Week 8: Renal disease (1) (renal function tests and electrolyte balance)

Question 1

renal function tests

Answer 1

bloods

urine

imaging

Question 2

blood tests

Answer 2

• FBC – Anaemia, infection, allergic reactions,
• Haematinics – Iron/Folate/B12 deficiency
• U&Es – Potassium, Urea, Creatinine, Bicarbonate
• Bone profile – Calcium, Phosphate, PTH, Alkaline Phosphatase
• CRP – Infection/Inflammation
• HbA1c – Diabetic control
• ABG/VBG

Question 3

urine

Answer 3

• Urine Dipstick – Infection (leukocytes, nitrites); Glomerular pathology (blood, protein)
• Urine Protein: Creatinine Ratio – Quantifies the amount of all protein in the urine
• Urine Albumin:Creatinine Ratio – Quantifies just albumin (good for diagnosing and monitoring diabetic nephropathy)
• Urine microscopy, culture and sensitivity

Question 4

imaging

Answer 4

US KUB (kidneys, ureters and bladder)

• look for peri-nephric collections
• size of kidneys
• corticomedullary differentiation
• hydronephrosis

Question 5

ABG results

Answer 5

Question 6

the anion gap

Answer 6

useful in working out what could be causing acidosis

Question 7

high anion gap

Answer 7

acidosis due to increased acid

Question 8

normal anion gap

Answer 8

acidosis due tor educed alkali

Question 9

Diabetes insipidus

Answer 9

Differential- psychogenic polydipsia (mental illness and developmental disability)

Presentation

• Dilute urine (osmolality <300)
• Polydipsia and polyuria
• Impaired release of ADH (cranial DI)

Causes

• Impaired release:Cranial DI
  
  • Trauma/post op tumours
  • Cerebral sarcoid/TB infections (menin/encep)
  • Cerebral vasculitis (SLE/Wegeners)
• Resistance to ADH: Nephrogenic DI
  
  • Congenital, drugs (lithium, amphotericin, demeclocycline), hypokalaemia, hypercalcaemia, tubulointerstitial disease

Treatment: generally- free water

Question 10

types of hypernatremia

Answer 10

• Hypovolaemic high Na
  
  • Renal free water losses (osmotic diuresis(NG feed etc), loop diuretics, intrinsic renal disease)
• Euvolemic High Na
  
  • Renal losses (diabetes insipidus, hypodipsia - dehydration)
• Hypervolaemia High Na (sodium Gains)
  
  • Primary hyperaldosteronism, Cushing’s syndrome, hypertonic dialysis, hypertonic sodium bicarbonate, sodium chloride tablets

Question 11

hypernatraemia impact on body

Answer 11

• Causes cellular dehydration (osmotic drag)
• Creates vascular shear stress (bleeding and thrombosis)

Question 12

presentations of hypernatremia

Answer 12

• Thirst
• Apathy
• Irritability
• Weakness
• Confusion
• Reduced consciousness
• Seizures
• Hyperreflexia
• Spasticity
• Coma

Question 13

Change in sodium is rarely a change in sodium conc, usually a change in

Answer 13

water

Question 14

causes of hypernatraemia

Answer 14

• Think of water- less water to sodium (not really about sodium)
• Causes
  
  • Osmotic diuresis (e.g. uncontrolled diabetes)- excreting too much water
  • Fluid loss without replacement (sweating, burns, vomiting)
  • Diabetes insipidus (suspect of lots of dilute urine produced)
  • Incorrect intravenous fluid replacement
  • Primary aldosteronism

Question 15

hyponatraemia impact on the body

Answer 15

causes cellular swelling

Question 16

symptoms of hyponatraemia

Answer 16

• Decreases perception
• Gait disturbance
• Yawning
• Nausea
• Reversible ataxia
• Headache
• Apathy
• Confusion
• Seizures
• Coma

Question 17

causes of hyponatreamia

Answer 17

• Pseudohyponatremia
  
  • High lipids
  • Myeloma
  • Hyperglycaemia
  • Uraemia
• Hypovolaemic hyponatremia
• Euvolemic hyponatremia
• SIADH
• Hypervolemic hyponatremia

Question 18

causes of hyponatraemia

Answer 18

• Pseudohyponatremia
  
  • High lipids
  • Myeloma
  • Hyperglycaemia
  • Uraemia
• Hypovolaemic hyponatremia
• Euvolemic hyponatremia
• SIADH
• Hypervolemic hyponatremia

Question 19

investigations for hyponatraemia

Answer 19

• Plasma osmolality (if normal or raised then pseudohyponatremia)
• Hypokalaemia/hypomagnesemia potentiates ADH release
• Urine sodium (if <20 then non-renal salt losses, if >40 then SiADH) (diuretics may confound)
• TSH
• 9am cortisol
• Calcium
• Albumin
• Glucose
• LFT
• CT head
• CT chest- SIADH

Question 20

Risk of correcting hyponatraemia quickly

Answer 20

Too rapid correction of chronic hyponatraemia leads to central pontine/osmotic myelinosis.

