Us and Es

Question 1

What are the indications for Us and Es?

Answer 1

• to confirm normal renal function

- to exclude an electrolyte imbalance

Question 2

What is included in a Us and Es test?

Answer 2

• urea
• creatinine
• sodium
• potassium
• calcium
• magnesium
• phosphate

Question 3

Urea and creatinine (causes and value uses)

Answer 3

Urea:

• increased: dehydration, GI bleed, increased protein breakdown (eg. surgery, trauma, malignancy), increased protein intake, drugs
• decreased: malnutrition, liver disease, pregnancy

Creatinine: specific for determining kidney injury (creatinine clearance)

When the kidneys are damaged, urea and creatinine clearance decreases and blood concentration increases.

Question 4

What are the causes of hyponatraemia?

Answer 4

• hypovolaemia (Na+ lost): diuretics, Addison’s, kidney injury, diarrhoea, vomiting
• euvolaemic (H20 gained): SIADH, hypothyroidism, glucocorticoid insufficiency
• hypovolaemic/oedema: congestive heart failure, liver cirrhosis, nephrotic syndrome

Question 5

What are the causes of hypernatraemia?

Answer 5

• euvolaemic: iatrogenic (Na+ containing drugs)

- hypovolaemic: fluid loss, diabetes insipidus, osmotic dieresis (eg. DKA)

Question 6

What are the causes of hypokalaemia?

Answer 6

• increased renal secretion: diuretics, steroids, Cushing’s, Conn’s
• other K+ loss: intestinal fluid loss (vomiting and diarrhoea)
• increased cellular uptake: salbutamol, insulin, alkalosis

Question 7

What are the causes of hyperkalaemia?

Answer 7

• decreased renal secretion: acute/chronic kidney injury, drugs (eg. K+-sparing diuretics, ACEi, NSAIDs)
• increased K+: iatrogenic, blood transfusion
• increased cellular release: acidosis, tissue breakdown (rhabdomyolysis, haemolysis)