1. The kidney may be damaged by disease:

• One possibility is that the glomerulus can be damaged by immune mechanisms resulting from bacterial invasion or an autoimmune disease like "systemic lupus erythematosus". Antigen-antibody complexes become trapped in the glomerulus because of their large size. Capillaries may become clogged or compressed, preventing blood flow. Look here to see what can happen!

2. Dialysis may provide a solution until the kidney recovers or is replaced by a transplant.

• Dialysis is a simple process that takes solute initially in a small volume V₁ and dilutes it into a larger volume V₂.

• Hemodialysis machines continually flow solvent through the machine, effectively making the compartment with volume V₂ infinite.

• A hemodialysis machine puts a semipermeable membrane with permeability p and area A between two compartments with volumes V₁ (human) and V₂(machine):
  

  The volume V₁ is the effective blood volume of the person. The actual blood volume in the average human is about 4.5 l. However, this is in equilibrium with the interstitial fluid surrounding the cells and the water in cells. So, the effective blood volume is actual blood volume plus volume of interstitial fluid and cells for a total of about 30 to 40 l, which represents about 63% of body weight in human males and 52% in females. We will flow dialysis fluid through our apparatus, so the effective volume V₁ is effectively infinite.

• In class, I'll go through some calculations using the permeabilities of common waste products found in the human blood to calculate the times required for dialysis to be effective. (You will need to be in class, or to understand the material from discussion with your colleagues, to follow these calculations.)

All text and images, not attributed to others, including course examinations and sample questions, are Copyright, 2006, Thomas J. Herbert and may not be used for any commercial purpose without the express written permission of Thomas J. Herbert.