Urea is created by the liver and is then carried by the blood to the kidneys for excretion. To test for kidney (renal) failure, measuring the amount of urea nitrogen that is left in the blood after the urea is cleared from the bloodstream by the kidneys indicates how well the kidneys are functioning.
Dehydration means that a person has lost too much fluid or isn't drinking enough fluids. Vomiting and diarrhoea can cause dehydration. Extreme dehydration is life-threatening.
Urea is filtered by the kidney but it also reabsorbed. The amount of urea that is reabsorbed goes up when a person is dehydrated. BUN, or blood urea nitrogen, measures the amount of urea nitrogen that is in the blood. Urea nitrogen is a waste product of protein metabolism. Dehydration can result in an increase in BUN level which is referred to as azotemia. The BUN level can also increase if a person has eaten too much protein, has a haemorrhage in the gastrointestinal tract, is in shock, has impaired renal function or congestive heart failure that is the outcome of poor renal perfusion or acute myocardial infarction. Anyone who is extremely dehydrated can have a high BUN because of the lack of fluid volume needed to excrete waste materials from the body.
Over-hydration, on the other hand, can cause decreased BUN. When a person is suffering from SIADH, which means "syndrome of inappropriate antidiuretic secretion," the antidiuretic hormone that is in charge of stimulating the kidneys and helping them to conserve water isn't doing its job and instead causes too much water to be retained in the bloodstream. This waste is not excreted in urine as it should be. SIADH causes the BUN level to go down because the volume of fluid in the bloodstream has gone up.
U&E, which is an urea and electrolytes test, can be done to see if dehydration or kidney failure is present as well as to discover any abnormalities that are present in the blood chemistry, according to Healthengine.com.au. When dehydration is present, the urea and/or creatinine will be high. Creatinine is a metabolic byproduct of muscle metabolism, according to Critical Care Medicine Tutorials. It is filtered and then excreted by the kidney