What is the significance of urea

Overhydration induces increased GFR and consequent increased excretion of urea. Concentration in patients with renal dysfunction can range from mildly increased to severely increased, depending on severity of disease. The limitation of urea as a test of renal function relates to reduced sensitivity and specificity so that a normal urea does not necessarily exclude renal disease and a slight to moderate increase in urea cannot be assumed to be due to renal disease.

There are many non-renal causes that can be associated with such a rise and for some of these conditions, e. By comparison with urea, creatinine measurement is no more sensitive but is more specific. Under some circumstances urea may be more sensitive for detection of early renal disease than creatinine, so it has some advantage. These issues will be explored further in a second article that will focus on the clinical value of measuring urea and creatinine together and calculating the urea: creatinine ratio.

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Summary This first of two articles on understanding the clinical value of measuring urea concentration dives into the physiological topics, such as urea production and renal processing of urea as well as the causes of increased and reduced urea concentration. By way of introduction, this first article begins with a brief historical perspective.

Urea — a brief historical perspective Urea owns special historical significance compared with most other analytes currently measured in the clinical laboratory or at the point of care. Background physiology - urea production and excretion Urea is a small organic molecule MW 60 comprising two amino NH2 groups and a linked carbamyl C-O group: It is the principal nitrogenous end product of protein and amino acid catabolism.

There are two physiological causes of reduced concentration: low-protein diet, and pregnancy. Decreased renal perfusion due to: heart failure hypovolemic shock severe hypotension Gastrointestinal bleed High-protein diet Ageing Catabolic state: trauma severe infection starvation some drugs with catabolic effect, e. Kurzer F et tal. Urea in the history of organic chemistry: Isolation from natural sources. J Chem Educ ; 33, 9: Rosenfeld L. William Prout: Early 19th century physician-chemist.

Clinical chemistry ; 49, 4: Cohen PS et tal. J Chem Educ ; 73, 9: A permanent preparation of urease, and its use for rapid and accurate determination of urea. Thudichum JLW. On the analysis of urea in urine for clinical purposes. BMJ ; s, Green WE. The practical utility of estimating the amount of urea passed daily. The second step involves the quantitative measurement of ammonium using a variety of methods to determine the amount of urea in the sample.

Tietz Fundamentals of Clinical Chemistry. Philadelphia, PA : Saunders ; Google Scholar. Google Preview. Price C Finney H. Developments in the assessment of glomerular filtration rate. Clinica Chimica Acta.

Measurement of residual glomerular filtration rate in the patient receiving repetitive hemodialysis. Kidney Int. A method for estimating nitrogen intake of patients with chronic renal failure. Cystatin C: an improved estimator of glomerular filtration rate? Clin Chem. Fawcett J Scott E. A rapid and precise method for the determination of urea. J Clin Path. Oxford University Press is a department of the University of Oxford. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide.

Sign In or Create an Account. Sign In. Increasing tertiles of discharge urea were a predictor of reduced 1-year survival HR, 2. Urea was more discriminative than eGFR in predicting long-term survival by area under the receiver operating characteristic curve 0.

Some symptoms and signs of kidney dysfunction include:. High urea levels suggest poor kidney function. This may be due to acute or chronic kidney disease. However, there are many things besides kidney disease that can affect urea levels such as decreased blood flow to the kidneys as in congestive heart failure , shock, stress, recent heart attack or severe burns; bleeding from the gastrointestinal tract; conditions that cause obstruction of urine flow; or dehydration.

Low urea levels are not common and are not usually a cause for concern. They can be seen in severe liver disease or malnutrition but are not used to diagnose or monitor these conditions. Low urea levels are also seen in normal pregnancy. Urea levels increase with age and also with the amount of protein in your diet.

High-protein diets may cause abnormally high urea levels. Very low-protein diets can cause abnormally low urea levels. Lower urea levels are also seen in infants and small children. Drugs that damage kidney function may increase urea levels. Your urea and creatinine may be monitored if you are on certain drugs. Urea and creatinine are often the first tests that are used to check how well the kidneys are able to filter waste products from your blood.

Your doctor may also request electrolyte tests such as sodium and potassium , or calcium to help understand how your kidneys are functioning. Urea levels increase with age. Levels are also slightly higher in men than women. Urea levels are normally slightly lower in pregnancy , especially in the last few months when the foetus is using large amounts of protein for growth.