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Glomerular filtration rate and levels of electrolytes, urea and creatinine give a strong indication of kidney function and can guide treatmentLearning objectives...
After reading this article, you will be able to:
Describe the functions of the kidneys
Explain what electrolyte levels tell us
List the causes and treatment of renal disease
Author
Andrew Blann is consultant at City Hospital, Birmingham, and senior lecturer in medicine, University of Birmingham.Abstract
Blann A (2014) Routine blood tests 1: why do we test for urea and electrolytes? Nursing Times; 110: 5, 19-21.
Urea and electrolytes are the most commonly requested biochemistry tests. They provide essential information on renal function, principally in excretion and homoeostasis. Creatinine levels are a major factor in determining the estimated glomerular filtration rate, which is the gold standard marker of kidney health.
The tests' clinical value is in the diagnosis and management of acute kidney injury and chronic kidney disease, which, if left untreated, can lead to thrombosis and cardiovascular disease such as myocardial infarction and stroke.
This article has been double-blind peer reviewed
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5 practice points
Urea and electrolytes are the most commonly requested biochemistry test
Low sodium levels can cause oedema, which may lead to heart failure
High potassium levels can lead to cardiac arrest and, since treatment is short term, their cause must be established
The glomerular filtration rate is used to assess kidney function
Acute kidney injury can be reversed once the cause has been found but chronic kidney disease can only be slowed
Urea and electrolytes (U&Es) are the most frequently requested biochemistry tests. They provide useful information about several aspects of health, such as the volume of blood and its pH. The most important aspect of U&Es is what they tell us about kidney functioning.Kidney function
The kidneys have the following three main functions:
Homoeostasis: regulating blood volume, and maintaining the acid/base balance (pH) and levels of electrolytes, principally sodium and potassium;
Endocrine activity: regulating blood pressure, supporting red blood cell production and contributing toblood calcium;
Excretion: removing urea and creatinine.
Kidneys consist of millions of single-functional units called nephrons. The top of a nephron...