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Pathology > Chemical Pathology > Flashcards

Chemical Pathology Flashcards

0
Q

How do you calculate osmolality?

A 
Osmolality = 2 (Na+K) + Urea + Glucose
Units = mosm/kg
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1
Q

pH 6.85
pCO2 2.3 kPa
PO2 15 kPa
What is the acid base abnormality?

A

Metabolic acidosis

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2
Q

How is the anion gap calculated?

A

Anion gap = Na + K - Cl - bicarb

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3
Q

What is a normal anion gap?

A

18 mM

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4
Q 
pH 7.65
pCO2 2.8 kPa
Bicarb 24 mM (normal)
PO2 15 kPa
What is the acid base abnormality?
A

Respiratory alkalosis

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5
Q 
pH 7.10
pCO2 1.3 kPa
PO2 15 kPa
What is the acid base abnormality?
With an anion gap of 50, what could be causing this?
A

Metabolic acidosis.
Could be ketones but if negative could be methanol, ethanol, lactate.
Metformin in overdose can cause a lactic acidosis.

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6
Q

Which diabetic drug in overdose can cause a lactic acidosis?

A

Metformin

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7
Q

What is plasma?

A

Supernatant of unclotted blood. Serum in the supernatant of clotted blood.

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8
Q

What is the normal total protein range of plasma?

A

60-80 g/L

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9
Q

Examples of alpha-1 globulins

A

Alpha-1-antitrypsin

Alpha-1-acid Glycoprotein

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10
Q

Examples of alpha-2 globulins

A

Haptoglobin
Caeruloplasmin
Alpha-2-macroglobulin

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11
Q

Examples of Beta globulins

A

Transferrin
Apo B
Complement

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12
Q

Examples of gamma globulins

A

IgG, IgA, IgM, IgD, IgE

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13
Q

What is the normal plasma concentration of albumin? How does it change in disease?

A

33-47 g/L

Almost always low in disease, increase only seen in severe dehydration.

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14
Q

How do Kwashiorkor and Marasmus differ?

A

Kwashiorkor: Sufficient calorie intake, but with insufficient protein consumption characterized by oedema, irritability, anorexia, ulcerating dermatoses, and an enlarged liver with fatty infiltrates.
Marasmus: inadequate energy intake in all forms, including protein. Look emaciated.

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15
Q

What are the three main reasons behind a low albumin?

A

Decreased production
Increased extra vascular loss
Increased GI and renal loss

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16
Q

What is alpha-1-antitrypsin?

A

Major antagonist of serine proteases including neutrophil elastase. Positive acute phase reactant

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17
Q

What does haptoglobin do?

A

Binds free haemoglobin and transports it to the spleen.

There are low levels in haemolysis.

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18
Q

What is caeruloplasmin and what disease is associated with it?

A

Copper containing protein.
Autosomal recessive deficiency causes Wilsonā€™s disease - body retains copper in tissues resulting in liver disease, neurological and psychiatric problems, haematological disorders.

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19
Q

What does transferrin do?

A

Plasma iron transport, negative acute phase protein.

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20
Q

A defect in HFE gene causes what disease?

A

Hemochromatosis - membrane protein regulating iron absorption affected causing multisystem iron deposition.
Diabetes, cirrhosis, gonadal/pituitary failure, cardiomyopathy, arthritis, bronzing of skin.

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21
Q

Pepperpot skull X-ray sign is associated withā€¦?

A

Myeloma

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22
Q

What tumours are associated with raised alpha-feto protein (AFP)?

A

Hepatocellular carcinoma, germ cell tumors, and metastatic cancers of the liver.

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23
Q

What tumours are associated with raised Ca 19-9?

A

Pancreatic cancer - levels measured to monitor response to treatment

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24
Q

What tumours are associated with Ca-125?

A

Ovarian cancer

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25
Q

What tumours are associated with carcinoembryonic antigen (CEA)?

A

Colorectal carcinoma

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26
Q

What tumours are associated with Beta-HCG?

A

Testicular cancer.
Seminoma, choriocarcinoma, germ cell tumors, hydatidiform mole formation, teratoma with elements of choriocarcinoma, and islet cell tumor.

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27
Q

Oligoclonal IgG in CSF may be seen in what?

A

Demyelinating diseases and some infections

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28
Q

What are the protein levels of transudates and exudates?

A

Transudate protein < 25 g/L

Exudate protein > 35 g/L

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29
Q

How does the pattern of renal disease affect protein excretion?

A

Glomerular: albumin
Tubular: retinal binding protein and beta-2-microglobulin
Overflow: paraprotein e.g. in myeloma

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30
Q

What are the causes of a transudate?

A

CCF
Liver failure
Hypoalbuminaemia (nephrotic syndrome)
Peritoneal dialysis

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31
Q

What are the causes of an exudate?

A

Parapneumonic effusions
Malignancy
Pulmonary embolism
Pancreatitis, RA, SLE, TB

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32
Q

An exudate with protein >40 g/L is very likely caused by what?

A

Pancreatitis

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33
Q

How do you calculate the SAAG?

A

Serum ascites-albumin gradient (SAAG)

= serum albumin - ascites albumin

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34
Q

What are Lightā€™s criteria?

A

Pleural / serum protein >0.5
Pleural / serum LDH >0.6
Pleural LDH >ā…” times the normal upper limit for serum
2 of 3 = exudate

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35
Q

What does the SAAG value suggest? What are the cut-offs?

A 
High gradient (>11 g/L) = TB, malignancy, pancreatitis
Low gradient (<11 g/L) = cirrhosis, nephrotic syndrome
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36
Q

The levels of which protein fall during intravascular haemolysis?

A

Haptoglobin

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37
Q

What can deficient enzyme activity lead to?

A

Lack of end product
Build-up of precursors
Abnormal, often toxic metabolites

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38
Q

What are Wilsonā€™s criteria for screening?

A

1) The condition should be an important health problem.
2) There should be a treatment for the condition.
3) Facilities for diagnosis and treatment should be available.
4) There should be a latent stage of the disease.
5) There should be a test or examination for the condition.
6) The test should be acceptable to the population.
7) The natural history of the disease should be adequately understood.
8) There should be an agreed policy on whom to treat.
9) Economically balanced.
10) Case-finding should be a continuous process, not just a ā€œonce and for allā€ project.

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39
Q

What causes PKU?

A

Phenylketonuria (PKU) is caused by a phenylalanine hydroxylase deficiency which leads to raised levels of phenylalanine in the blood.

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40
Q

How is congenital hypothyroidism screened for in newborns?

A

TSH measured from blood spot on Guthrie card.

Only 15% inherited, usually dysgenesis/agenesis of thyroid.

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41
Q

How is cystic fibrosis screened for in newborns?

A

Immune reactive trypsinogen (IRT) blood levels are increased. Confirmed with sweat test.

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42
Q

How is MCADD screened for in newborns?

A

Medium chain AcylCoA dehydrogenase screened for using acylcarnitine levels by tandem mass spectrometry

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43
Q

What is the acute management for an alert and orientated adult with hypoglycaemia?

