Kidney Failure

What happens if kidneys fail completely?

Concentrations of urea and mineral ions build up

Loss of electrolyte balance

If kidneys fail:

• Body cannot excrete excess Na+, K+, Cl- ions

• Causes osmotic imbalances in tissues & eventual death

  • Decreased water in cells

Built up urea

If kidneys fail:

• Body cannot get rid of urea

• Can poison cells ; is toxic

High blood pressure

Kidneys maintain water balance, so help control b.p. If kidneys fail:

• B.p. increases

• Positive feedback w. increased ions in blood

• Can lead to heart problems & strokes

Weakened bones

Calcium/phosphorous balance in blood is lost 

Joints

Pain and stiff

• Due to abnormal proteins build up in blood

Anaemia and RBC production

• No erythropoietin hormone to stimulate RBC production

• Leads anaemia, being lethargic and tired

What is GFR

Glomerular Filtration Rate

• Used to determine kidney disease

How is GFR determined

Blood test measures level of creatinine in blood

• Is a breakdown product of muscles ; used to give estimation

If levels go up, kidneys not working properly 

What factors need to be taken into account when working out GFR?

1. GFR decreases w. age

2. Men usually have more muscle mass and so more creatinine than women 

2 ways to treat kidney failure

1. Renal dialysis (Haemodialysis)

2. Transplant

Haemodialysis 

• Dialysis machine 

• Usually in hospitals - some have at home

• Has to be repeated regularly , takes 8 hrs

• Need to manage diets carefully (little protein & salts)

• Is readily available

• Expensive

• Depends on diffusion down conc. gradients

How does haemodialysis work?

• Blood leaves patient’s body from artery & flows in thru partially permeable dialysis membranes

  • Mimics basement membrane of B.C.

• Contains normal plasma levels of glucose & mineral ions so no net movement of g out of blood

  • Excess mineral ions move down conc. g by diffusion

• Contains no urea

  • Steep conc. gradient, much leaves blood

• Blood & dialysis flow in opp. directions to maintain counter current exchange system & maximise exchange

How does transplant work?

• Blood vessels are joined and ureter of new kidney is inserted into bladder

• If successful, kidney will function for many years

Transplant

• Risk of rejection

  • Antigens on donor differ from antigens on recipient’s cells 

  • Match as close as possible (tissue type)

• Immunosuppressants 

  • Helps prevent rejection

  • Prevent effective responses to new infectious diseases

• Don’t need to diet, or go to regular, long dialysis sessions

• Shortage of donors