U+E
U+E is the most commonly requested investigation in biochemistry. The usual tests included within this request are the measurement of plasma sodium, potassium, urea and creatinine. It's main use is as an indicator of kidney function. The basics regarding U+E interpretation can be found in the student doctor section which covers each of the analytes within the U+E request in detail.
An important general principal in U+E interpretation is to remember that a common cause of electrolyte disturbance is drugs. So always check the medication for culprits!
Sodium
Hypernatraemia - an elevated sodium is usually due to too little water rather than too much sodium ie dehydration. See the flowchart for further details.
Hyponatraemia - a low sodium is often due to too much water rather than too little sodium. Drugs are a very common cause of hyponatraemia. See the flowchart for further details.
Potassium
Hyperkalaemia - common causes of an elevated potassium are haemolysis, drugs and renal failure. See the flowchart for further details.
Hypokalaemia - the commonest cause of a low potassium is drugs. If not medication, then investigations are directed at looking at potassium loss from the gut or kidneys. See the flowchart for further details.
