Kidney Failure Flashcards
What are the 5 main factors which may cause the kidneys to stop functioning normally
1) kidney infections = can damage the basement membrane/ podocytes/ kidney tubules
2) kidney stones = sharp structures which can directly damage kidney tissue
3) high blood pressure = can damage the basement membrane and affect ultrafiltration process
4) physical injury = could rupture the kidney
5) genetic conditions = e.g polycystic kidney disease
What are the 4 main problems caused by reduced kidney functioning/ failure?
1) if the ultrafiltration mechanism is affected, substances which should stay in the blood may end up in the urine e.g red/ white blood cells, large plasma proteins
2) if kidney function fails completely = build up of toxic urea in the blood
3) disrupted electrolyte balance of blood plasma proteins
4) changes to blood pressure = kidneys usually regulate blood water content, which in turn affects blood pressure
What is the GMR (Glomerulus filtration rate)
-the rate at which substances are filtered out of the blood in the glomerulus into the renal capsule
-a rate of filtration below the normal acceptable range indicates that the kidneys are not functioning properly
How is ultrafiltration rate measured (indirectly)?
-a blood test measures the concentration of creatinine in the blood. This is a breakdown product from muscle cells, and us usually filtered out by the kidneys
-if the concentration of creatinine in the blood increases, this is an indication that the kidneys are not working properly
-the units for GFR are cm3min-1
What factors need to be taken into account when estimating GFR?
-age (gradual decline in GFR)
-gender (males have more muscles, so higher levels of creatinine)
-fitness levels (more active people tend to have more muscle tissue, so higher levels of creatinine)
What GFR reading suggests kidney failure?
-below 15 = kidneys are filtering so little blood that they are virtually ineffective
What are the 2 treatment options for kidney failure?
1) Dialysis
-haemodialysis
-peritoneal dialysis
2) transplant
What does the term dialysis mean?
-the use of a partially permeable membrane to remove waste products (urea) and excess salts and water from the blood by the process of simple diffusion
Explain what haemodialysis is and how the process works
-the patient is attached to a dialysis machine, usually in a hospital, for about 8 hours, 2-3 times a week
-blood leaves an artery in the arm and flows into the machine (kept at 37 degrees). It flows in spaces between the partially permeable dialysis membranes. These membranes mimic the basement membrane (blood one one side, dialysis fluid on the other)
Explain why anti-coagulant is added to the blood when it leaves the body, and why it must be removed before the blood flows back into the body
-this prevents blood clots occurring while the blood is outside the body
-the blood needs to be able to clot when it returns to the body, because if they were to cut themselves it wouldn’t stop bleeding
Why must people having renal dialysis carefully control their diet in between dialysis sessions?
-they must eat very little protein to minimise the amount of urea made, so concentration stays low in the blood
Describe and explain the composition of the dialysis fluid
1) contains no urea = concentration is always higher in blood, so urea diffuses down concentration gradient out of the blood
2) normal glucose concentration = so that glucose does not diffuse out of the blood into the dialysis fluid as it is needed by the body
3) same normal mineral ions concentration as blood = any excess mineral ions can leave the blood by diffusion, so normal electrolyte/ osmotic balance of the blood is maintained
4) as excess ions and urea leave the blood, some water leaves by osmosis too, to prevent the build up of fluid in the body/ removes excess water
Why do the blood and dialysis fluid flow in opposite directions?
-to maintain a counter current exchange system, maximising the rate of diffusion of urea out of the blood into the dialysis fluid
-if they flowed the same way an equilibrium would occur and not all of the urea would leave the blood
Why might people who receive dialysis feel unwell in between sessions?
-urea starts to build up in the blood, which is toxic
-may have salt/ mineral ion imbalance, which has osmotic effects on cells
Explain what peritoneal dialysis is and how it’s carried out
-this type of dialysis occurs inside the body, using the peritoneum membrane, which forms the lining of the abdomen
-usually done at home and patient can carry on with their life fairly normally
-dialysis fluid is introduced into the abdomen using a catheter, and is left there for several hours, allowing dialysis to occur across the peritoneal membrane. Urea, excess mineral salts and water diffuse out of the surrounding blood capillaries into the tissue fluid, across the peritoneum, into the dialysis fluid. After several hours the dialysis fluid is drained off and discarded
