5.2.8

• Assessing Kidney function

  can be assessed by estimating the glomerular filtration rate (GFR) and by analysing the urine for substances such as proteins

  • protein in the urine indicates flitration mechanism has been damaged
  • GFR is a measure of how much fluid passes into the nephrons each minute
  • normal reading is in range 90-120 cm3/min

  → figure below 60 is an indication of chronic kidney disease
• Causes of kidney failure

  include diabetes mellitus (both Type 1 + 2 ), heart disease, hypertension and infection
• Treatment of kidney failure

  Renal Dialysis

  • most common treatment for kidney failure
  • waste products, excess fluid and mineral ions are removed from the blood by passing it over a partially membrane dialysis membrane that allows the exchange of substances between the blood and dialysis fluid
  • dialysis fluid contains correct concentrations of mineral ions, urea, water and other substances found in blood plasma

  → any substance in excess in blood diffuse across the membrane into dialysis fluid ; any substance too low in concentration diffuse into blood from dialysis fluid
• two types of renal dialysis :

  Haemodialysis + Peritoneal Dialysis (PD)
• Haemodialysis

  blood from an artery vein is passed into a machine that contains an artificial dialysis membrane shaped to form many artificial capillaries, which increases the surface area for exchange

  • heparin is added to avoid clotting
  • the capillaries are surrounded by dialysis fluid, which flows in the opposite direction of the blood (countercurrent flow)

  → this improves the efficiency of exchange and any bubbles before the blood is returned to the body via a vein
• Peritoneal Dialysis (PD)

  the dialysis membrane is the body’s own abdominal membrane (peritoneum)

  • a surgeon has to first implant a permanent tube in abdomen

  → dialysis solution is poured through the tube + fills the space between abdominal wall and organs

  → after several hours, the used solution is drained from abdomen

  • PD can be carried out at home or work as patient can walk around while having dialysis , method is sometimes called ambulatory PD
• Kidney Transplant

  best life extending treatment as it involves a major surgery

  • while patient is under anaesthesia, the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply + bladder
  • patients are given immunosuppressant drugs to help prevent their immune system recognising the new organ as a foreign object + rejecting it
• Kidney Transplant

  disadvantages

  • need to take immunosuppressant drugs
  • need for major surgery under general anaesthesia
  • need for regular checks for signs of rejection
  • side effects of immunosuppressant drugs - fluid retention, high blood pressure, susceptibility to infections
• Urine Analysis

  molecules with a relative molecular mass of less than 69000 can enter the nephron and if these substances are not reabsorbed further down the nephron they can be detected in urine

  e.g. urine can be tested for

  • glucose in diagnosis of diabetes
  • alcohol to determine blood alcohol levels ind drivers
  • many recreational drugs
  • human chorionic gonadotrophin (hCG) in pregnancy testing
  • anabolic steroids, to detect improper use in sporting competitions
• Pregnancy Testing

  Pregnancy testing when a human embryo is implanted in uterine lining, they produce a hormone called human chorionic gonadotrophin (hCG) which is a relatively small molecule of 36700 molecular mass , that can be found as early as 6 days after conception
• Testing for anabolic steroids

  anabolic steroids increase protein synthesis within cells, resulting in build-up of cell tissue especially in muscles

  • non medical uses for them are controversial as they have many advantages and dangerous side effects in sport
  • they have a half-life of about 16 hours and remain in blood for many days

  → they are relatively small molecules which can therefore enter nephron

  • testing for anabolic steroids involves analysing a urine sample in a laboratory using gas chromatography