A

Give oral carbohydrates;
Rapid e.g. Lucozade
Longer acting e.g. sandwich
Consider glucagon if deteriorating, refractory or insulin induced.

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44
Q

What is the acute management for a drowsy, confused adult with hypoglycaemia but with an intact swallow?

A

Buccal glucose e.g. Hypostop, glucogel etc.

Start thinking about IV access and consider glucagon IM/SC

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45
Q

What is the acute management for an unconscious adult with hypoglycaemia?

A

IV access, 50 ml, 50% glucose or 100 ml 20% glucose.

Consider glucagon if deteriorating, refractory, insulin induced or difficult IV access.

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46
Q

What are the symptoms of hypoglycaemia?

A

Adrenergic: tremors, palpitations, sweating, hunger
Neuroglyopaenic: somnolence, confusion, incoordination, seizures, coma
May be none!

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47
Q

What are the main effects of natural glucagon?

A
  • reduce peripheral uptake of glucose
  • increase glycogenolysis
  • increase gluconeogenesis
  • increase lipolysis
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48
Q

How does the brain respond to hypoglycaemia? (Hormonally)

A

Sensed in hypothalamus, activates sympathetic system (catecholamines) and stimulates ACTH and GH production

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49
Q

What regulates ketone body production?

A

Beta-oxidation very sensitive to insulin levels, must be low for ketone production

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50
Q

What is muscle glycogen broken down to?

A

Glucose-6-phosphate which canā€™t be exported to raised glucose levels in hypoglycaemia.

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52
Q

What are the problems with measuring blood glucose?

A

Blood glucose meter has poor precision at low glucose levels and the devices are often poorly maintained. Lab measured venous blood glucose much better but there is a delay in results.

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53
Q

What diabetic drugs are common culprits of hypoglycaemic events?

A

Sulphonylureas (esp. long acting), insulin (long acting can cause hypoā€™s at night) and also beta-blockers, salicylates and alcohol.

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54
Q

What can C-peptide levels tell you?

A

It is a good marker of beta-cell function and can help to differentiate the cause of hypoglycaemia. Blood sample must be placed on ice for accurate reading. C-peptide is fragment left after proinsulin is cleaved to release insulin. Half-life ~30mins, renal clearance

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55
Q

What may a very good HbA1c level suggest?

A

Patient may be having recurrent hypoā€™s

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56
Q

What might a patient with lanugo hair on their back have?

A

Anorexia nervosa - due to malnourishment. Very fine, soft, unpigmented hair usually only seen on fetuses.

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57
Q

A large disparity between finger prick measured glucose (4.0) and blood glucose (2.5) at the low end of the scale might be caused by what?

A

Sugar or something sweet on the finger from where the finger prick sample was taken raising the level. Possible in anorexics trying to hide low blood sugar.

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58
Q

What does a low blood glucose, low insulin and low C-peptide suggest?

A

Appropriate response to hypoglycaemia caused by starvation, exercise, illness, liver failure and endocrine deficiencies e.g. hypopituitarism, adrenal failure

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59
Q

What is beta-hydroxybutyrate?

A

A ketone body. Should be produced from fatty acid oxidation in hypoglycaemia. Others are acetoacetate and acetone.

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60
Q

What could cause a neonate to have hypoglyaemia and negative ketones?

A

A fatty acid oxidation defect. Free fatty acids would be raised.

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61
Q

What may cause a hypoglycaemia and a endogenous high insulin level?

A

Iselet cell tumours (insulinoma)
Sulphonylurea abuse
Islet cell hyperplasia: infant of diabetic mother, Beckwith Weidemann syndrome, nesidioblastosis.

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62
Q

What type of tumour is an insulinoma?

A

Usually small solitary adenoma
10% malignant
8% associated with MEN1

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63
Q

A child fitting with a low glucose, high insulin and low C-peptide is caused by what?

A

Factitious insulin

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64
Q

What might cause an elderly smoker to have refractory hypoglycaemia with low insulin, low C-peptide, low FFA and low ketones?

A

Non-islet cell tumour hypoglycaemia - paraneoplastic syndrome, secretion of big IGF-2 which binds to and activates IGF-1 and insulin receptor, acting as insulin.

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65
Q

An adult female with a low glucose, high insulin and low C-peptide could be caused by what?

A

Factitious insulin

Antibodies to insulin receptors - bind and stimulate insulin release - IR-Ab present.

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66
Q

Which non-diabetic drugs could cause hypoglycaemia?

A

Quinine - stimulates insulin secretion

Pentamidine - toxic to Beta-cells, releases pre-formed insulin

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67
Q

What is reactive/post-prandial hypoglycaemia?

A

Low blood glucose following food intake. Can occur following gastric surgery, with hereditary fructose intolerance, early DM.

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68
Q

X-linked urea cycle disorder?

A

Ornithine transcarbamylase deficiency

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69
Q

Flags for urea cycle disorders?

A
  • Vomiting without diarrhoea
  • Respiratory alkalosis with hyperammonaemia
  • Neurological encephalopathy (incl. ADHD)
  • Protein rich food avoidance, change in diet
    Majority autosomal recessive inheritance
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70
Q

A patient with hyperammonaemia, a metabolic acidosis and a high anion gap might have what?

A

An organic aciduria - a group of metabolic disorders which disrupt normal amino acid metabolism, particularly branched-chain amino acids (leucine, isoleucine, valine), causing a buildup of acids which are usually not present

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71
Q

Presentation of an organic aciduria?

A

Presents in neonates:

  • unusual odour (e.g. urine), lethargy, feeding problems
  • truncal hypotonia / limb hypertonia, myoclonic jerks
  • Hyperammonaemia + metabolic acidosis + high anion gap (not lactate)
  • Hypocalaemia, neutropenia, thrombopenia, pancytopenia
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72
Q

What is Reyeā€™s syndrome?

A

Classic features: rash, vomiting, liver damage.
Also lethargy, confusion, seizures, decerebration, respiratory arrest, hypoglycaemia.
Can be triggered by salicylates (aspirin), antiemetics, valproate.
Associated with underlying inborn metabolic disorder - require screening

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73
Q

How does a chronic intermittent form of an organic aciduria present?

A

In childhood (rather than neonatal) with recurrent episodes of ketoacidotic coma, cerebral abnormalitites and Reyeā€™s syndrome

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74
Q

What tests should you do in a patient with suspected Reye syndrome?

A
  • Plasma ammonia
  • Plasma / urine amino acids
  • Urine organic acids
  • Plasma glucose and lactate
  • Blood spot carnitine profile
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75
Q

What does hypoketotic hypoglycaemia suggest?

A

A fatty-acid metabolism disorder.

Get hepatomegaly and cardiomyopathy.

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76
Q

What is galactosaemia and what is the most common form?

A

Disorder of galactose metabolism.
Galactose-1-phosphate uridyl transferase (Gal-1-PUT) most common and most severe.
Raised gal-1-phosphate causes liver and kidney disease.

