病位在上... \ ...病位在下...
http://www.360doc.com/content/090627/09/139068_4047070.html

It refers to location of the disease, practically dividing the body into upper & lower half ( transverse plane)

The transverse plane (also called the horizontal plane, axial plane, or transaxial plane) is an imaginary plane that divides the body into superior and inferior parts.
http://en.wikipedia.org/wiki/Transverse_plane


suggestions:
病在上 : diseases located above the transverse plane or disease in the superior region or upper half of body
病在下 : diseases located below the transverse plane or diseases in the inferior region or lower half of body