Kidney failure and medical diagnosis

Question 1

Describe ways in which the kidneys can be damaged.

Answer 1

1. Kidney infections- where the structure of podocytes and tubules may become damaged and destroyed
2. Raised blood pressure- damage the structure of epithelial cells and basement membrane of the Bowman’s capsule
3. Genetic conditions- e.g polycystic kidney disease where the healthy kidney tissue is replaced by fluid-filled cysts or damaged by pressure from cysts.

Question 2

Describe how the components of urine may be affected by if the kidneys are infected or affected by high blood pressure

Answer 2

1. Proteins in the urine- if the basement membranes or podocytes of the Bowman’s capsule are damaged, they are no longer acts as filters and large plasma proteins can pass into the filtrate and are passed out in the urine
2. Blood in the urine- another symptom that the filtering process is no longer working.

Question 3

Describe 6 effects of kidney failure.

Answer 3

1. Loss of electrolyte balance- if the kidney’s fail, the body cannot excrete sodium, potassium and chloride ions. This causes osmotic imbalances in the tissues and eventual death
2. Build-up of toxic urea in the blood- if the kidneys fail, the body cannot get rid of urea and it can poison the cells.
3. High blood pressure- the kidneys play an important role in controlling the blood pressure by maintaining the water balance of the blood. If the kidneys fail, the blood pressure increases and this can cause a range of health problems and strokes.
4. Weakened bones- calcium/ phosphorus balance in the blood is lost
5. Pain and stiffness in joints as abnormal proteins build up in the blood
6. Anaemia- the kidneys are involved in the production of a hormone called erythropoietin that stimulates the formation of red blood cells . When the kidneys fail it can reduce the production of red blood cells causing tiredness and lethargy

Question 4

State one measure that is used to indicate kidney disease.

Answer 4

1. Measuring glomerular filtration rate

Question 5

Describe how glomerular filtration rate can be estimated and describe the precautions that need to be taken when interpreting the results.

Answer 5

1. The rate of filtration is not measured directly
2. A blood test measure the levels of creatinine in the blood- creatinine is a breakdown product of muscles and gives an estimate eGFR
3. The units cm^3/min
4. If the levels of creatinine in the blood go up, it is a signal that the kidneys are not working properly,
5. Factors need to be taken into account e.g GFR decreases with age and men normally have more muscle mass and so creatinine than women

Question 6

State the two main ways in which kidney failure is treated.

Answer 6

1. Dialysis

2. Transplant

Question 7

Define renal dialysis

Answer 7

1. A process where the function of the kidney are carried out artificially to maintain the salt and water balance of the blood

Question 8

Define heamodialysis

Answer 8

1. The filtering of blood through a semi-permeable membrane in the dialysis machine to remove waste products.

Question 9

Define peritoneal dialysis

Answer 9

1. A type of dialysis that uses the peritoneum in a person’s abdomen as the membrane through which fluid and dissolved substances are exchanged with the blood.

Question 10

Describe the process of heamodialysis

Answer 10

1. Usually carried out in hospital
2. Blood leaves the patient’s body from an artery and flows into the dialysis machine where it flows between partially permeable dialysis membranes
3. These membranes mimic the basement membrane of the Bowman’s capsule. On the other side of the membranes is the dialysis fluid.
4. During dialysis it is vital that patients lose the excess urea and mineral ions that have built up in the blood
5. It is equally important that they do not lose useful substances such as glucose and some mineral ions

Question 11

What is the countercurrent exchange system in heamodialysis

Answer 11

1. The blood and the dialysis fluid flow in opposite directions to maintain a countercurrent exchange system,
2. This maximises the exchange that takes place

Question 12

What are the implications of haemodialysis for the patient

Answer 12

1. It takes about 8 hours and has to be repeated regularly
2. Have to remain attached to a machine several times a week for many hours
3. They also need to manage their diets carefully. eating relatively little protein and salt and monitoring their fluid intake to keep their blood chemistry
4. Takes place in hospital generally

Question 13

Describe the constituents of the dialysis fluid and explain why this make up is necessary.

Answer 13

1 . The dialysis fluid controls the loss of these substances- it contains normal blood plasma levels of glucose to ensure there is no net movement of glucose out of the blood.

2. The dialysis fluid also contains normal plasma levels of mineral ions so any excess mineral ions in the blood move out by diffusion down a concentration gradient into the dialysis fluid, thus restoring the correct electrolyte balance of the blood
3. The dialysis fluid contains no urea meaning there is a very steep concentration gradient from the blood to the fluid and as a result much of the urea leaves the blood

Question 14

Describe how molecules move across the dialysis membrane.

Answer 14

1. Diffusion down a concentration gradient

2. No active transport

Question 15

Describe the process of peritoneal dialysis.

Answer 15

1. Is done inside the body- it makes use of the natural dialysis membranes formed by the lining of the abdomen- the peritoneum
2. It is usually done at home and the patient can carry on with their normal life while it takes place
3. The dialysis fluid is introduced into the abdomen using a catheter.
4. It is left for several hours dialysis to take place across the peritoneal membranes, so that urea and excess mineral ions pass out of the blood capillaries, into the tissue fluid and out across the peritoneal membrane into the dialysis fluid
5. The fluid is then drained off and discarded, leaving the blood balanced again and the urea and excess minerals removed

Question 16

Describe how transplantation can treat kidney failure

Answer 16

1. The blood vessels are joined and the ureter of the new kidney is inserted into the bladder
2. If transplant successful, the kidney will function for many years

Question 17

Describe the limitations of transplantation as a treatment for kidney failure.