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77
Q

How does galactosaemia present?

A

In neonates with vomiting, diarrhoea, conjugated hyperbilirubinaemia, hepatomegaly, hypoglycaemia and sepsis (E.coli)

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78
Q

If galactose is not removed from the diet of patients with galactosaemia, what occurs?

A

Galactitiol is formed by the action of aldolase on gal-1-phosphate leading to bilateral cateracts

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79
Q

How can you test for galactosaemia?

A
  • Urine reducing substances

- Red cell Gal-1-PUT

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80
Q

What is glycogen storage disease type 1 also know as and what is the deficiency?

A

von Gierkeā€™s disease
Deficiency of glucose-6-phosphatase - unable to break down glycogen to glucose in liver results in increased glycogen storage in liver and kidneys.

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81
Q

What signs does someone with glycogen storage disease type 1 get?

A

Hepatomegaly, nephromegaly, hypoglycaemia, lactic acidosis and neutropenia

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82
Q

How can a mitochondria disorder present?

A

Can affect any organ, any age, and by any mean of inheritance.

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83
Q

3 examples of a mitochondrial disorder?

A

Barth syndrome
MELAS syndrome
Kearns-Sayre syndrome

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84
Q

What is Barth syndrome?

A

Mitochondrial disorder presenting from birth with cardiomyopathy, neutropenia and myopathy

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85
Q

What is MELAS syndrome?

A

Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes - presents in childhood ~5-15 years

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86
Q

What is Kearns-Sayre syndrome?

A

Mitochondrial disorder presenting between ages 12-30 with chronic progressive external opthalmoplegia, retinopathy, deafness and ataxia

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87
Q

How should suspected mitochondrial disorders be investigated?

A
  • Fasting lactate (elevated)
  • CSF lactate / pyruvate
  • CSF protein
  • CK
  • Muscle biopsy
  • Mitochondrial DNA analysis
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88
Q

What pathology is associated with congenital disorders of glycosylation?

A

Cardiomyopathy, osteopenia, hepatomegaly, dysmorphic features e.g. inverted nipples and subcutaneous fat pads.
Test: analysis of transferrin glycosylation status

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89
Q

What are peroxisomal disorders?

A

Disorder in the metabolism of very long chain fatty acids and biosynthesis of complex phospholipids

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90
Q

What problems occur with peroxisomal disorders?

A

Neonates:
- Severe muscular hypotonia and seizures
- Hepatic dysfunction with mixed hyperbilirubinaemia
- Dysmorphic signs
Infants:
- Retinopathy, sensorineural deafness, mental deficiency
- Hepatic dysfunction
- Late closing large fontanelle, long bone osteopenia, patella calcified stippling

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91
Q

What are lysosomal storage diseases?

A

Causes intraorganelle substrate accumulation leading to organomegaly with consequent dysmorphia and regression.

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92
Q

What lab investigations are done to confirm a lysosomal storage disease?

A
  • Urine mucopolysaccharides and/or oligosaccharides

- Leucocyte enzyme activites

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93
Q

How are lysosomal storage diseases treated?

A
  • Bone marrow transplant

- Exogenous enzyme replacement therapy

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94
Q

Definition of intermediary metabolism

A

Enzyme-catalysed processes within cells that extract energy from nutrient molecules and use that energy to construct cellular components

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95
Q

List of normal liver functions

A 
Intermediary Metabolism
Protein Synthesis
Xenobiotic Metabolism
Hormone Metabolism
Bile Synthesis
Reticulo-endothelial
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96
Q

Which two enzymes are contained within the cytoplasm of hepatocytes and measured as part of LFTs? And which one of them rises more in alcohol and cirrhosis?

A 
Alanine transferase (ALT)
Aspartate transaminase (AST)
AST rises more in alcohol and cirrhosis
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97
Q

Where is gamma-glutaryl transpeptidase (GGT) found in the liver? And when raised, what is it most commonly a sign of?

A

Hepatocytes and epithelium of small bile ducts.

Elevated in chronic alcohol use but also raised in bile duct disease and hepatic metastasis.

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98
Q

Which LFT enzyme is located in sinusoidal and canalicular membranes? And what causes it to become elevated?

A 
Alkaline phosphatase (ALP)
Markedly elevated if obstructive jaundice or bile duct damage.
Less elevated in viral hepatitis or alcoholic liver disease i.e. hepatocyte damage.
Other causes of a rise include bone disease (especially metastatic and pregnancy)
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99
Q

What is the best function of liver function?

A

Pro-thrombin time (due to short half-life of clotting proteins)

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100
Q

What should a urine dipstick show with normal liver function?

A

No bilirubin, small amount of urobilinogen.

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101
Q

When is urobilinogen not detected on a urine dipstick?

A

In there is extra-hepatic biliary obstruction. Will also have pale stools and dark urine with high conc of bilirubin.

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102
Q

What test should be ordered if LFTs are abnormal with a raised bilirubin?

A

Liver USS to look for dilated ducts or not.

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103
Q

What other liver function tests are there other than the standard LFTs?

A
  • Dye tests (indocyanine green / bromsulphalein)
  • Breath tests (aminopyrine / galactose)
  • Serum bile acids (elevated esp. in cholestatsis of pregnancy and PBC/PSC)
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104
Q

What happens LFTs when a patient with Gilberts syndrome fasts?

A

Get a raised unconjugated bilirubin

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105
Q

Which particular commonly used drug can cause cholestatic jaundice?

A

Augmentin, also flucloxacillin, erythromycin and many other drugs

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106
Q

What is Courvoisierā€™s sign/law?

A

In the presence of a painless palpable gallbladder, jaundice is unlikely to be caused by gall stones.

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107
Q

What 3 three can causes ALT and AST to go about 1000?

A

Viruses
Drugs
Ischaemia

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108
Q

What picture is common with LFTs in alcoholic liver disease?

A

AST:ALT = 2:1

In viral liver disease AST:ALT <1:1

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109
Q

Where are and what do the different zones of the adrenal glands do?

A 
From outside to in:
Capsule
Glomerulosa - Aldosterone
Fasiculata - Cortisol
Reticularis - Testosterone
Medulla - Adrenaline
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110
Q

31 year old presents with profound tiredness. Acutely unwell a few days. Vomiting.
Na: 125, K: 6.5, U 10, Glucose 2.9mM.
FT4 < 5nM TSH > 50mU/l
Whatā€™s the diagnosis?

A

Thyroid failure - Primary hypothyroidism plus mineralocoricoid and glucocorticoid deficiency - Addisonā€™s disease
= Schmidtā€™s syndrome aka Autoimmune polyendocrine syndrome type 2

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111
Q

What is Schmidtā€™s syndrome?

A

Aka Autoimmune polyendocrine syndrome type 2

Addisonā€™s disease, hypothyoidism and diabetes type I - occur together more commonly than by chance alone.

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112
Q

What is the test for Addisonā€™s disease?

