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MedEd + PathSoc + Laz's Qs + Romesh Path > ChemPath 20: Clin Chem CPC > Flashcards

ChemPath 20: Clin Chem CPC Flashcards

1
Q

Describe the effect of hypokalaemia on the myocardium.

A

Increases myocardial irritability

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2
Q

Describe the cardiac consequences of plasma potassium being too high or too low.

A

Hypokalaemia – ventricular fibrillation

Hyperkalaemia – asystole (ultimate stable rhythm)

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3
Q

What is the difference between a Colles’ fracture and a Smith’s fracture?

A

Colles’ – fracture caused by falling on an outstretched hand. The radial head will be displaced backwards (away from the palm)

Smith’s – fracture caused by falling on a flexed wrist. The radial head will be displaced forwards (towards the palm)

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4
Q

What is a Pott’s fracture?

A

Ankle fracture involving the tibia and fibula

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5
Q

What would you expect to see on the urine dipstick of someone with subacute bacterial endocarditis?

A

Microscopic haematuria

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6
Q

What is the differential diagnosis for hypercalcaemia?

A

Cancer

Primary hyperparathyroidism

Sarcoidosis

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7
Q

What is the physiological role of PTHrP (Parathyroid hormone-related protein)?

A

Our genome encodes a gene for PTHrP

This is important in foetal life because it allows us to steal calcium from our mother to help form our skeleton

NOTE: PTHrP is also produced by the lactating breast
NOTE: PTHrP stimulates cancer cells to invade bone

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8
Q

What are the two main mechanisms of hypercalcaemia of malignancy?

A

PTHrP

Cancer invading bone

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9
Q

Main actions of PTH?

A

Increase calcium liberation from bone (osteoclast activity)

Increase calcium reabsorption in the kidneys

Increase calcium absorption in the intestines

Activates 1-alpha hydroxylase in the kidneys (thereby increasing activation of vitamin D)

Increase phosphate excretion

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10
Q

Name and describe an eye sign of hypercalcaemia

A

Band keratopathy – calcium deposition across the front of the eye

It is a feature of chronic hypercalcaemia (i.e. it will not be caused by hypercalcaemia of malignancy)

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11
Q

What is a key difference between calcium stones and urate stones?

A

Calcium stones are radio-opaque

Urate stones are radiolucent

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12
Q

List some complications of hypercalcaemia.

A

Renal stones

Pancreatitis

Peptic ulcer disease

Skeletal changes (osteitis fibrosa cystica)

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13
Q

List some risk factors for hypercalcaemia.

A

Family history

Dehydration

Hyperparathyroidism

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14
Q

Which bacterium has a predilection to infect urinary tract stones?

A

Proteus mirabilis

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15
Q

What are the main investigations used for urinary tract stones?

A

CT-KUB w/out contrast

Stone analysis

Urine and serum biochemistry

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16
Q

What are some management options for urinary tract stones?

A

Lithotripsy

Lithotomy

Cystoscopy

17
Q

Urinary tract stone prevent?

A 
Drink more water 
Treat hypercalciuria (thiazides)

NOTE: loop diuretics increase urine calcium

18
Q

At what point would you use emergency management of hypercalcaemia?

A

When serum calcium > 3 mmol/L or very unwell (e.g. dehydrated, confused, drowsy, seizures)

19
Q

Outline the emergency management of hypercalcaemia.

A

IV access
Insert catheter

3-6 L 0.9% saline over 24 hours

The first litre should be given quickly (over 1 hour) to correct dehydration

Elderly patients should also be given furosemide (to prevent pulmonary oedema)

20
Q

Which other drug may be used under desperate circumstances when managing hypercalcaemia?

A

Pamidronate (IV) - bisphosphonate

Good at treating bone pain but takes at least 1 week to start working and gets incorporated into bone for a very long time

21
Q

In which group of patients would you use dextrose rather than saline (in hypercalcaemia mx)?

A

Liver failure – they have a tendency to retain salt

22
Q

Outline the treatment of non-emergency hypercalcaemia.

A

Keep well hydrated

Avoid thiazides (they reduce hypercalciuria but they increase plasma calcium concentration)

Surgery

23
Q

What is minimally invasive parathyroidectomy?

A

A technetium sesta MIBI scan shows a hyperactive parathyroid

An USS is also performed and if the results of the sesta MIBI and USS are concordant, the whole neck does not need to be opened

If they are not concordant, the surgeon will need to view all four glands and take out the largest one

24
Q

What feature may you see on an X-ray of the hands in a patient with primary hyperparathyroidism?

