Clinical Chemistry CPC

Question 1

Which of the following commonly presents with depression?

A. Hyperkalaemia

B. Hypokalaemia

C. Hypercalcaemia

D. Hypocalcaemia

E. Uraemia

Answer 1

c. Hypercalcaemia

Abdominal moans, psychic groans..

Question 2

What is the X-ray diagnosis?

A.Normal

B.Colles fracture

C.Pott’s fracture

D.Osteoporosis

E.Osteomalacia

F.Smith’s fracture

Answer 2

F. Smith’s fracture

A Smith’s fracture, also sometimes known as a reverse Colles’ fracture or Goyrand-Smith’s, is a fracture of the distal radius. It is caused by a direct blow to the dorsal forearm or falling onto flexed wrists, as opposed to a Colles’ fracture which occurs as a result of falling onto wrists in extension.

Question 3

What does this X-ray show (Reverse of Smith’s)?

Answer 3

Colles’ fracture

A Colles Fracture is a complete fracture of the radius bone of the forearm close to the wrist resulting in an upward (posterior) displacement of the radius and obvious deformity.

Question 4

What is a Pott’s fracture?

Answer 4

• Ankle fracture
• Involved tibia and fibula

Pott’s fracture, also known as Pott’s syndrome I and Dupuytren fracture, is an archaic term loosely applied to a variety of bimalleolar ankle fractures. The injury is caused by a combined abduction external rotation from an eversion force.

Question 5

What does this show?

A.Ketonuria

B.Glycosuria

C.Haematuria (large)

D.Non-haemolysed trace of blood

E.Proteinuria

Answer 5

C. Haematuria (large)

Question 6

52 year old with depression, on St John’s wort, has come into A&E with severe abdominal pain. Urine dipstick shows haematuria (large).

What is the likely cause?

A.DKA

B.Glomerulonephritis

C.Acute rheumatic fever

D.Subacute bacterial endocarditis

E.Renal stones

Answer 6

E. renal stones

**Nephritis is painless – can have poor urine output, or just normal urine output but poor quality urine

Microhaematuria + fever = think endocarditis

Question 7

52 year old with depression, on St John’s wort, has come into A&E with severe abdominal pain. Urine dipstick shows haematuria (large), has suspected renal stones.

What is the best investiagtion?

A.arterial blood gases

B.renal biopsy

C.plain abdominal X-ray

D.abdominal ultrasound

E.echocardiogram

Answer 7

C. Plain abdominal X-ray

*Ultrasound picks up non-calcified stones which are rarer

Question 8

What does this investigation show? (plain abdo X-ray)

A.Glomerulonephritis

B.Renal stones

C.Diabetic ketoacidosis

D.Aortic aneurysm

E.Pott’s disease

F.Gallstones

Answer 8

B. renal stones

Question 9

52 year old with depression, on St John’s wort, has come into A&E with severe abdominal pain. Urine dipstick shows haematuria (large), plain abdominal X ray shows multiple renal stones.

What test do you want to do next?

A. Arterial blood gases

B. Fasting glucose

C. Plasma calcium

D. Plasma PTH

E. Plasma vitamin D

Answer 9

c. Plasma calcium

You must have a Ca to interpret a PTH

Question 10

52 year old with depression, on St John’s wort, has come into A&E with severe abdominal pain. Urine dipstick shows haematuria (large), plain abdominal X ray shows multiple renal stones.

Ca is 2.82 NR(2.2-2.6)

1. What are you’re 3 differential diagnoses?
2. What single investigation will distinguish between the 3?

Answer 10

• Cancer
• Primary hyperparathyroidism
• Sarcoidosis

Question 11

52 year old with depression, on St John’s wort, has come into A&E with severe abdominal pain. Urine dipstick shows haematuria (large), plain abdominal X ray shows multiple renal stones.

Ca is 2.82 NR(2.2-2.6)

Top 3 differentials: cancer, primary hyperparathyroidism and sarcoidosis.

What single investigation will distinguish between these potential diagnoses?

A.PTH

B.Vit D

C.Bone scan

D.CXR

E.CT thorax

Answer 11

A. PTH

Question 12

52 year old with depression, on St John’s wort, has come into A&E with severe abdominal pain. Urine dipstick shows haematuria (large), plain abdominal X ray shows multiple renal stones.

Ca is 2.82 NR(2.2-2.6) and PTH is 3 (1.1-6.8pM)

Which of the following is the likely cause?

1. Cancer
2. Primary hyperparathyroidism
3. Sarcoidosis

Answer 12

2. Primary hyperparathyroidism

With high calcium, the PTH should be suppressed completely, even if the normal reference range. If PTH is not suppressed by high Ca then it is inappropriate

Question 13

What is PTH related peptide, and its relation to cancer?

Answer 13

PTH related peptide – if cancer expresses this gene, there is a 6 month survival. The gene is necessary in fetal development in order to take calcium from the mother for normal skeletal growth. Continues in breast feeding, where PTHrP is produced to release calcium to make breast milk

PTHrP expressed in cancer allows for tumor cells to invade bone, causing Ca loss

Question 14

Describe why hypercalcaemia occurs in hyperparathyroidism

Answer 14

Hyperparathyroidism e.g. Parathyroid adenoma

Causes uncontrolled release of PTH

PTH actions:

• Efflux of calcium from bone
• Decreased loss of Ca in urine
• PTH activates 1 alpha hydroxylase in the kidney, this activates the active form of Vitamin D which aids absorption of Ca in the intestine

All in all, increases concentration of calcium in blood

Question 15

Describe basic vitamin D metabolism

Answer 15

• UV absorbed by the skin producing 7-dehydrocholesterol in the skin
• This is then converted to cholecalciferol (D3) in the gut
• Cholecalciferol is converted to 25-OH-D3 by the liver
• 25-OH-D3 is converted by 1alpha OHdase (activated by PTH) which is released from the kidney to 1,25-(OH)2-D3. This is the active form of Vitamin D

Question 16

Define primary hyperparathyroidism

Answer 16

Raised/inappropriate “normal” PTH in the presence of hypercalcaemia

Question 17

What are the

1. Symptoms
2. Signs
3. Complications

Of hypercalcaemia?