A

Short synacthen test - compares cortisol levels before and after 250 mg of tetracosactide (syn ACTH). Check at 30 and 60 mins, should see a steady rise if no adrenal failure.

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113
Q

Differential for a 32 year old man with hypertension and an adrenal mass?

A

Phaeochromocytoma - large tumour
Connā€™s syndrome - small tumour
Cushingā€™s syndrome

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114
Q

What urgent drug treatment is required for a patient newly diagnosed with a phaeochromocytoma?

A

Alpha-blockade e.g. Phenoxybenzamine + fluids to prevent hypotension.
Later add beta-blockade then prepare for curative surgery.

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115
Q 
Hypertensive 33 year old.
Na 147,  K 2.8,  U 4.0.  Glucose 4.0 mM
Plasma aldosterone raised.
Plasma renin suppressed.
What is the diagnosis ?
A

Connā€™s syndrome - primary hyperaldosteronism

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116
Q

34 year old obese woman with type 2 diabetes, presents with hypertension and bruising.
Na: 146, K: 2.9, U 4.0, Glucose 14.0
Aldosterone <75 (low). Renin low. Diagnosis?

A

Cushingā€™s syndrome

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117
Q

Which dynamic test is used for Cushingā€™s syndrome?

A

Dexamethasone suppression test

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118
Q

What are the causes of Cushingā€™s syndrome?

A

Exogenous steroids
Pituitary dependent Cushings disease (85%)
Ectopic ACTH (5%)
Adrenal adenoma (10%)

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119
Q

An obese 35 year old patient has the following results:
9am cortisol (Monday): 650 nM
Given 0.5 mg dexamethasone every 6 hours for 48 hours
9am cortisol (Wednesday)

A

Normal obese person - reassure and discharge

120
Q

9am cortisol (Monday): 650 nM
Given 0.5 mg dexamethasone every 6 hours for 48 hours
9am cortisol (Wednesday) 500nM
What is the diagnosis?

A

Cushingā€™s syndrome of indeterminate cause.
Need to do high dose dexamethasone suppression test to distinguish between Pituitary dependent Cushingā€™s disease and Ectopic ACTH syndrome

121
Q

If raised cortisol levels are suppressed by 50% or more, by high dose dexamethasone, what is the diagnosis?

A

Pituitary dependent Cushingā€™s disease

122
Q

What is a normal GFR?

A

120 ml/min

Age-relaqted decline ~1 ml/min per year

123
Q

What is the gold standard measurement of GFR?

A

Inulin clearance - required steady state infusion, research tool only

124
Q

Factors which limit the use of serum creatinine as a marker of GFR?

A

Related to muscle mass
Actively secreted into urine by tubular cells causes overestimation
Generation differs with age, sex, race

125
Q

Equations used to refine endogenous markers

A

Cockcroft Gault - estimates creatinine clearance (not GFR)

MDRD - estimates GFR but may underestimate if above-average weight and young

126
Q

Calcium oxalate crystals in the urine can be caused by what?

A
  • most common constituent of human kidney stones

- one of the toxic effects of ethylene glycol poisoning

127
Q

What are muddy brown casts in the urine a sign of?

A

Acute tubular necrosis

128
Q

What are red blood cell casts strongly indicative of?

A

Glomerular damage and haemorrhage.

129
Q

You admit a 28 year old man who you suspect has a renal stone, what is your first choice of imaging?

A

CT

130
Q

What is the hallmark of pre-renal acute kidney injury?

A

Reduced renal perfusion (generalised hypotension or selective renal ischaemia)
No structural abnormality

131
Q

Causes of pre-renal AKI?

A
  • True volume depletion
  • Hypotension
  • Oedematous states
  • Selective renal ischaemia - RAS
  • Drugs affecting glomerular blood flow (NSAIDs, ACEI, Diuretics, Calcineurin inhibitors)
132
Q

How do NSAIDs and Calcineurin inhibitors precipitate pre-renal AKI?

A

Decrease afferent arteriolar dilatation

133
Q

How do ACEI or ARBs precipitate pre-renal AKI?

A

Decrease efferent arteriolar constriction

134
Q

How do pre-renal AKI and acute tubular necrosis differ?

A

Pre-Renal AKI is not associated with structural renal damage and responds immediately to restoration of circulating volume where as ATN does not respond.

135
Q

What is the hallmark of post-renal acute kidney injury? Examples?

A

Physical obstruction to urine flow

  • (Intra-renal obstruction)
  • Ureteric obstruction (bilateral)
  • Prostatic / Urethral obstruction
  • Blocked urinary catheter
136
Q

What occurs with prolonged obstructive uropathy?

A

Glomerular ischaemia
Tubular damage
Long term interstitial scarring

137
Q

What groups of intrinsic renal disease are there?

A

Vascular
Glomerular
Tubular
Interstitial

138
Q

What are there causes of acute renal injury with direct tubular injury?

A 
Most commonly ischaemic 
Endogenous toxins - myoglobin, immunoglobulins
Exogenous toxins - contrast, drugs
- Aminoglycosides
- Amphotericin
- Acyclovir
139
Q

What system is used to help stage acute kidney injury?

A 
RIFLE classification
(risk, injury, failure, loss, ESRD)
140
Q

How is stage 5 chronic kidney disease defined?

A

End-stage renal disease

GFR < 15 or on dialysis

141
Q

How is stage 1 chronic kidney disease defined?

A

Kidney damage with normal GFR > 90

142
Q

Common causes of chronic kidney disease

A
  • Diabetes
  • Atherosclerotic renal disease
  • Hypertension
  • Chronic Glomerulonephritis
  • Infective or obstructive uropathy
  • Polycystic kidney disease
143
Q

What are the consequences of chronic kidney disease?

A 
1]Progressive failure of homeostatic function
	-Acidosis	-Hyperkalaemia
2]Progressive failure of hormonal function
	-Anaemia	-Renal Bone Disease
3]Cardiovascular disease
	-Vascular calcification
	-Uraemic cardiomyopathy
4]Uraemia and Death
144
Q

How does CKD affect the acid-base status and how is it managed?

A

Metabolic acidosis due to failure of renal excretion of protons
Treated by oral sodium bicarbonate

145
Q

What is a major cause of hyperkalaemia in patients with CKD?

A

Dietary intake and drugs (ACEI, Spironolactone)

High potassium levels are found in foods such as milk, chocolate, dried fruits and tomatoes.

146
Q

What ECG changes can be observed with hyperkalaemia?

A
  • Tall peaked T waves
  • Loss/flattening of P wave
  • Widened QRS complex
147
Q

What type of anaemia is caused by CKD?

A

Normochromic, normocytic anaemia
Due to progressive decline in erythropoietin-producing cells with loss of renal parenchyma.
Usually noted when GFR<30

148
Q

How does CKD affect the bones?

A

Renal bone disease - reduced bone density, bone pain, fractures:

  • Osteitis fibrosa
  • Osteomalacia
  • Adynamic bone disease
  • Mixed osteodystrophy
149
Q

What is the underlying problem with osteitis fibrosa?

