1. U&Es Interpretation
Dr Dan Taylor FY1

2. Urea & Electrolytes Components
Creatinine
Sodium
Potassium
Calcium
Magnesium
Phosphate
Urea Cycle converts ammonia to urea in the liver
A less toxic metabolite
Transported to the kidneys where it is excreted

3. Urea & Electrolytes Components Urea Creatinine Sodium Potassium
Calcium
Magnesium
Phosphate
Creatine is produced by the liver and used as part of fast energy stores by binding to phosphate (phosphorylation)
Creatine phosphate then broken down to make ATP + creatinine waste product
Transported to the kidneys where it is excreted at a steady and constant rate
Creatinine concentration a specific marker of renal function but depends on muscle store

4. Urea & Electrolytes Components Main component of extra-cellular fluid
Creatinine
Sodium
Potassium
Calcium
Magnesium
Phosphate
Main component of extra-cellular fluid
Na content monitored by aortic/carotid bodies and as reflects fluid status by heart chamber stretch
Juxtaglomerular apparatus monitors Na and causes renin release

6. Urea & Electrolytes Components
Creatinine
Sodium
Potassium
Calcium
Magnesium
Phosphate
Main intracellular electrolyte component
Levels controlled by aldosterone at the DCT acting to increase K+ excretion
Levels also vary with H+ ion concentration as they compete for transporter in the kidney

7. Urea & Electrolytes Components
Creatinine
Sodium
Potassium
Calcium
Magnesium
Phosphate
Calcium and phosphate both closely related
Generally stored within bone
Levels controlled by PTH released from the parathyroid gland
PTH production affected by Mg2+ levels

9. Urea & Electrolytes Components
Creatinine
Sodium
Potassium
Calcium
Magnesium
Phosphate
Vital electrolyte used in bone/teeth formation but also nerve conduction and signalling
Mostly found intracellular

10. Doctor, can you please review the U&Es??
Urea 22.0 ( )
Creatinine 286 (45-100)
Na 142 ( )
K 5.6 ( )

11. Raised Creatinine Problems? Raised Urea Kidney damage
Dehydration
GI bleed (urea rise in isolation)
Increased protein breakdown (surgery, trauma, infection, malignancy)
High protein intake
Kidney damage
Raised Creatinine
Kidney damage
Increased lean body mass

12. Acute Kidney Injury (AKI)
Rise in creatinine >50% from baseline or urine output <0.5ml/kg/hr for 6+ hours
Investigations
Urine dipstick
Bloods – FBC, U&Es, CRP, chemistry profile, PTH
VBG – acidosis?/hyperkalaemia?
Fluid balance chart (catherterise patient)
Stop nephrotoxins
?renal screen (if indicated)
?renal tract ultrasound (if severe)

13. AKI Nephritic screen Pre-Renal (70%) ANA
Hypovolaemia, Dehydration, sepsis
Low BP, equal rise in urea and creat
IV fluid replacement
May be complicated by ATN
Nephritic screen
ANA
P-ANCA/c-ANCA
Anti-GBM
Complement screen
RhF
Hepatitis serology
Anti-phospholipid antibody
Renal ultrasound
Renal biopsy
Myeloma screen
FBC, chem/bone profile, LDH
Urinary bence-jones protein
Serum immunoglobulins
Serum electrophoresis and immunofixation
Skeletal survey
Creatine kinase
Intrinsic Renal (20%)
ATN (ischaemic/nephrotoxic), nephritis, glomerulonephritis
Causative drugs, hypovolaemic episodes, haematuria, proteinuria
Dipstick blood +++/protein +++
Urine Protein-creatinine ratio (PCR) to quantify and monitor protein loss
Renal screen
Treat the underlying cause and give bicarbonate if indicated (protects the kidney)
Post-Renal (10%)
Urinary tract obstruction (stones/prostate/tumour/stricture)
Renal tract ultrasound indicated
Relieve the obstruction (catherterise/nephrostomy)

14. Chronic Kidney Disease
Markers of damaged kidney function (proteinuria) or decreased eGFR for >3 months
Graded 1-5 based on eGFR
Causes
Diabetes and hypertension
Chronic glomerulonephritidies and inherited disorders/drugs
Management
Manage underlying cause
Fluid restriction/low protein intake/ACE-inhibitor
Treat complications
Anaemia, hypertension, oedema, renal bone disease, hyperkalaemia
Dialysis if eGFR<15/complications
Indications for Dialysis
Acidosis
Electrolyte abnormalities
Intoxication
Overload
Uraemia (symptomatic or >60.0)

15. Hypernatraemia (>155)
Reflects an inability to concentrate urine so more water is lost than salt
Concentrated serum
Causes
Fluid loss without replacement
Diarrhoea/vomiting
Burns
Decreased access to water
Incorrect IV fluids
Diabetes insipidus (no ADH)
Osmotic diuresis
Aldosterone increase
Conn’s
Cushings
Signs and Symptoms
Dehydration/thirst
lethargy/weakness
Confusion/coma
Seizures Ix
U&E
↑Na
↑urea/alb
Identify cause
Management
Increase oral water intake if dehydrated
IV fluids (dextrose and saline)
Correct use of IV fluids
Guide therapy by volume status and bloods