Answer 17

1. The main problem with transplanted organs is the risk of rejection. The antigens on the donor organ differ from the antigens on the cells of the recipient and the immune system is likely to recognise this.
2. Transplanted organs don’t last forever with the average transplanted kidney functioning for around 9-10 years, although some last longer.

Question 18

What measures can be taken to reduce the risk of kidney rejection

Answer 18

1. The match between the antigens of the donor and the recipient is made as close as possible
2. Recipient is given immunosuppresent drugs for the rest of their lives.
3. But immunosuppresent drugs is that they prevent the patients from responding effectively to infectious diseases

Question 19

Draw a table to compare treating kidney failure with dialysis and treating kidney failure with transplantation

Answer 19

1. Dialysis is more readily available than donor organs
2. Dialysis enables the patient to lead a relatively normal life
3. However dialysis patients have to monitor their diet carefully and need regular sessions on the machine.
4. Long-term dialysis is much more expensive than a transplant and can eventually cause damage to the body
5. Kidney transplant patients are free from the restrictions which come with regular dialysis sessions and dietary monitoring

Question 20

Explain, in general, why analysis of urine can act as a good diagnostic test for different diseases

Answer 20

1. Urine contains the breakdown products of a whole range of chemicals, including hormones and any toxins taken into the body
2. If you are affected by one of a number of different diseases, new substances will show up in your urine
3. The presence of glucose in the urine is a well-known symptom of type 1 and type 2 diabetes,
4. If you have muscle damage large amounts of creatinine will show up in your urine.

Question 21

Name the hormone tested for in pregnancy tests and state where it is produced and when it starts being produced.

Answer 21

1. The human embryo implants in the uterus, around 6 days after conception
2. The site of the developing placenta then begins to produce a chemical called human chorionic gonadotrophin (hCG). Some of this hormone is found in the blood and the urine of the mother.
3. Modern pregnancy tests still test for hCG in the urine, but they rely on monoclonal antibodies. Some are so sensitive that pregnancy can be detected within hours of implantation.

Question 22

Define the term “monoclonal antibody”

Answer 22

1. Monoclonal antibodies are antibodies from a single clone of cells that are produced to target particular cells or chemicals in the body

Question 23

Describe how monoclonal antibodies to hCG are produced.

Answer 23

1. A mouse is injected with hCG so it makes the appropriate antibody
2. The b-cells that make the required antibody are then removed from the spleen of the mouse and fused with a myeloma, a type of cancer cell which divides very rapidly.
3. This new fused cell is known as a hybridoma.
4. Each hybridoma reproduces rapidly resulting in a clone of millions of ‘living factories’ making the desired antibody.
5. These monoclonal antibodies are collected, purified and used in a variety of ways.

Question 24

Describe the main stages in a pregnancy

Answer 24

1. The wick is soaked in the first urine passed in the morning- have highest levels of hCG
2. The test contains monoclonal antibodies that have very small coloured beads attached to them. They will only bind to hCG. If the woman is pregnant the hCG in her urine binds to the mobile monoclonal antibodies and forms a hCG/antibody complex
3. The urine caries on along the test structure until it reaches a window
4. Here there are immobilised monoclonal antibodies arranged in a line or a pattern such as a positive sign that only bind to the hCG/antibody complex.- a coloured pattern appears in the first window.
5. The urine continues up through the test to a second window
6. Here there is usually a line of immobilised monoclonal antibodies that bind only to the mobile antibodies, regardless of whether they are bound to hCG or not. This coloured line forms regardless of whether the woman is pregnant- indicated the test is working.

Question 25

Define the term “anabolic steroid” and explain why they may give a benefit to athletes.

Answer 25

1. Anabolic steroid- drugs that mimic the action of the male sex hormone testosterone and they stimulate the growth of muscles.

Question 26

Describe how urine is tested for anabolic steroids.

Answer 26

1. They are excreted in the urine
2. By testing the urine using gas chromatography and mass spectrometry, scientists can show that an individual has been using these drugs which are banned in all sports.
3. The urine sample is vapourised with a known solvent and passes along a tube.
4. The lining of the tube absorbs the gases and is analysed to give a chromatogram that can be read to show the presence of the drugs.

Question 27

Describe how urine testing is used to see if someone has been taking illegal drugs.

Answer 27

1. Urine is tested for the presence of many different drugs including alcohol.
2. If someone is suspected of having taken an illegal drug, they may be asked to provide a urine sample and this will be divided into two.
3. The first sample may be tested by an immunoassay using monoclonal antibodies to bind to the drug or its breakdown product.
4. If positive, then the second sample may be run through a gas chromatograph/mass spectrometer to confirm the presence of the drug.

Question 28

Explain why it may be possible to test for drug use some time after a person has taken the drug.

Answer 28

1. Because drugs or metabolites (which are the breakdown products of drugs)- are filtered through the kidney and stored in the bladder, it is possible to find drug traces in the urine some time after the drug has been used