A

Hyper-parathyroidism

Causes osteoclastic resorption of calcified bone and replacement by fibrous tissue

150
Q

What can drug directly suppresses PTH?

A

Cinacalcet

151
Q

How can renal bone disease be treated?

A 
Phosphate control
	-Dietary
	-Phosphate binders
Vit D receptor activators
	-1alpha calcidol
	-Paricalcitol
Direct PTH suppression
	-Cinacalcet
152
Q

How do renal vascular lesions differ from traditional atheroma?

A

Renal vascular lesions are frequently characterised by heavily calcified plaques, rather than traditional lipid-rich atheroma.

153
Q

Which hormones are involved in renal regulation of potassium?

A

Angiotensin II

Aldosterone

154
Q

What is a normal serum concentration of potassium?

A

3.5-5.0 mmol/L

155
Q

Which cells does aldosterone act on?

A

Principal cells of the cortical collecting tubule

156
Q

What effect does aldosterone have on kidney cells?

A

Aldosterone increases no. open Na+ channels in the luminal membrane, increasing Na+ reabsorption and hence K+ secretion

157
Q

What are the stimuli for aldosterone secretion?

A

Angiotensin II

Potassium

158
Q

What are the main causes of hyperkalaemia?

A
  • Renal impairment: reduced renal excretion
  • Drugs: ACE inhibitors, ARBs, spironolactone
  • Low Aldosterone: Addisonā€™s disease, Type 4 renal tubular acidosis (low renin, low aldosterone)
  • Release from cells: rhabdomyloysis, acidosis
159
Q

How would you manage a patient with hyperkalaemia?

A
  • 10 ml 10% calcium gluconate
  • 50 ml 50% dextrose + 10 units of insulin
  • Nebulized salbutamol
  • Treat the underlying cause
160
Q

What are the causes of hypokalaemia?

A
  • GI loss
  • Renal loss: hyperaldosteronism (excess cortisol), increased sodium delivery to distal nephron, osmotic diuresis
  • Redistribution into the cells: insulin, beta-agonists, alkalosis
  • Rare causes: Renal tubular acidosis type 1& 2, hypomagnesaemia
161
Q

What are the clinical features hypokalaemia?

A

Muscle Weakness
Cardiac arrhythmia
Polyuria & polydipsia (nephrogenic DI)

162
Q

What screening test would you order in a patient with hypokalaemia and hypertension?

A

Aldosterone: Renin ratio

163
Q

How would you manage a patient with a serum potassium 3.0-3.5 mmol/L?

A
  • Oral potassium chloride (two SandoK tablets tds for 48 hrs)
  • Recheck serum potassium
  • Treat the underlying cause e.g. spironolactone
164
Q

How would you manage a patient with a serum potassium < 3.0 mmol/L?

A
  • IV potassium chloride
  • Maximum rate 10 mmol per hour
  • Rates > 20 mmol per hour are highly irritating to peripheral veins
  • Treat the underlying cause e.g. spironolactone
165
Q

What is a normal WBC ?

A

4.0-11.0

166
Q

What is a normal platelet count?

A

150-400

167
Q

What is a normal serum Na concentration?

A

135-145

168
Q

What is a normal serum urea concentration?

A

3.5-7.0

169
Q

What is a normal serum creatinine concentration?

A

70-120

170
Q

What hormones are produced by the anterior pituitary?

A

GH, prolactin, TSH, LH, FSH, ACTH, MSH

171
Q

How can the function of the anterior pituitary be tested?

A

Combined pituitary function test aka triple test - inject insulin, GnRH and TRH, causing hypoglycaemia (<2.2). Measure hormones and cortisol.

172
Q

Does pituitary failure cause hypotension?

A

No!

173
Q

How is prolactin secretion controlled in the pituitary?

A

Dopamine inhibits prolactin secretion, whereas TRH stimulates prolactin secretion as well as stimulating TSH secretion, hence hypothyroidism can also cause secondary hyperprolactinaemia

174
Q

What level of prolactin is indicative of a prolactinoma?

A

> 6000

175
Q

In panhypopituitarism/pituitary failure, what hormone needs urgent replacement?

A

Hydrocortisone replacement.

Additionally/later Thyroxine, Oestrogen and GH replacement and a dopamine agonist: bromocriptine or cabergoline

176
Q

In addition to Hydrocortisone, Thyroxine, Oestrogen and GH replacement, what does a patient with a non-functioning pituitary adenoma need?

A

A dopamine agonist: bromocriptine or cabergoline. Wonā€™t shrink the tumour like it would with a prolactinoma but will reduce prolactin levels

177
Q

What dynamic test should be done for a patient with suspected acromegaly?

A

Glucose tolerance test

Also can measure IGF-1 levels

178
Q

What is the best treatment for acromegaly?

A

Pituitary surgery, followed by;
Pituitary radiotherapy,
Cabergoline,
Octreotide.

179
Q

What is the normal range of total serum Ca?

A

2.2-2.6 mmol/L

180
Q

How does PTH increase serum Ca concentration?

A

Increases bone resorption, renal resorption and gut absorption.

181
Q

How do vit D and PTH effect phosphate?

A

PTH stimulates renal phosphate wasting,

Vit D stimulates intestinal phosphate absorption

182
Q

What is the commonest cause of hypercalcaemia in the general population?

A

Primary hyperparathyroidism. In hospital it is malignancy.

183
Q

What is the defect in familial hypocalciuric/benign hypercalcaemia? How can it be distinquishes from primary hyperparathyroidism?

A

Calcium sensing receptor (CaSR)

Low urine calcium compared to high in primary hyperparathyroidism.

184
Q

What types of hypercalcaemia are there in malignancy?

A
  • Humoral hypercalcaemia of malignancy (eg small cell lung Ca) PTHrP
  • Bone metastases (eg breast Ca): Local bone osteolysis
  • Haematological malignancy (eg myeloma): cytokines
185
Q

What are the causes of non-PTH driven hypercalcaemia?

A
  • Malignancy
  • Sarcoidosis (non-renal 1Ī± hydroxylation)
  • Thyrotoxicosis (thyroxine -> bone resorption)
  • Hypoadrenalism (renal Ca2+ transport)
  • Thiazide diuretics (renal Ca2+ transport)
  • Excess vitamin D (eg sunbedsā€¦)
186
Q

What is the acute management for hypercalcaemia?

A

Fluid resuscitation
Bisphosphonates
Treat underlying cause

187
Q

What are the clinical signs of hypocalcaemia?

A 
Trousseau's sign
Chvostek's sign
Hyperreflexia
Laryngeal spasm (stidor)
Convulsions
Prolonged Q-T interval
Choked disk on fundoscopy
188
Q

What are the non-PTH driven causes of hypocalcaemia?

A

i. e. secondary hyperparathyroidism
- Vit D def
- Chronic kidney disease disease (1Ī± hydroxylation)
- PTH resistance (pseudohypoparathyroidism)

189
Q

What are the PTH driven causes of hypocalcaemia?

