Urea Nitrogen

What the laboratory says this test is for

Urea is the principle waste product of protein catabolism. BUN is most commonly measured in the diagnosis and treatment of certain renal and metabolic diseases. Increased BUN concentration may result from increased production of urea due to (1) diet or excessive destruction of cellular proteins as occurs in massive infection and fevers, (2) reduced renal perfusion resulting from dehydration or heart failure, (3) nearly all types of kidney disease, and (4) mechanical obstruction to urine excretion such as is caused by stones, tumors, infection, or stricture. Decreased urea levels are less frequent and occur primarily in advanced liver disease and in overhydration.

What the laboratory says this test is for

The BUN/Creatinine ratio is useful in the differential diagnosis of acute or chronic renal disease. Reduced renal perfusion, e.g., congestive heart failure, or recent onset of urinary tract obstruction will result in an increase in BUN/Creatinine ratio. Increased urea formation also results in an increase in the ratio, e.g., gastrointestinal bleeding, trauma, etc. When there is decreased formation of urea as seen in liver disease, there is a decrease in the BUN/Creatinine ratio. In most cases of chronic renal disease the ratio remains relatively normal.

What the laboratory says this test is for

This test estimates urea clearance based on the measurements of urea nitrogen levels in a blood specimen and a 24-hour urine specimen [1]. Urea clearance may be helpful in screening for chronic kidney disease and predicting glomerular filtration rate (GFR) in patients with advanced kidney dysfunction [1].Urea is the main nitrogen-containing product of protein breakdown, and approximately 90% of the urea excretion is through the kidneys. In individuals with normal kidney function, urea clearance is roughly half of creatinine clearance owing to tubular back-diffusion of urea to blood and making it a poor alternative to assess kidney function [1]. Averaging creatinine clearance and urea clearance is also not recommended for this purpose owing to its inferior performance [2]. However, in patients with advanced kidney dysfunction, as the urea back-diffusion decreases urea clearance may better reflect GFR [1].Blood urea levels, commonly expressed by the concentration of blood urea nitrogen (BUN), may be increased in individuals on a high-protein diet or with increased protein breakdown, gastrointestinal hemorrhage, chronic heart failure, or treatment with cortisol [2]. BUN level may be decreased in individuals with low-protein diet and end-stage liver disease [2].Urinary urea levels, commonly expressed by the concentration of urinary urea nitrogen, may be increased in individuals with hyperthyroidism or excess protein intake or breakdown [3]. Urinary urea nitrogen level may be decreased in individuals with malnutrition, kidney damage or insufficiency, low-protein and high-carbohydrate diet, or liver disease. Pregnant persons and healthy children may also have low urinary nitrogen levels [3].The results of this test should be interpreted in the context of pertinent clinical and family history and physical examination findings.References1. Oh MS, et al. Evaluation of renal function, water, electrolytes, and acid-base balance. In: McPherson RA, et al, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Elsevier; 20212. Lamb EJ, et al. Kidney function tests. Rifai N, et al. eds. Tietz Textbook of Laboratory Medicine. 7th ed. Elservier Inc; 20223. Rao LV, et al. Laboratory tests. In: Rao LV, eds. Wallach's Interpretation of Diagnostic Tests. Pathways to Arriving at a Clinical Diagnosis. 11th ed. Wolters Kluwer; 2020.

What the laboratory says this test is for

This panel comprises a group of 7 specific tests that provide information on the status of an individual's blood electrolytes, glucose levels, kidney status, and acid-base balance. The panel is usually ordered as part of a routine health examination or physical [1].The Basic Metabolic Panel is also commonly ordered during hospital and emergency room admission, and to monitor the metabolism and vital signs of hospitalized individuals with conditions, such as hypertension, who are being treated with diuretics or other appropriate interventions. [1].Significant changes in electrolytes, acid-base balance, renal function, and blood glucose may be associated with kidney failure, respiratory distress, and impaired cognitive status. Changes in sodium, potassium, and calcium alter the excitability of neurons, cardiac, and skeletal muscles that can produce arrhythmias, weakness, and spasms/tremors [1].The results of the panel components are usually evaluated jointly for patterns. The section below outlines the roles of the analytes assessed with this panel [1].Sodium: An electrolyte that plays a central role in maintaining the normal distribution of water and appropriate pressure to assure that substances do not leak from cells and organs. Sodium measurements are useful in the diagnosis and treatment of diseases involving electrolyte imbalance.Potassium: An electrolyte that is essential for proper muscle and nerve function and helps keep the balance of fluids. Potassium measurements are useful in assessing electrolyte balance in the diagnosis and treatment of conditions characterized by low or high blood potassium levels.Chloride: An electrolyte that helps maintain volume, acidity, and electrical neutrality of the body fluids. Chloride measurements are useful in the diagnosis and treatment of electrolyte and metabolic disorders, such as cystic fibrosis and diabetic acidosis.Carbon dioxide (bicarbonate): A type of blood gas used to evaluate the total carbonate buffering system and acid-base balance. Carbon dioxide is generally evaluated with other common electrolytes; the measurements are useful in the diagnosis and treatment of numerous potentially serious disorders associated with changes in body acid-base balance.Glucose: A type of sugar that serves as the body's main energy source. Glucose measurements are useful in the diagnosis of diabetes and low blood sugar.Blood urea nitrogen (BUN): The principal waste product of protein catabolism. BUN measurements are useful in the diagnosis and treatment of certain kidney and metabolic diseases.Creatinine: A waste product of the muscles. Creatinine measurements are useful in the evaluation of kidney function and in monitoring renal dialysis.References1. Rao LV, et al. Laboratory tests. In: Rao LV, eds. Wallach's Interpretation of Diagnostic Tests. Pathways to Arriving at a Clinical Diagnosis. 11th ed. Wolters Kluwer; 2020

What the laboratory says this test is for

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