• Aim to correct <12 mmol/L/day

Question 21

treatment of hyponatraemia

Answer 21

• Acute (tends to be iatrogenic, polydipsia, colonoscopy prep, ecstasy)
  
  • If acute hyponatraemia (within 48 hours) and symptomatic – Give 3% hypertonic saline IV boluses +/- Furosemide Chronic
• If chronic (>48 hours) and symptomatic – hypertonic saline boluses if having seizures.
• Otherwise isotonic saline and furosemide – aim to correct 8mmol/L in 24 hours
• If chronic and asymptomatic – water restriction, stop offending drug, if dehydrated – restore volume, if overloaded – Na and water restriction and diuretics

Question 22

causes of euvolemic hyponatraemia

Answer 22

normal sodium stores and a total body excess of free water

causes:

• Hypothyroidism
• Primary polydipsia (if urine osmolality <200)
• Glucocorticoid deficiency- adrenal insufficiency
• SIADH

Question 23

SIADH

Answer 23

• Low serum osmolality
• Inappropriately concentrated urine – Urine osmolality >100
• Urine Na >20
• Clinical euvolaemia
• Not on diuretics
• Diagnosis of elimination – normal renal, thyroid, adrenal function

Question 24

Management of SIADH

Answer 24

• Fluid restrict <800ml/day.
• PO sodium chloride
• May give furosemide
• Demeclocycline induces diabetes insipidus (reversing ADH effect), alternatively Tolvaptan

Question 25

causes of hypovolaemic hyponatraemia

Answer 25

• Renal loss (urine Na+ >20 mmol/L)
  
  • Diuretics (thiazides), osmotic diuresis (glucose, urea in recovering ATN), Addison’s disease (mineralocorticoid deficiency)
• Non renal loss (urine Na <20mmol/L)
  
  • Diarrhoea, vomiting, sweating, third space losses (burns, bowel obstruction, pancreatitis)

Question 26

treatment of hypovolaemic hyponatraemia

Answer 26

• IV fluids (0.9% NaCl at 1-3ml/kg/hour
• Give K if necessary

Question 27

hypervolemic hyponatraemia

Answer 27

This increase in total body water is greater than the total body sodium level, resulting in edema.

Causes

• CCF
• Nephrotic syndrome
• Liver cirrhosis

Treatment

• Fluid restriction and consider furosemide

Question 28

cause sof hyperkalaemia

Answer 28

• CKD, K rich diet with CKD (dried fruit, potatoes, oranges, tomatoes, avocados, nuts)
• Drugs (ACEi/ARBs/Spironolactone/Amiloride/NSAIDs/ Heparin/ LMWH/Cyclosporin or calcineurin inhibitors/High dose Trimethoprim/ Digoxin toxicity/B- blockers)
• Hypoaldosteronism (T4RTA), Addison’s disease, Acidosis, DKA (insulin deficiency), Rhabdomyolysis, tumour lysis, Massive haemolysis, Succinylcholine use
• Rarer – Hyperkaliaemic periodic paralysis, Gordon’s syndrome
• Artifact Hyperkalaemia – haemolysis, leucocytosis, thrombocytosis

Question 29

ECG changes in hyperkalaemia

Answer 29

• Tented T waves
• Prolonged QRS
• Slurring of ST segment
• Loss of P waves
• Asystole

Question 30

treatment of hyperkalaemia

Answer 30

• 10mls of 10% calcium gluconate over 5-10 minutes
  
  • Stabilises myocardium to prevent arrhythmias
• IV fast acting insulin (actrapid)
  
  • With 10 units IV glucose/dextrose 50% 50mls
  • Shifting potassium back into the intracellular space
• Calcium resonium
  
  • 15-45g orally or rectally
  • Eliminating potassium from body
• Furosemide
  
  • Eliminating potassium from the body
• Dialysis
  
  • Eliminating potassium from the body

Question 31

Hyporeninaemic hypoaldosteronism (Type IV renal tubular acidosis)

Answer 31

• Hypochloraemic acidosis in about 50%
• hyperkalaemia
• Often hypertensive with increased extra-cellular fluid volume (renin often down regulated by fluid overload

Risk factors

• Increased age
• Reduced eGFR
• Diabetes nephropathy
• Nephritis
• TIN/sickle cells
• NSAIDs CNI
• Lupus nephritis

Question 32

symptoms of hypokalaemia

Answer 32

• Fatigue
• Constipation
• Proximal muscle weakness
• Paralysis
• Cardiac arrhythmias
• Worsened glucose control in diabetics
• Hypertension

Question 33

ECG treatment in hypokalaemia

Answer 33

• Small T waves
• U wave (after T)
• Increased PR interval

Question 34

causes of hypokalaemia

Answer 34

• Pseudohypokalaemia – acute leukaemia
• Extra-renal losses - Inadequate PO intake, Gut losses (vomiting, NG losses, secretory Diarrhoea, laxatives, VIPoma, Zollinger-Ellison, Ileostomy, enteric fistula)
• Redistribution – Delirium tremens, beta agonists, insulin, caffeine, theophylline, alpha-blockers (Doxazosin), hypokalaemic periodic paralysis (inherited or acquired from thyrotoxicosis – Asian males)
• Refeeding syndrome, alkalosis, vigorous exercise, glue-sniffing (Toluene can cause Fanconi/RTA II with renal potassium wasting)
• Primary hyperaldosteronism (conn’s syndrome) Cushing’s syndrome, Secondary hyperaldosteronism (liver failure, heart failure, nephritic syndrome),
• Renal losses (diuretics, RTA, Tubulopathies - Bartters/Liddles/Gittelmans), liquorice, glucocorticoids, hypomagnesaemia.

Question 35

treatment of hypokalaemia

Answer 35

• Replace magnesium
• Oral K replacement
• IV K replacement (Usually in 0.9% NaCl - avoid in dextrose as induces further hypokalaemia)