A

i. e. lack of PTH
- Surgical (inc post thyroidectomy)
- Auto-immune hypoparathyroidism
- Congenital absence of parathyroids (e.g. DiGeorge syndrome)
- Mg deficiency (PTH regulation)

190
Q 
A 48 year old woman presents with confusion, back pain and leg weakness.
Adj Ca 3.4 (2.2-2.6)
Phos 1.2 (0.8-1.5)
PTH 0.3 (1.1-6.8)
ALP 400 (30-130)
Diagnosis?
A

Metastatic disease, likely breast. Could be multiple myeloma but usually has a normal ALP and patient is too young.

191
Q 
A 55 year old man presents with muscle and bone aches. On DEXA scanning he is found to have reduced bone density.
Adj Ca 2.9 (2.2-2.6)
Phos 0.6 (0.8-1.5)
PTH 5.8 (1.1-6.8)
ALP 150 (30-130)
Vit D 55 (70-150)
Diagnosis?
A

Primary hyperparathyroidism, with vit D deficiency. Inappropriately normal PTH with reduced bone density.

192
Q

A 34 year old woman with a history of thyroid carcinoma presents with muscle weakness and paraesthesiae.
Adj Ca 1.6 (2.2-2.6)
Phos 1.4 (0.8-1.5)
PTH

A

Parathyroidectomy

193
Q

What abnormalities in biochemistry are there with osteoporosis?

A

None, normally normal.

194
Q

How is osteopenia defined with DEXA scans?

A

T score between -1 and -2.5

195
Q

What lifestyle modifications can be made to treat osteoporosis?

A

Encourage weight-bearing exercise
Stop smoking
Reduce alcohol intake

196
Q

What types of drugs are used to treat osteoporosis?

A 
Bisphosphonates
Vit D / Ca supplementation
Strontium
SERMs e.g. raloxifene
PTH analogue e.g. teriparatide
HRT - oestrogen
197
Q

What does vitamin D deficiency cause in adults?

A

Osteomalacia

Children get rickets

198
Q

What malignancy is there an increased risk of with Pagetā€™s disease?

A

Osteosarcoma

199
Q

Risk factors for renal stones?

A

Dehydration
Abnormal urine pH e.g. meat intake (alkolotic), renal tubular acidosis (acidic)
increased excretion of stone constituents
UTI
Anatomical variants

200
Q

What are the commonest compositions of renal calculi?

A 
Calcium - mixed (45%)
Calcium oxalate (35%)
Struvite (10%)
Uric acid (5%)
Cysteine (1-2%)
Calcium phosphate (1%)
201
Q

Which type of renal calculi are radio-lucent?

A

Uric acid and cysteine

202
Q

What composition is a ā€˜staghornā€™ calculi usually?

A

Struvite (triple phosphate)

203
Q

What is the Ca level in most patients with renal stones?

A

Normal

204
Q

Management of calcium renal stones

A 
Avoid dehydration
Reduce oxalate intake
Donā€™t reduce Ca intake (-> bone resorption + increased oxalate excretion)
Thiazides -> hypocalciuric
Citrate (alkalinise urine)
Treat underlying cause
205
Q

What is a common cause of struvite renal stones?

A

Urine infection with urea splitting organism e.g. Klebsiella, proteus etc)

206
Q

What causes cystine stones?

A

Underlying genetic defect causing cystinuria - often young patient.

207
Q

What are the three most common causes of hypothyroidism?

A
  • Hashimotoā€™s disease
  • Atrophic
  • Post-gravesā€™ disease treatment
208
Q

How can hypothyroidism affect Na+ and RBC levels?

A

Can cause hyponatraemia and a normocytic anaemia or macrocytic if have pernicious anaemia.

209
Q

Which antibodies may be associated with hypothyroidism?

A

Anti-Thyroid peroxidase (thyroid microsomal)

210
Q

What are the most common autoimmune conditions which may be associated with thyroid disease?

A

Pernicious anaemia
Coeliac disease
Addisonā€™s disease

211
Q

What test must be done before starting a patient on thyroxine?

A

E.C.G. to try and identify heart disease.

Start with low dose and titrate up.

212
Q

What are the side effects of excessive T4 replacement?

A

Osteopaenia

Atrial fibrillation

213
Q

How is subclinical hypothyroidism diagnosed?

A

High TSH but normal T4 - compensated hypothyroidism.
Test for anti-TPO antibodies to predict progression.
Associated with hypercholestrolaemia, only treat if raised.

214
Q

What happens to the free T4 level in pregnancy?

A

It increases in response to hCG, TSH goes down, TBG increases lots.

215
Q

What is sick euthyroid syndrome?

A

In response to any severe illness, the pituitary thyroid axis in altered to reduce T4 levels with a normal TSH. No clinical features of hypothyroidism.

216
Q

What are the three most common causes of hyperthyroidism?

A

Gravesā€™ disease 40-60%
Toxic multinodular goitre 30-50%
Single toxic adenoma 5%
Will have high update on technitium scan

217
Q

What causes of hyperthyroidism will have a low uptake on technitium scan?

A

Subacute thyroiditis

Postpartum thyroiditis

218
Q

What are the treatment options for gravesā€™ disease?

A

Radioactive Iodine 131 (not if eye disease)
Carbimazole
Propylthiouracil
- Titrate or block and replace

219
Q

What types of thyroid cancer are there?

A

Papillary
Follicular
Medullary carcinoma (C cells) - can be part of MEN type II

220
Q

What can be used as a tumour marker to monitor recurrence of thyroid cancer?

A

Thyroglobulin

221
Q

What tumour markers can be measured for medullary carcinoma of the thyroid?

A 
Calcitonin
Carcinoembryonic antigen (CEA)
222
Q

What are the fat soluble vitamins?

A

A retinol
D cholecaliferol
E Tocopherol
K Phytomenadione

223
Q

What problems can there be with vit A?

A

Deficiency - colour blindness

Excess - Exfoliation, Hepatitis

224
Q

What problems can there be with vit D?

A

Deficiency - Osteomalacia / Rickets

Excess - Hypercalcaemia

225
Q

What problems can there be with vit E?

A

Deficiency - Anaemia / neuropathy / malignancy / IHD

226
Q

What problems can a deficiency in B1 cause and how is it tested?

A

Thiamin deficiency can cause Beri-Beri, Neuropathy, Wernicke Syndrome.
Test RBC transketolase

227
Q

What problems can a deficiency in B2 cause and how is it tested?

A

Riboflavin deficiency can cause glossitis.

Test RBC glutathione reductase

228
Q

What problems can a deficiency or excess of B6 cause and how is it tested?

A

Pyridoxine deficiency can causes dermatitis, anaemia. Excess - neuropathy
Test RBC AST activation

229
Q

What problems can a deficiency in B12 cause and how is it tested?

A

Cobalamin deficiency can cause pernicious anaemia

Test serum B12 levels

230
Q

What problems can a deficiency or excess of Vit C cause and how is it tested?

A

Deficiency - scurvy
Excess - renal stones
Test - plasma levels

231
Q

What problems can a deficiency in folate cause and how is it tested?

