Clinical Chemistry CPC

Question 1

What are the effects of calcium derangement on the brain and CNS?

Answer 1

HYPO: neuromuscular irritability, anxiety, numbness, tetany
HYPER: Depression + tiredness

Question 2

What are the effects of potassium derangement on the heart?

Answer 2

HYPO increases myocardial excitability: arrhythmia- VF, VT, TDP
HYPER decreases myocardial excitability: bradyarrythmia, asystole

Question 3

What is a Smiths Fracture? What is it caused by?

Answer 3

POSTERIOR displacement of the RADIUS
Falling on flexed wrist pushes Radius towards back of hand

Question 4

What is a Colle’s Fracture? What is it caused by?

Answer 4

ANTERIOR displacement of the RADIUS
Falling on extended wrist pushes radius towards palm of hand

Question 5

What is a Pott’s fracture?

Answer 5

Ankle fracture involving TIBIA + FIBULA

Question 6

What would urine dipstick show in renal stones?

Answer 6

MACROscopic haematuria (tear urothelium)
(+ abdo pain)

Question 7

What would urine dipstick show in glomerulonephritis?

Answer 7

MICROscopic haematuria (not overt)
painless

Question 8

What would urine dipstick show in DKA?

Answer 8

Glucosuria
Ketonuria

Question 9

What would urine dipstick show in subacute bacterial endocarditis?

Answer 9

Proteinuria
Microscopic haematuria
(Splinter haemorrhages, janeway lesions)

Question 10

How would you investigate a patient with suspected renal stones?

Answer 10

CT-KUB
If unavailable: Abdo XR

Question 11

List 3 causes of hypercalcaemia

Answer 11

Primary Hyperparathyroidism (commonest in community)
Cancer (commonest in hospital)
Sarcoidosis

Question 12

List 3 causes of hypercalcaemia

Answer 12

Primary Hyperparathyroidism (commonest in community)
Cancer (commonest in hospital)
Sarcoidosis

Question 13

Which investigation can distinguish the cause of hypercalcaemia?

Answer 13

Plasma PTH

Question 14

How does PTH vary in the three causes of hypercalcaemia?

Answer 14

pHPT: HIGH/ N (endogenous production)
Cancer: LOW (endogenous production of PTHrP or bone invasion)
Sarcoid: LOW (excess Ca produced, suppresses PTH)

Question 15

What is the most common cause of primary hyperparathyroidism?

Answer 15

Benign parathyroid adenoma 85%
Uncontrolled release of PTH
Results in increased Ca2+

Question 16

PTH - it is released in response to…?
3 roles of PTH?

Answer 16

Low free Ca in serum
1. KIDNEY: stimulates 1-alpha-hydroxylase = (GUT: Ca + Pi absorption)
2. KIDNEY: Ca resorption + Pi excretion
3. BONE: activates osteoclast for Ca resorption

Question 17

How do calcium and urate stones differ on x-ray?

Answer 17

Calcium: Radio-OPAQUE
Urate: Radio-LUCENT

Question 18

Why do patients with hypercalcaemia get polyuria?

Answer 18

Calcium acts like glucose, water follows via osmosis
Causes Nephrogenic DI

Question 19

What ocular sign may be found in those with chronic hypercalcaemia?

Answer 19

Band keratopathy
Calcium deposits across the front of the eye

Question 20

List 5 complications of hypercalcaemia

Answer 20

Renal stones
Peptic ulcer disease
Pancreatitis
Skeletal changes
Osteitis fibrosa cystica (pepper-pot skull)

Question 21

Give 6 risk factors for renal stones

Answer 21

pHPT
Hypercalcaemia
Hypercalciuria (>6mmol/ day)
Dehdration
FH
Recurrent UTI

Question 22

Give 4 features of presentation of renal calcium stones

Answer 22

Pain (colic)
Haematuria
Recurrent infections
Renal failure

Question 23

Give 4 investigations for renal calcium stones

Answer 23

CT-KUB
Urine dip
Creatinine, U+Es, FBC, CRP, serum biochemistry
Stone analysis (composition)

Question 24

How are most renal stones managed?

Answer 24

Most pass
Painkillers: ibuprofen PO
If admitted: diclofenac IM

Question 25

Give 3 interventions for renal stones >5mm

Answer 25

Extra-corporeal shockwave lithotripsy (ESWL)
Ureteroscopy
Percutaneous nephrolithotomy

Question 26

Give 3 preventative measures against renal stones

Answer 26

Drink more water
Treat hypercalciuria: Thiazides (not in parathyroid adenoma- exacerbates hypercalcaemia)
Treat hypercalcaemia

Question 27

What is the urgent treatment for hypercalcaemia?

Answer 27

IV access + catheter
IV Saline 0.9% 1L 4-6h (1st bag 1L over 1h if severely dehydrated)
IV Frusemide: prevent oedema + aid calciuresis

Question 28

In which patients is a bisphosphonate appropriate for adding to their hypercalcaemia treatment? Which?

Answer 28

Hypercalcaemia of malignancy
(DONT give if pHPT)
IV Pamidronate 30-60mg

Question 29

What curative treatment can be performed in pHPT?

Answer 29

Parathyroidectomy

Question 30

In a patient with long standing hyperparathyroidism, what may be found on bone histology?

Answer 30

Brown tumours (cyst like area due to osteoclast resorption)
Consists of
Mutlinucleate giant cells, cellular fibrous stroma, macrophages

Question 31

What is sarcoidosis?

Answer 31

Systemic disease where macrophages express 1-alpha hydroxylase
primarily causes lung disease (fibrotic scarring around non-caseating granulomas)

Question 32

A 45y afrocaribean man presents with SOB, this CXR and non-caseating multinucleate giant cells on biopsy, what is the diagnosis?

Answer 32

Sarcoidosis

Question 33

What is unilateral vs bilateral hilarity lymphadenopathy suggestive of in a patient presenting with SOB?

Answer 33

Unilateral: Cancer
Bilateral: Sarcoidosis

Question 34

What happens if a sarcoidosis patient takes excess vitamin D/ in summer months?

Answer 34

Macrophages in lymph nodes in lung express 1 alpha hydroxylase (not regulated by PTH)
Vitamin D gets activated, become hypercalcaemic

Question 35

What is the treatment of sarcoidosis?

Answer 35

Steroids e.g. Prednisolone normalise calcium + suppress inflammation
Wean slowly +/- lifelong continuation at low doses to prevent reactivation