16. Hyponatraemia (<135)
Does not necessarily indicate a depletion – depends on fluid state
Suggestion of an issue with sodium distribution in water
Causes
Dehydrated
Actual fluid loss
Euvolaemic
Distribution problem
Oedematous
Dilution
Signs and Symptoms
Anorexia/nausea
Malaise/weakness
Confusion/coma
seizures Ix
U&E
Urine and serum osmolality
Urine sodium
Management
Fluid restriction
Corrects distribution and dilution
Replace fluids IV
Pharmacological
Demeclocycline or vaptans

17. Hyponatraemia Euvolaemic High urine osmolality (concentrated) SIADH
Low urine osmolality (dilute)
Water overload
Hypothyroidism
Addison's
Too much dextrose
Dehydrated
High urinary Na (renal loss)
Addison’s (low aldosterone)
Excess diuretic (thiazide/loop)
Non-functioning kidneys
Osmolar diuresis
Low urinary Na (loss elsewhere)
Diarrhoea
Vomiting
Burns/heat/sweating
Small bowel obstruction
Overloaded
Renal failure
Cardiac failure
Low protein states
Liver failure
Nephrotic syndrome

18. Hyperkalaemia (>6.5)
Emergency as may lead to myocardial excitability and ventricular fibrillation
Be aware of artefactual results: haemolysis, delayed analysis, contamination
Causes
Impaired renal excretion
K+ sparing diuretics
AKI/CKD
Hypoaldosteronism
Addison’s Disease
ACE-i/ARBs
Release from cells
Acidosis
Cell lysis/burns
Tumour lysis syndrome
Rhabdomyolysis
Signs and Symptoms
Fast irregular pulse
Palpitations
Chest pain
Light headedness Ix
U&E
ECG
Management
Check the patient and ECG – repeat
1.) 10mls 10% IV calcium gluconate
2.) 2.5mg salbutamol nebs
3.) Insulin + glucose (10u in 50ml 50% dextrose)
4.) dialysis/haemofiltration

19. Hypokalaemia (<2.5) Very common electrolyte abnormality
Related to Mg concentration if it is also low K+ will not correct
Causes
Diuretics (thiazide and loop)
Alkalosis
Vomiting and diarrhoea
Renal tubular damage
Cushing’s/steroids
Conns
Villous adenoma
Signs and Symptoms
Usually asymptomatic
Hypotonia/hyporeflexia
Palpitations Ix
U&E & Mg
ECG
Management
Oral replacement (sando K)
IV replacement – slowly & diluted

20. Hypercalcaemia (>2.6)
Calcium involved in cell signalling and muscle function
Adjusted calcium values in relation to albumin as calcium bound to albumin readily
Causes
1⁰ hyperparathyroidism
3⁰ hyperparathyroidism
Malignancy
Bony metastases
Myeloma
PTHrp
Vitamin D excess
Sarcoidosis
Signs and Symptoms
Bones, stones, groans & psychic moans
Bone pain & path #
Abdo pain/ n+v
Tiredness/weakness
Confusion/depression
Polydipsia/polyuria Ix
Ca and Po4
Raised together – malignancy
High Ca, low Po4 – PTH driven
Myeloma screen
Identify malignancy
Management
Correct dehydration aggressively
IV bisphosphonate

21. Hypocalcaemia (<2.2)
May be artefactual due to low albumin and also if phosphate is high (renal failure) as PO4 chelates calcium rendering it useless
Causes
Osteomalacia
Acute pancreatitis
Hypoparathyroidism (iatrogenic)
Pseudohypoparathyroidism
Hypomagnaesia
Vitamin D deficiency
Renal failure
High phosphate
Failure to retain Ca
Failure to activate Vit D
Signs and Symptoms
Cramps
Peri-oral paraesthesia
spasms
Chovsteks/Trousiers
Anxiety/irritability
Confusion/disorientation
seizures Ix
Bone profile
ECG
Management
Calcium replacement orally
IV calcium gluconate if severe
Alfacalcidol in renal failure

22. Case
48 year old gentleman presents with a 4/52 history of increasing fatigue and anorexia
He has also noticed he has lost some weight and that his skin, especially around his armpits looks darker than usual
He complains of feeling lightheaded on standing and occasionally even when sitting

23. Case BP sitting 110/65, standing 83/45 FBC – Hb 122, WCC 8.4, plt 352
U&Es – Na 130, K 5.9, urea 9.2, creat 112
LFTs – normal
TFTs – normal

24. Case What are the investigative abnormalities?
What are the immediate management steps?
Patient assessment and ECG
Correct hyperkalaemia
IV fluids
What is the underlying cause?
Addisons Disease (autoimmune, infective, infiltrative, metastatic disease)
How can this be confirmed?
Short synacthen test
What is the management?
Steroid replacement

25. Any questions?