A

Megaloblastic anaemia, Neural tube defects

Test - RBC folate

232
Q

What problems can a deficiency in B3 cause?

A

Niacin deficiency can cause Pellagra - Diarrhoea, Dementia, Dermatitis.

233
Q

What can be caused by a deficiency in zinc, copper or fluoride?

A

Zinc - dermatitis
Copper - anaemia
Fluoride - dental caries

234
Q

What main hormones are produced by white adipose tissue?

A

Leptin

Adiponectin (low levels linked to insulin resistance)

235
Q

What is the recommended protein intake per day for men and women?

A

Men 84 gm

Women 64 gm

236
Q

What types of fatty acids are better for you?

A

Polyunsaturated better than saturated

Cis-monosaturates better than trans-monosaturates

237
Q

What are the characteristics of metabolic syndrome?

A
  • Fasting glucose >6.0 mmol/L
  • HDL Men 135/80
  • Waist circumference men >102 women >88
  • Microalbumin, insulin resistance
238
Q

What endocrine disorders should be excluded with an obese patient?

A

Cushings and acromegaly

239
Q

What is the normal range of blood pH?

A

7.45 - 7.35

240
Q

What is the main buffer system present in different regions of the body?

A

Bicarbonate - ECF + glomerular filtrate
Haemoglobin - RBCs
Phosphate - renal tubular fluid + intracelluar
Also protein and bone

241
Q

What are the main causes of a metabolic acidosis?

A
  • increased H+ production e.g. diabetic ketoacidosis, lactic acidosis
  • decreased H+ excretion e.g. renal failure
  • loss of bicarbonate e.g. fistula
242
Q

What are the different plasma lipoproteins, in size order?

A

Largest: Chylomicrons
VLDL - main triglyceride carrier ~55%
LDL - main cholesterol carrier ~70%
Smallest: HCL

243
Q

What mutations can cause familial hypercholesterolaemia (type II)?

A

Dominant mutations of LDL receptor, apoB or PCSK9 genes.

Rarely, autosomal recessive mutation of LDLRAP1

244
Q

What are the mutations in phytosterolaemia?

A

mutations of ATP-binding cassette (ABC) transporters G5 and G8 - allow gut to absorb plant sterols

245
Q

What are the commonest causes of primary hypercholesterolaemia ?

A
  • Familial hypercholesterolaemia
  • Polygenic hypercholesterolaemia
  • Familial hyper-alpha-lipoproteinaemia
  • Phytosterolaemia
  • cholesterol ester storage disease
  • cerebro-tendinous xanthomatosis
246
Q

What are the different types of familial hyperlipidemias and what mutations are associated with them?

A

Type I - lipoprotein lipase or apoC II
Type II aka Familial hypercholesterolemia - LDLR, apoB, PCSK9
Type III - apoE2
Type IV aka Familial hypertriglyceridemia
Type V - ?

247
Q

What is pathognomonic of familial hyperlipidemia type III?

A

Palmar striae - yellow/xanthomatous palmar crease.

248
Q

What are the causes of secondary hyperlipidaemia?

A

Hormonal influences: pregnancy, exogenous sex hormones or hypothyroidism
Metabolic disorders: diabetes and obesity
Renal dysfunction
Obstructive liver disease
Beverages: alcohol and coffee
Iatrogenic: cyclosporin, amiodarone, retinoids and anti-retroviral drugs

249
Q

What are the causes of primary hypolipoproteinaemia?

A
  • A-beta-lipoproteinaemia: recessively inherited mutations of microsomal triglyceride transport protein (MTP);
  • Familial hypo-beta-lipoproteinaemia: dominantly inherited mutations of the apoB gene;
  • Tangier disease (HDL def): homozygosity for mutations of ABCA1;
  • Familial hypoalphalipoproteinaemia, heterozygous inheritance of mutations of either ABCA1 or of apoA-1.
250
Q

What is the best biochemical predictor of CHD risk?

A

Total:HDL cholesterol ratio, which reflects the opposing influences of atherogenic VLDL and LDL versus anti-atherogenic HDL.

251
Q

What lipid-lowering drugs are there?

A

HMG CoA reductase inhibitor (statins)
Bile acid sequestrants (eg colestryramine)
In deveopment: MTP-inhibitors, anti-sense apoB oligonucleotides and anti-PCSK9 monoclonal antibodies.

252
Q

What treatment is used to treat severe, statin-refractory forms of dyslipidaemia?

A

Lipoprotein apheresis

253
Q

How is a successful outcome from bariatric surgery defined?

A

> 50% loss in excess body weight (actual ā€“ ideal) and accompanied by marked decreases in diabetes, serum triglycerides, fatty liver and hypertension.

254
Q

What drugs are used to raise HDL levels?

A

CETP inhibitors and apoA1 and HDL-mimetic compounds.

255
Q

What is uric acid?

A

The end product of purine metabolism.

256
Q

How is urate excreted?

A

1/3 secreted into the gut - degraded by bacterial uricase

2/3 renal excretion - 90% reabsorbed in PCT

257
Q

What are the primary causes of urate overproduction?

A

PRPS overactivity (denovo synthesis) or HGPRT deficiency (salvage pathway)

258
Q

What are the secondary causes of urate overproduction?

A
  • increased dietary purine intake
  • increased nucleotide turnover (psoriasis, myeolo- or lymphoproliferative diseases)
  • increased ATP metabolism
  • drugs e.g. cytotoxics
259
Q

What are the causes of urate under-excretion?

A
  • Primary hyperuricaemia - defect in PCT transporters (increased resorption)
  • Impaired renal function
  • Inhibition of urate secretion (acidosis)
  • Drugs
260
Q

What are the effects of high uric acid?

A
  • Gout
  • Renal calculi
  • Tophi
  • Acute urate nephropathy - widespread crystallisation in renal tubules
261
Q

What crystals precipitate from high uric acid and at what level?

A

Monosodium urate crystals

[urate] > 0.38 mmol/L

262
Q

What is acute and chronic gout called?

A

Podagra - big toe

Tophaceous gout - chronic

263
Q

What are the risk factors for gout?

A 
Hyperuricaemia
Family history
Obesity
Alcohol
Hypertension
Renal impairment
Drugs (diuretics, salicylates (low dose), tacrolimus, ciclosporin, cytotoxics)
264
Q

What is the treatment for an acute gout attack?

A

NSAIDs
Colchicine
Glucocoticoids

265
Q

For which patients is urate lowering therapy indicated and with what treatment?

A

Patients with recurrent gout attacks, chronic arthropathy, tophi and gout with uric acid stones.
Allopurinol reduces synthesis
Probenecid increases renal excretion

266
Q

How does allopurinol work?

A

Xanthene oxidase inhibitor - blocks uric acid production

267
Q

What do gout and pseudogout crystals look like under polarised light?

A

Monosodium urate - yellow, negatively birefringent

Calcium pyrophosphate - blue, positively birefringent

268
Q

What is Lesch Nyhan syndrome?

