KidneyFish
Nephromaths
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Disclaimer
Acknowledgements
I Introduction
1
Introduction
1.1
Work in progress
1.2
What this book is - and what it is not
1.3
How to use this book
2
Basic Concepts
2.1
Validity & assumptions
2.2
General principles
2.2.1
Balance
2.2.2
Testing during stress & “normal ranges”
2.2.3
Renal clearance & fractional excretion
2.2.4
Tmax
2.2.5
Osmolarity, osmolality & tonicity
2.2.6
Gaps
3
General approach to a patient with electrolyte disturbance
3.1
Vomiting & diarrhoea
3.1.1
Electrolyte content of GI fluids
3.1.2
Vomiting
3.1.3
Quantitative assessment after vomiting
3.1.4
Diarrhoea
3.2
Drugs
3.3
IV fluids & electrolyte supplements
3.4
Diet
3.5
Basic set of investigations
II Acid-base
4
Acid-base & chloride
4.1
Acid-base homeostasis
4.2
pH
4.3
Adaptation
4.4
Renal control of acid-base homeostasis
4.4.1
Normal renal response to chronic acidosis
4.4.2
Renal response to alkalosis
5
Metabolic acidosis
5.1
Serum anion & osmolar gaps
5.2
Investigations in HCMA
5.2.1
Urine pH
5.2.2
Urine anion gap, osmolar gap, ammonium
5.3
Causes of a metabolic acidosis
5.3.1
Approach to metabolic acidosis
6
Metabolic alkalosis (& chloride homeostasis)
6.1
Causes of a metabolic alkalosis
6.2
Chloride
6.2.1
Chloride-depletion alkalosis
III Water and sodium
7
Water and sodium
7.1
Total body water
7.2
Plasma sodium
7.3
Renal water excretion
7.4
Urine osmolality
8
Hyponatraemia
8.1
Drug causes of hyponatraemia
8.2
Correction for hyperglycaemia
8.3
Urine sodium
8.3.1
FE
Na
8.3.2
FE
urate
as an alternative index of volume status
8.4
Free water clearance
8.4.1
Calculating free water clearance
8.4.2
Clinical utility of free water clearance
8.4.3
Urine flow rate in hyponatraemia
8.5
SIAD
8.5.1
Diagnosis
8.5.2
Subtypes
8.5.3
Treatment
9
Hypernatraemia
9.1
Causes of hypernatraemia
9.2
Diagnosis in hypernatraemia
9.3
Treatment of hypernatraemia
10
Polyuria
10.1
Causes
10.2
Investigation of polyuria
10.3
Uses for copeptin testing
10.3.1
Assay details
10.3.2
Polyuria-polydipsia (hypotonic polyuria)
10.3.3
Hypernatraemia
10.3.4
Hyponatraemia
IV Potassium
11
Potassium
11.1
Quantification
11.1.1
Interpretation
11.2
TTKG
Assumptions & pre-requisites
Interpretation
12
Hypokalaemia
12.1
Causes of hypokalaemia
12.2
Causes of K loss
12.3
Diagnostic approach
12.4
Vomiting
12.5
Non-reasbsorbable anions
12.6
Hypokalaemic periodic paralysis
13
Hyperkalaemia
13.1
Causes of hyperkalaemia
13.2
Causes of spurious hyper- and hypokalaemia
V Phosphate, Calcium, Magnesium
14
Phosphate
14.1
Urinary phosphate
14.1.1
General approach
14.1.2
Measuring urinary phosphate and calculating TmP/GFR
14.1.3
Reference ranges
14.2
Hypophosphataemia
14.2.1
Consequences
14.2.2
Causes of hypophosphataemia
14.2.3
Notes on specific causes
15
Calcium
15.1
Investigations in hypercalcaemia:
15.2
Urine calcium
15.3
Interpreting the results
15.3.1
Unit conversions
15.3.2
Normal calcium excretion:
15.3.3
Hypercalciuria (e.g. in hyperPTH, other causes of hypercalcaemia, RTA):
15.3.4
Hypocalciuria (e.g. FHH, Gitelman):
16
Magnesium
16.1
Mg homeostasis
16.2
Hypomagnesaemia
16.2.1
Consequences
16.2.2
Differential diagnosis of hypomagesaemia
16.2.3
Notes on specific causes
16.3
Investigations
VI Tubulopathies
17
Tubulopathies
17.1
Inherited
17.1.1
Notes on some of the inherited tubulopathies
17.2
Acquired
17.3
Tubulopathy syndromes
17.3.1
Interpretation of these electrolyte syndromes
17.4
Diagnostic approach in suspected tubulopathy
17.4.1
Fractional excretions
17.4.2
Specialised testing
17.5
Sjogren syndrome
17.6
Lithium-associated tubulopathy
17.6.1
Pathogenesis
17.6.2
Polyuria
17.6.3
TIN
17.6.4
Podocytopathy
17.7
Salt-wasting tubulopathies
18
Renal tubular acidosis
18.1
Classification of RTA
18.1.1
Pathogenesis of hypokalaemic RTA
18.1.2
Pathogenesis of hyperkalaemic RTA
18.1.3
Associations
18.1.4
Investigation of suspected RTA
18.1.5
Causes
18.2
Fanconi syndrome
Appendices
A
Appendix 1 - notation & abbreviations
A.1
Notation
A.2
Glossary of abbreviations
B
Appendix 2 - rules of thumb
B.1
pH and [H
+
]
B.2
Urine specific gravity and UOsm
C
Appendix 3 - what’s the mechanism?
C.1
Mechanisms in dRTA (see ESPN clinical practice points, NDT 2021):
D
Appendix 4 - references
Published with bookdown
Nephromaths
Nephromaths
Robert W Hunter
2025-01-10
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