Clinical Chemistry CPC Flashcards
What is an alternative treatment to antidepressants?
CBT
What is St John’s Wort?
(Hypericum perforatum)
o Thought to be quite similar to paroxetine (an antidepressant)
o The St. John’s wort was moderately effective
What mood is hypercalcaemia associated with?
Depression/ tiredness
What is hypocalcaemia associated with?
irritability and fits
What are the heart affects of potassium?
o In hypokalaemia, your myocardium becomes more irritable -> leads to arrhythmias
o As potassium rises, myocardium becomes more stable, however, the ultimate stable rhythm = asystole
What are 3 important types of Fractures?
o Smith’s fracture = posterior displacement of the radius (i.e. radius towards the BACK of the hand)
Falling on a flexed wrist
Treated with manipulation under anaesthesia (MUA) and plaster
o Colle’s fracture = anterior displacement of the radius (i.e. radius towards the PALM of the hand)
Falling on an extended wrist
o Pott’s fracture = ankle fracture involving both tibia and fibula
Does Glomerulonephritis present with pain?
No
What are the differentials of abnormal urine dip?
Renal stones -> tear urothelium -> macroscopic haematuria
Glomerulonephritis -> microscopic haematuria (not overt)
DKA -> acidosis, ketonuria
Acute rheumatic fever -> proteinuria (or normal)
Subacute bacterial endocarditis -> microemboli, microscopic haematuria, splenomegaly
How do you investigate abdo pain with haematuria?
Plain abdominal XR -> calcified stones (can be confused with gallstones but better for renal colic)
USS abdomen -> nephrocalcinosis
How do you find out the cause for someones renal stones?
- Cancer (commonest in hospital)
- Primary HPT (commonest in community)
- Sarcoidosis
o N.B. do plasma calcium before PTH because you need the calcium level to interpret any PTH level
o [Ca2+] = 2.82 (2.20-2.60)
o PTH = 3.0 (1.1-6.8 pM)
o As PTH is normal -> primary HPT most likely
How do PTH and calcium behave in sarcoidosis, cancer and primary hyperparathyroidism?
- Sarcoid -> PTH suppression/low (as produces lots of calcium which suppresses PTH)
- Cancer -> PTH high (endogenous production) -> from PTHrP or invading bone cancer
- 1st HPT -> PTH normal/high (despite hypercalcaemia)
If PTH is not suppressed despite hypercalcaemia what is going on?
Endogenous PTH production
How often is the cause of hypercalcaemia with high PTH an adenoma?
85%
What are the actions of PTH?
Kidneys:
• Activate 1-alpha hydroxylase -> vitamin D activation ->
o Absorb calcium from gut
o Absorb phosphate from gut
- Directly resorb calcium
- Directly excrete phosphate
Bone:
• Activate osteoclasts
What are the features of hypercalcaemia?
o Moans, bones, groans and stones
Many can be asymptomatic
Calcium stones are radio-opaque, but urate stones are radio-lucent
o Polydipsia/polyuria (nephrogenic DI) calcium acts like glucose to carry water with it via osmosis
o Band keratopathy (calcium deposition across the front of the eye)
This is a feature of CHRONIC hypercalcaemia (so it cannot be hypercalcaemia of malignancy)
o Complications: Renal stones Peptic ulcer disease Pancreatitis Skeletal changes Osteitis fibrosa cystica (i.e. pepper-pot skull)
What are the risk factors for renal calcium stones?
FHx Dehydration Hypercalciuria Hypercalcaemia HPT Recurrent UTI
How would renal calcium stones present?
Pain
Haematuria
Recurrent infections (Proteus mirabilis)
Renal failure
What is the investigations for renal stones?
CT-KUB
Stone analysis
Urine and serum biochemistry
What is the management of renal stones?
Most stones will pass -> painkillers: • PR diclofenac is very good Lithotripsy Cystoscopy Lithotomy
How do you prevent renal stones?
Drink more water
Treat hypercalciuria (e.g. thiazides)
• Not in parathyroid adenoma -> hypercalcaemia (reduces calcinuria but increases serum Ca)
Treat hypercalcaemia
What is the management of hypercalcaemia?
IV 0.9% saline
IV frusemide
IV pamidronate 30-60mg (better if cancer)
How do you give fluid in hypercalcaemia?
- 4-hourly or 6-hourly bags of 1L 0.9% NaCl
* 1st bag of 1L given over 1 hour (if severely dehydrated)
Why do you give frusemide?
prevent pulmonary oedema and aid calciuresis
How do you give pamidronate?
IV pamidronate (bisphosphonate), 30-60mg
• Not given in all circumstances
• Do not take effect for around a week and is not given in all circumstances
• Hold off to begin with as you can’t measure serum calcium and phosphate if given
o Do NOT hold off if hypercalcaemia due to cancer
What is the non urgent treatment of hypercalcaemia?
Well hydrated
Avoid thiazides (reduce hypercalciuria but increase plasma calcium)
Surgery (parathyroidectomy)
- Technetium Sesta MIBI and USS performed -> shows hyperactive parathyroid
- If both tests concordant -> whole neck does NOT need to be opened
- If tests not concordant -> surgeon needs to view all four glands and take out the largest one
What may the hand X ray be like in HPT?
o Often be normal
o Later stages may show cystic changes in the radial aspect
What is the histology of HPT?
o Brown tumours = multinucleate giant cells
Activated osteoclasts in the bone
o Brown tumours = long-standing undiagnosed HPT
o I.E. Histology of the bone shows…
Brown tumours
Multinucleate giant cells
if high calcium and PTH normal, go for the parathyroids
if high calcium and PTH normal, go for the parathyroids
- 45yo, Afrocaribean man, SOB
- Most helpful investigation -> CXR -> bilateral hilar lymphadenopathy
- Histology of biopsy -> non-caseating granulomas
Diagnosis?
Sarcoidosis
What is the biochemistry in sarcoidosis?
- FBC -> [Ca2+] 2.82 (2.20-2.60)
* PTH suppressed to undetectable levels -> sarcoidosis picture
What is the treatment of sarcoidosis?
Steroids
What is the mechanism of hypercalcaemia in sarcoidosis?
‘Seasonal hyercalcaemia’
o Macrophages in the lungs express 1-alpha hydroxylase -> activate vitamin D
o Vitamin D leads to excessive calcium
o Patients more likely to become hypercalcaemic in summer months because of increased exposure to sunlight
MEN 1 or 2 can present with hypercalcaemia
MEN 1 or 2 can present with hypercalcaemia
What do potassium abnormalities do to the heart?
Hypokalaemia- VF
Hyperkalaemia- Asystole
Can PTH be normal in primary hyperparathyroidism?
Yes- inappropriately not suppressed
What is the rate limiting step in Vit D production?
1 alpha hydroxylase
What will the hand x ray of 1HPT show?
Radial aspect cystic changes
What are the symptoms of hypercalcaemia (HPT)?
Bones (fractures)
Stones (kidney)
Groans (psych)
Moans (abdo pain, pancreatitis)
What are looser’s zones linked to?
Vit D deficiency
How do giant cells get formed?
Failure of cell division adding nuclei to a single huge cell- can happen in many AI
What is the rate limiting step of Vitamin D production?
1 alpha hydroxylation