A

X-linked deficiency of hypoxanthine-guanine phosphoribosyltransferase (HGPRT - salvage pathway)

  • normal at birth, dev delay 6/12
  • hyperuricaemia
  • choreiform movements (1 yr)
  • spasticity, mental retardation, self mutilation (85%)
269
Q

Which tissues make alkaline phosphatase?

A

Bone, liver, intestines, placenta.

270
Q

How can the source of increased serum enzymes be localised to specific tissues?

A

1 - measurement of more than one enzyme e.g. GGT can be used to localise ALP to liver
2 - Separation and measurement of tissue- specific isoenzymes e.g. bone and liver ALP

271
Q

What pathological causes are there for a raised ALP?

A

> 5x Upper limit of normal
- Bone ( Pagets, Osteomalacia)
- Liver ( cholestasis, cirrhosis)
< 5x Upper Limit Normal
- Bone ( tumours, fractures, osteomyelitis)
- Liver (infiltrative disease,hepatitis)
NOT osteoporosis unless complicated by fractures

272
Q

What forms of creatine kinase are there?

A

CK-MM- skeletal muscles
CK-MB (1 & 2) ā€“ cardiac muscles
CK-BB ā€“ brain ā€“ activity minimal even in severe brain damage

273
Q

What is the time line for troponin following a MI? When should it be measured clinically?

A

Rise 4-6 hours post MI, peak at 12-24 hours, remains elevated for 3-10 days.
Measure at 6 and 12 hrs post onset of chest pain.

274
Q

What biomarkers can be measured in heart failure?

A

Atrial and brain natriuretic peptides (secreted by atria and ventricles, respectively)
BNP can be measured to assess ventricular function - if normal, unlikely to have heart failure, used to exclude.

275
Q

Define 1 international unit (U) of enzyme activity.

A
  • 1 International Unit (U) of enzyme activity is defined as the quantity of enzyme that catalyses the reaction of one Ī¼mol of substrate per minute.
  • Activity of an enzyme is dependent on assay conditions such as temperature, pH.
276
Q

What is the action of ADH (vasopresin)?

A
  • Acts of V2 receptors on renal tubular cells in collecting duct resulting in aquaporin-2 water channels being inserted into the tubular membrane - increases water resorption.
  • At high conc binds to V1 receptors on vascular smooth muscle causing vasoconstriction
277
Q

What are the two main stimuli for ADH secretion?

A
  • Serum osmolality (mediated by hypothalamic osmoreceptors)

- Blood volume/pressure (mediated by baroreceptors in carotids, atria, aorta)

278
Q

What are the causes of hyponatraemia in a hypovolaemic patient?

A
  • Renal cause of volume depletion e.g. diuretics, salt-losing nephropathy
  • Extra-renal cause of volume depletion e.g. diarrhoea, vomiting
279
Q

What are the causes of hyponatraemia in a hypervolaemic patient?

A
  • Cardiac failure
  • Cirrhosis
  • Renal failure
280
Q

What are the causes of hyponatraemia in a euvolaemic patient?

A
  • Hypothyroidism
  • Adrenal insufficiency
  • Syndrome of inappropriate ADH (SIADH)
281
Q

What are the causes of Syndrome of Inappropriate ADH secretion (SIADH)?

A
  • CNS pathology
  • Lung pathology
  • Drugs (SSRI, TCA, opiates, PPIs, carbamazepine)
  • Tumours
282
Q

What investigations would you order in a patient with euvolaemic hyponatraemia?

A

? Hypothyroidism: Thyroid function tests
? Adrenal insufficiency: Short Synacthen test
? SIADH: Plasma & urine osmolality (low plasma & high urine osmolality)

283
Q

How would you manage a hypovolaemic patient with hyponatraemia?

A

Volume replacement with 0.9% saline

284
Q

How would you manage a hypervolaemic patient with hyponatraemia?

A 
Fluid restriction (total fluid <500ml)
Treat the underlying cause
285
Q

How would you manage a euvolaemic patient with hyponatraemia?

A 
Fluid restriction (total fluid <500ml)
Treat the underlying cause
286
Q

What is the most important point to remember while correcting hyponatraemia?

A
  • Serum Na must NOT be corrected > 10 mmol/L in the first 24 hours
  • Risk of osmotic demyelination: central pontine myelionlysis (quadriplegia, pseudobulbar palsy, seizures, coma, death)
287
Q

If water restriction is insufficient to treat SIADH, what drugs can be used?

A
  • Demeclocycline: Reduces responsiveness of collecting tubule cells to ADH. Monitor U&Es (risk of nephrotoxicity)
  • Tolvaptan: V2 receptor antagonist
288
Q

What are the main causes of hypernatraemia?

A
  • Unreplaced water loss:
    Gastrointestinal losses
    Renal losses: osmotic diuresis, reduced ADH release/action (Diabetes insipidus)
  • Patient cannot control water intake e.g. children, elderly
289
Q

What investigations would you order in a patient with suspected diabetes insipidus?

A

Water deprivation test

290
Q

How would you treat hypernatraemia?

A

Fluid replacement
- Correct water deficit (5% dextrose)
- Correct volume depletion (0.9% saline)
Treat the underlying cause

291
Q

How do neonatal kidneys differ to adult ones?

A

1 - Neonatal GFR is low
2 - Proximal tubules are short and less convoluted
3 - The distal tubules are relatively unresponsive to aldosterone
4 - The loops of Henle/distal collecting ducts are short
5 - Renal function does not fully mature until ~2 years

292
Q

What are the consequences of a low GFR in neonates?

A

Slow excretion of a solute load

Limited amount of Na+ available for H+ exchange - suseptible to acidosis

293
Q

What are the consequences of short and less convoluted proximal tubules in neonates?

A

There is a lower reabsorptove capability but it is usually adequate for the small filtered load.
Threshold for glycosuria lower

294
Q

What are the consequences of short loops of Henle/distal collecting ducts in neonates?

A

They have a reduced concentrating ability with a maximum urine osmolality of 700 mmol/kg

295
Q

What are the consequences of distal tubule unresponsiveness to aldosterone in neonates?

A

Leads to a persistent loss of Na and hence a reduced potential potassium excretion: higher ULN 6.0 mmol/L

296
Q

What are the commonest causes of a conjugated hyperbilirubinaemia in neonates?

A
  • Biliary atresia
  • Choledocal cyst
  • Ascending cholangitis: associated with lipid content of TPN
  • Inherited metabolic diseases (Alpha-1-antitrypsin deficiency, Tyrosinaemia type I,Galactosaemias, Peroxisomal disorders)
297
Q

What are the causes of a unconjugated hyperbilirubinaemia in neonates?

A 
Haemolytic
- Haemolytic disease (ABO, rhesus etc)
- G-6-PD deficiency
Non-haemolytic
- Feeding problems 
- Breast milk jaundice
- Prenatal infection/sepsis, hepatitis
- Hypothyroidism
- Crigler-Najjar type I

Pathology (5 decks)

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