Answer 17

1. Symptoms

• Moans/Bones/Groans/Stones
• Asymptomatic
• Polydypsia/Polyuria (Nephrogenic DI)

2. Signs
   * Band keratopathy - calcium deposition on the front of the eye
3. Complications

• Renal stones
• Pancreatitis
• Peptic ulcer disease
• Skeletal changes

Question 18

What are the most common renal stones?

Answer 18

• Calcium oxalate monohydrate - 40-60%
• Calcium oxalate dehydrate - 40-60%
• Calcium phosphate - 20-60%
• Mixed calcium oxalate-phosphate - 35-40%

Question 19

Are the following stones radio-opaque or radiolucent:

1. Calcium oxalate monohydrate
2. Uric acid

Answer 19

1. Radio-opaque
2. Radiolucent

Question 20

Describe the following about renal calcium stones

1. Risk factors
2. Presentation
3. Investigations
4. Natural history
5. Treatment
6. Prevention

Answer 20

1. RFs:

• FH
• Dehydration
• hypercalciuria (>6mmol Ca/day)
• hypercalcaemia
• HPTH

2. Presentation:

• Pain (colic)
• haematuria
• recurrent infection
• renal failure

3. Ix:

• KUB
• stone analysis
• urine
• serum biochemistry

4. Natural Hx: Most stones pass
5. Treatment:

• Lithotrypsy
• cystoscopy
• lithotomy

6. Prevention:

• Drink more water
• treat hypercalciuria (eg thiazides) &/or hypercalcaemia as necessary.

Question 21

What can proteus mirabilis cause?

Answer 21

Proteus mirabilis is a Gram-negative, facultatively anaerobic, rod-shaped bacterium. It shows swarming motility and urease activity. P. mirabilis causes 90% of all Proteus infections in humans.

Cause recurrent UTIs

Question 22

What is the emergency management of hypercalcaemia?

Answer 22

•Ca2+ >3.0 mmol/L &/or unwell

• (Dehydrated, confused, drowsy, coma, seizures, renal failure)
• Saline and furesomide - 1L over an hour to begin with as dehydrated. Saline is safe in most conditions, except in liver failure when they reabsorb too much Na.
• High calcium causes osmotic diuresis
• IV access (venflon/central line)
• Catheter
• Rehydrate: 0.9% saline (can be litres++)
• Initiate calciuresis:

0.9% saline

Frusemide

•IV pamidronate 30 - 60 mg (hold off)

Question 23

What are non-emergency managements for hypercalcaemia?

Answer 23

• Keep well hydrated
• Avoid thiazides
• Surgery - e.g. removal of parathyroid adenoma - minimally invasive parathyroidectomy

Question 24

What are the classical signs of primary hyperparathyroidism?

Answer 24

• Bones (fractured)
• Stones (renal)
• Moans (depression)
• Groans (abdo pain, pancreatitis)

Question 25

A patient has a high calcium (2.85) and a normal PTH. What will the bone findings show on an X-ray of the hand?

A.Normal

B.Looser’s zones

C.Ulnar aspect cystic changes

D.Radial aspect cystic changes

E.Changes in random carpal bones

Answer 25

Patient has hyperparathyroidism

D. Radial aspect cystic changes

Question 26

A patient has a high calcium (2.85) and a normal PT, so primary hyperparathyroidism. Bone findings show of an X-ray of the hand showed Radial aspect cystic changes.

What will the histology of the bone show?

A.Normal

B.Brown tumours

C.Multinucleate giant cells

D.No idea

Answer 26

B. Brown tumours and C. multinucleate giant cells

Question 27

45 year old Afrocaribean man presents with dyspnoea.

Which is the most helpful investigation ?

A.Full blood count

B.Urea and electrolytes

C.Chest X-ray

D.ECG

E.echocardiogram

Answer 27

C. chest X-ray

Then FBC

Question 28

45 year old Afrocaribean man presents with dyspnoea. He has a chest X-ray

What does this image show?

Answer 28

Bilateral hilar lymphadenopathy

Question 29

45 year old Afrocaribean man presents with dyspnoea. Chest X-ray shows bilateral hilar lymphadenopathy. Ca is 2.82

What should the PTH to be?

Answer 29

PTH suppressed to undetectable levels

Question 30

45 year old Afrocaribean man presents with dyspnoea. Chest X-ray shows bilateral hilar lymphadenopathy. Ca is 2.82, PTH is undetectable.

1. What is the likely diagnosis?
2. Why does it cause hypercalcaemia?
3. When does this condition get worse?

Answer 30

1. Sarcoidosis
2. Systemic didease where macrophages express 1 alpha hydroxylase

• 1 alpha hydroxylase is needed to create the active form of vitamin D, therefore lots of vitamin D is activated, and increases the absorption of Ca from the gut.
  3. More common/worse in summer months due to the increase in sunlight - increased vitamin D.