Biochemistry results

Question 1

What test can be done to determine if hyponatraemia is a true finding?
And what will the result be if it is a true hyponatraemia?

Answer 1

Serum osmolality

It will be low

Question 2

After determining a true hyponatraemia, what is the next assessment?

Answer 2

Determining the patients volume status, eg dehydrated (hypovolaemic), fluid overloaded (hypervolaemic) or normally hydrated (isovolaemic)

Question 3

What are common causes of hypovolaemic hyponatraemia?

Answer 3

Extra-renal causes: GI-vomiting or diarrhoea

Renal causes: diuretics, salt-wasting renal disease, nephropathy, adrenal insufficiency

Question 4

What are the common causes of isovolaemic hyponatraemia?

Answer 4

Water intoxication (urine osmolality 100mosmol)
Drugs
Renal failure
Hyperthyroidism

Question 5

What are the common causes of hypervolaemic hyponatraemia?

Answer 5

Liver failure
Congestive cardiac failure
Renal failure
Nephrotic syndrome

Question 6

What are causes of hypernatraemia?

Answer 6

Diabetes insipidus
Poor water intake
Administration of excess sodium in IV fluids
Administration of drugs containing high concn of Na

Question 7

What are common causes of hypokalaemia?

Answer 7

Drugs: diuretic therapy
Intestinal losses: excess vomiting, profuse diarrhoea, high stoma or fistula output
Renal tubular disease: renal tubular acidosis
Endocrine causes
Metabolic alkalosis

Question 8

What are common causes of hyperkalaemia?

Answer 8

Renal failure
Drugs: excess potassium supplementation, potassium-sparing diuretics, 
Rhabdomyolysis
Endocrine disease (hypoadrenalism)
DKA
Haemolysis of blood sample

Question 9

At what levels does hyperkalaemia need immediate attention?

Answer 9

> 6.5mmol/l or between 4.5-6.5mmol/l with ECG changes

Question 10

What is considered to be a normal GFR?

Answer 10

Approx 100ml/min per 1.73m(2)

Question 11

What is measured in a nutritional profile?

Answer 11

Magnesium
Calcium
Phosphate
Albumin

Question 12

What are the common causes of a poor nutritional profile?

Answer 12

Poor oral diet (eg alcoholic, hunger strike)

Malabsorption

Question 13

What happens to the biochemistry in re-feeding syndrome?

Answer 13

Dangerous shifts in electrolytes (eg magnesium, phosphate, calcium)

Question 14

What would the urinary sodium result be in a prerenal uraemia?

Answer 14

Low urinary sodium

Question 15

What would the urinary sodium result be in an acute tubular necrosis?

Answer 15

High urinary sodium

Question 16

What are the components of a bone profile?

Answer 16

Calcium
Phosphate
Alkaline phosphatase
Albumin

Question 17

What would the results of a bone profile be in osteoporosis?

Answer 17

All normal

Question 18

What would bone profile show in Paget’s disease?

Answer 18

Normal calcium and phosphate

Increased ALP

Question 19

What would bone profile show in primary hyperparathyroidism?

Answer 19

Increased calcium
Decreased phosphate
Increased ALP

Question 20

What would bone profile show in osteomalacia?

Answer 20

Normal/decreased calcium
Decreased phosphate
Increased ALP

Question 21

What would a bone profile show in the presence of bony metastases?

Answer 21

Increased/normal calcium
Normal/increased phosphate
Increased ALP

Question 22

What are causes of hypercalcaemia?

Answer 22

Bony mets
Multiple myeloma
Hyperparathyroidism
Excess vitamin D intake

Question 23

What are the three classifications of deranged LFTs?

Answer 23

Hepatitic
Cholestatic
Mixed

Question 24

Which LFTs will be abnormal in a hepatitic pattern?

Answer 24

Raised AST

Raised ALT

Question 25

Which LFTs will be abnormal in a cholestatic pattern?

Answer 25

Raised ALP | Raised GGT

Question 26

What are the causes of a hepatitic pattern of LFTs?

Answer 26

``` Viral hepatitis Autoimmune hepatitis Drugs/toxins Alcohol Metabolic disorders (eg Wilson's disease) Fatty liver Malignancy CCF ```

Question 27

What are the causes of a cholestatic pattern of LFTs?

Answer 27

Bile duct obstruction: gallstone Abnormal bile duct wall: bile duct stricture, cholangiocarcinoma Compression of bile duct by external lesion: pancreatic carcinoma, nodes of porta hepatis, ampullary carcinoma

Question 28

What are the causes of a raised ESR with a normal CRP?

Answer 28

SLE | Multiple myeloma

Question 29

What can cause hyperuricaemia?

Answer 29

Increased purine consumption or uric acid production | Impaired excretion of uric acid

Question 30

What tumours are associated with raised alpha-fetoprotein?

Answer 30

Hepatocellular carcinoma | Testicular carcinoma

Question 31

The sweat test is used to detect CF. What are common causes of a false-positive sweat test?

Answer 31

Adrenal insufficiency Anorexia nervosa Coeliac disease Hypothyroidism

Question 32

What test will represent how well the liver is functioning?

Answer 32

Prothrombin time