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Urea & Electrolytes (U&E) – Sodium, Potassium, Chloride, Bicarbonate, Urea and Creatinine

Urea & Electrolytes (U&E) – Sodium, Potassium, Chloride, Bicarbonate, Urea and Creatinine

Code:
ELECT

Sample Type:

Serum (Gold Top)

Minimum volume: 1 mL

Ref Ranges/Units:

Sodium – 133 – 146 mmol/L. Results <120 (<130 if <16 years) and >160 mmol/L will be phoned.

Potassium – 3.5 – 5.3 mmol/L. Results <2.5 and >6.5 mmol/L will be phoned.

Chloride – 95 – 108 mmol/L

Bicarbonate – 22 – 28 mmol/L. Results <10 mmol/L will be phoned.

Urea – 2.5 – 7.8 mmol/L. Results >30 mmol/L (>10 if <16 years, >25 if >70 years (GP only)) will be phoned.

Creatinine:
Female 45 – 85 μmol/L
Male 60 – 105 μmol/L
Results >354 μmol/L (>200 if <15 years) will be phoned.

eGFR 90 – 120 ml/min/1.73m²

New stage AKI alerts will be phoned (Stage 1 if K+ >6 mmol/L).

Turnaround:

Same Day (60 minutes from receipt for Urgent Samples)

Special Precautions/Comments:

Additional Information:

A urea and electrolyte (U&E) panel is commonly used to assess renal function and fluid and electrolyte status. It is also useful in the investigation of acid-base disturbances (usually alongside an arterial blood gas). Electrolytes contribute to serum osmolality.

Sodium (Na+) – major extracellular cation critical in maintaining fluid balance and plasma volume. Imbalances can result in changes in blood pressure, fluid overload (oedema), seizures, delirium and coma/death. Can be underestimated in patients with high total protein or lipids.

Potassium (K+) – major intracellular cation important in maintaining membrane resting potential. Potassium is therefore critical for propagation of action potentials for muscle contraction and neurotransmitter release. Small changes in potassium can therefore affect cardiac rhythm. It is also important in acid-base balance. May be spuriously raised in sample haemolysis, delays in centrifugation, K-EDTA contamination. May also be raised in thrombocytosis and leukocytosis due to leakage of potassium during clotting.

Chloride (Cl-) – major extracellular anion important in maintaining electroneutrality and acid-base status. Level of chloride usually mirror that of sodium, and is commonly found as sodium-chloride (NaCl). Measured but not routinely reported.

Bicarbonate (HCO3) – anion critical for maintaining a stable pH level and electroneutrality.

Anion gap – calculated based on difference in cations and anions (Sodium + potassium) – (chloride + bicarbonate). Can be useful to investigate cause of acid-base disturbance.

Urea – nitrogenous waste product made from breakdown of proteins. Cleared from serum and excreted by the kidney, therefore measurement allows assessment of renal function.

Creatinine – product of skeletal muscle breakdown. Cleared from serum and excreted by the kidney, therefore measurement allows assessment of renal function. Considered a better marker of renal function than urea and used to calculate the estimate glomerular filtration rate (eGFR). However, less accurate in extremes of muscle mass, where cystatin C may be a more appropriate marker.

Estimated glomerular filtration rate (eGFR) – calculated parameter which estimates renal function. Calculated using the CKD-EPI equation based on 3 variables (serum creatinine, age and sex).

Acute Kidney Injury (AKI) alert – algorithm which detects sudden increases in serum creatinine relative to a reference value (lowest creatinine recorded within 3 months of event if available). Staged 1-3 based on severity.