CHEMPATH: EMQs on enzymes and chemistry

Question 1

Which one is increased in a patient with Paget’s disease of the bone?

Answer 1

C - alkaline phosphatase (ALP) and osteocalcin

Increased due to increased activity of both osteoblasts (causes raised osteocalcin) and osteoclasts

Question 2

List 3 features of Paget’s disease.

Answer 2

• Asymptomatic
• Bowed tibia (it will also be warm)
• High risk of fracture

Question 3

Which one is increased in a patient with osteomalacia?

Answer 3

PTH

Lack of vitamin D –> 2^nd HPT –> high PTH

Question 4

Which one is increased in a patient following an acute myocardial infarction?

Answer 4

Answer: troponins, CK (MB), AST, LDH

(AST is important in gluconeogenesis)

Question 5

What is raised in Addison’s disease?

Answer 5

potassium

Question 6

What is most raised in jaundice caused by a gallstone?

Answer 6

ALP - consider liver zonation

Question 7

Which one is most increased in a patient with jaundice caused by viral hepatitis?

Answer 7

ALT

Question 8

Which one is most increased in a patient with jaundice caused by chronic alcoholic cirrhosis?

Answer 8

AST

Question 9

Which one is most increased in a patient with prostatic carcinoma?

Answer 9

Acid phosphatase

Question 10

Which scan would you use to look for bony mets?

Answer 10

Bone scan Tc bisphosphonate

Question 11

What investigations are useful to make the diagnosis of Paget’s disease?

Answer 11

Bone scan with Tc bisphosphonate - used to see bone turnover in cancer patients to look for bony metastases

Question 12

Name another technetium 99 scan.

Answer 12

Technetium 99m (pertechnetate) scan for iodine uptake by thyroids:

• Diffuse uptake = diffuse goitre / Graves’ disease
• Unilateral uptake / hot nodule = adenoma

Tc99m-sestamibi for parathyroids - absorbed faster by a hyperfunctioning parathyroid gland than by a normal parathyroid gland

Question 13

What nuclear scan is used to look for abdominal metastases in oncology? What marker is used?

Answer 13

FDG-PET Scans – looks at glucose uptake​

Marker = FDG (fluorodeoxyglucose)

• Non-specific marker as glucose is taken up by ANY active cell
• Cancer cells are more active so they will take up more FDG

Question 14

What feature of a scan will indicate that you are looking at a Gallium 68 DOTATATE scan using somatostatin analogues?

Answer 14

Spleen will appear hot - because it has a lot of somatostatin receptors.

• Kidneys, pancreas, cysts in kidneys, and adrenals will also appear hot.
• Gallium 68 stuck onto a somatostatin analogue will go to tissues that have smatostatin receptors i.e. any neuroendocrine cells.

Question 15

Which scan would you use to visualise primary neuroendocrine tumours?

Answer 15

Neuroendocrine tumours (insulinomas)

Question 16

Which radionucleotide scan would you use to identify phaechromocytomas?

Answer 16

MIBG (Meta-Iodobenzylguanidine) Scan

+ Gallium dotatate - picks up any neuroendocrine tumour (includes phaeochromocytoma and insulinomas)

Question 17

Which radionucleotide scan can you use to look at the parathyroids?

Answer 17

Sestamibi / Sesta MIBI (scintigraphy)

• Tc99m-sestamibi is absorbed faster by a hyperfunctioning parathyroid gland than by a normal parathyroid gland

Question 18

How would the myocardium appear on Sestamibi scan during MI?

Answer 18

There would be an area of lack of uptake

Question 20

Label these parts of the portal triad.

Answer 20

Question 21

Which liver zone is damaged in obstructive jaundice causing a rise in ALP?

Answer 21

Zone 1 - around the bile duct in the portal triad

Question 22

What is raised in someone with primary HPT?

Answer 22

Calcium

Question 23

What is low in primary HPT?

Answer 23

vitamin D

Question 24

What rises the most in acute renal failure?

Answer 24

Urea - if caused by dehydration

Question 25

What rises the most in chronic renal failure?

Answer 25

creatinine - because there is a fall in GFR

Question 26

What is a marker of glucose control over last 3 months?

Answer 26

HbA1c

Question 27

What is a marker of glucose control over last 3 weeks?

Answer 27

fructosamine

Used in pregnancy where you cannot wait 3 months to assess HbA1c. Glucose control becomes very important later in pregnancy as more insulin resistance may develop.

Question 28

When will AST rise after MI and how long will it remain elevated?

Answer 28

• Goes up ~3 days after an MI
• Remains for around 14 days (3-14 days)

Enzymes that increase following MI:

• Troponins (B, D)
• CK MB (C)
• Myoglobin (A)
• AST
• LDH

Question 29

Why does rhabdomyolysis cause acute kidney injury?

Answer 29

Myoglobin is very nephrotoxic

Very high CK (from muscle breakdown) will lead to renal failure

Question 30

How can you prevent renal failure after rhabdomyolysis?

Answer 30

IV bicarbonate - allows excretion of extra CK

Question 31

What is the ratio of AST to ALT in differrent conditions?

Answer 31

ALT> AST - in patients with viral hepatitis

AST to ALT of 2:1 - in patients with chronic alcoholic cirrhosis

Question 32

What are the main 5 indications for dialysis?

Answer 32

• Indications for Dialysis:
  
  • Refractory hyperkalaemia
  • Refractory fluid overload
  • Metabolic acidosis
  • Uraemic symptoms (encephalopathy, nausea, pruritis, malaise, pericarditis)
  • CKD stage 5 (GFR <15mL/min)