A

Cystic changes in the radial aspect

25
Q

What is a characteristic histological feature of long-standing undiagnosed hyperparathyroidism?

A

Brown tumours – they are multinucleated giant cells in the bone. The giant cells are activated osteoclasts

26
Q

What is the mainstay of treatment of sarcoidosis?

A

Steroids

27
Q

What is the histological hallmark of sarcoidosis?

A

Non-caseating granulomas

28
Q

Outline the mechanism of hypercalcaemia in sarcoidosis.

A

Macrophages in the lungs express 1-alpha hydroxylase

This activates vitamin D

NOTE: patients are more likely to become hypercalcaemic in the summer months because of increased exposure to sunlight

29
Q

A 35 year old woman presents with right loin-to-groin pain. She describes this as 10/10 in severity. A urine dipstick is performed which shows the following:

Leukocytes +ve
Nitrites –ve
Glucose –ve
Blood +ve

What is the most likely cause?

Cystitis
Pyelonephritis
Renal stones
Bladder cancer
Diabetes mellitus

A

Renal stones - Loin to groin + absence of nitrites suggests this

30
Q

Most appropriate ix for renal stones?

A

CT KUB (w/out contrast)

AXR- may be useful some stones are radiolucent
CT KUB w/ contrast - less sensitive

31
Q

Most common composition of renal stones? What about composition of those most likely to cause stag horn calculi (bilateral esp)?

A

Most common - Calcium oxalate

Staghorn - Struvite (magnesium ammonium phosphate)

32
Q

What organism are struvite renal stones associated w/?

A

Proteus mirabilis

33
Q

A 55 year old man presents to A&E with loin-to-groin pain. A CT KUB identifies a right 7mm obstructing stone in the renal pelvis. His blood results are below:

Raised Ca, Urea, Creatinine
Low Phosphate
Normal ALP and PTH

What is the most likely underlying cause?

A

PTH is inappropriately normal - even though high Ca

Deranged U+Es due to post-renal AKI

Hence this is caused by Primary hyperparathyroidism

34
Q

What are some conditions that cause HIGH Ca?
What is the Ca, phosphate, PTH and ALP like in these conditions?

A

Primary hyperPTH

  • Raised Ca
  • Low Phosphate
  • Raised / Normal PTH
  • Normal ALP

Tertiary hyperPTH

  • Raised Ca
  • Raised Phosphate
  • Raised PTH
  • Normal ALP

Malignancy

  • Raised Ca
  • Normal Phosphate
  • Low PTH
  • Normal ALP
35
Q

What are some conditions that cause NORMAL Ca?
What is the Ca, phosphate, PTH and ALP like in these conditions?

A

Osteoporosis

  • Normal Ca
  • Normal Phosphate
  • Normal PTH
  • Normal ALP (can be raised if fracture)

Pagets Disease

  • Normal Ca
  • Normal Phosphate
  • Normal PTH
  • Raised ALP

Pseudo-pseudohypoPTH

  • Normal Ca
  • Normal Phosphate
  • Normal PTH
  • Normal ALP
36
Q

What are some conditions that cause LOW Ca?
What is the Ca, phosphate, PTH and ALP like in these conditions?

A

Secondary hyperPTH

  • Low Ca
  • Low (if vit D deficient) / Raised (if CKD) Phosphate
  • Raised PTH
  • Raised ALP

PseudohypoPTH

  • Low Ca
  • Raised Phosphate
  • Raised PTH
  • Normal ALP
37
Q

A 55 year old man presents to A&E with loin-to-groin pain. His calcium is 3.05 and he has a renal stone.

What is the most appropriate 1st line management option?

A

IV Fluids - 0.9% NaCl, 4+ litres daily

38
Q

A 45 year old Afro-Caribbean woman presents to A&E with loin-to-groin pain. She also has tender, erythematous nodules on both her shins, which she’s had for 1 week. Her blood results are shown below:
Raised Ca
Low PTH

Which enzyme is activated by her underlying condition to cause hypercalcaemia?

A

1a-hydroxylase

Sarcoidosis w/ erythema nodosum

Macrophages in sarcoidosis’ non-caseating granulomas produce 1a-hydroxylase which activates vit D

MedEd + PathSoc + Laz's Qs + Romesh Path (99 decks)

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