the iliac crests.
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