Kidney Failure

A set of revision cards on kidney failure, dialysis and kidney transplants.

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Kidney Failure

Can occur because:

  • diabetes mellitus (both type 1 and type 2 sugar diabetes)
  • hypertension
  • infection

Once kidneys fail body unable to remove excess water, urea and salts.

Unable to regulate levels of water and salts.

This can lead to death.

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Dialysis

  • Most common treatment
  • Removes wastes, excess fluid and salt from blood by passing over a dialysis membrane
  • Dialysis membrane is a partially permeable membrane
  • Allows exchange of substances between blood and dialysis fluid
  • Fluid contains correct concentrations of salts etc.
  • Excess substances can diffuse across membrane into dialysis fluid.
  • Too low concentrations causes substances to diffuse from dialysis fluid into blood
  • Must be combined with carefully monitored diet.
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Haemodialysis

  • Blood from a vein is passed into a machine containing artificial dialysis membrane
  • Heparin is added to avoid clotting 
  • Any bubbles are removed before blood returns to body
  • Usually performed at a clinic 3 times a week for several hours at each session
  • Some patients learn to carry it out at home.
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Peritoneal Dialysis (PD)

  • The filter is the body's own abdominal membrane (peritoneum)
  • A surgeon implants a permanent tube in abdomen
  • Dialysis solution is poured through tube and fills space between abdominal wall and organs
  • After several hours solution is drained from abdomen.
  • PD is usually performed in several consecutive sessions daily
  • At home or work
  • The patient can walk around while having dialysis
  • Ambulatory PD
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Kidney Transplant

  • Old kidneys left in place unless likely to cause infection or are cancerous
  • Donor kidney can be from a living relative or from someone who has died
  • Major Surgery
  • While patient is under anaesthesia, surgeon implants nerw organ into lower abdomen
  • Then attaches it to blood supply and bladder
  • Many patients feel much better immediately after transplant
  • Best life extending treatment for kidney failure
  • Patient's immune system will regonise new organ as foreign object
  • Patients must be given immunosuppressant drugs to prevent rejection
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Advantages of kidney transplant

  • Freedom from time consuming dialysis
  • Diet is less limited
  • Feel better physically
  • Better quality of life - able to travel etc.
  • No longer see self as chronically ill
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Disadvantages of kidney transplant

  • Need immunosuppressants for life of kidney
  • Need major surgery under general anaesthetic
  • Risks of surgery - infection, bleeding, damage to surrounding organs
  • Frequent checks for signs of organ rejection
  • Side effects - antirejection medicines cause fluid retention and high blood pressure. Immunosuppressants increase susceptibilty to infections
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Testing urine samples

  • Substances with Mr of 69000 or less can enter nephron
  • And metabolic product or substance in blood can pass into urine, as long as it is small enough
  • If these substances are not reabsorbed they can be detected in urine.
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Pregnancy Testing

  • Once implanted in uterine lining, embryo secretes hormone human chorionic gonadotrophin (hCG)
  • hCG is a small glycoprotein with Mr of 36700
  • Can be found in urine as early as 6 days after conception
  • Pregnancy tests are manufactured with monoclonal antibodies
  • Only binds to hCG, no other hormones
  • When woman takes pregnancy test she soaks portion of strip in urine
  • Any hCG attaches to an anitbody that is attached with a blue bead
  • hCG anitbody complex moves up strip until sticks to band of immobilised antibodies
  • As a result all anitbodies carring a blue bead and attached to hCG are held in place forming a blue line
  • There is always a control blue line for comparison, second line indicates pregnancy
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Testing for anabolic steroids

  • Anabolic steroids increase protein synthesis within cells
  • This results in build up of cell tissue, especially in muscles
  • Non medical uses are controversial as can give advantage in competitive sports and have dangerous side effects
  • Use of anabolic steroids is banned by all major sporting bodies
  • Have a half life of about 16 hours and remain in blood for many days
  • Relatively small molecules and enter nephron easily
  • Testing involves analysing a urine sample in a lab using gas chromatography or mass spectrometry
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Gas Chromatography

  • The sample is vaporised in the presense of a gaseous solvent
  • Passed down a long tube lined by an absorption agent
  • Each substance dissolves differently in the gas and stays there for a unique specific retention time
  • Eventually the substance comes out of the gas and is absorbed onto the lining.
  • Then analysed to produce a chromotogram
  • Standard samples of drugs, as well as urine samples are run so that drugs can be identified and quanitfied in the chromotograms.
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