Creatinine and bun relationship

creatinine and bun relationship

Serum Creatinine: Creatinine is a waste product in your blood that comes kidneys, but when kidney function slows down, the BUN level rises. A BUN test may be done with a blood creatinine test. The level of creatinine in your blood also tells how well your kidneys are working—a high creatinine level. Creatinine and urea blood levels reflect glomerular filtration rate (GFR) . correlation between estimated blood loss and plasma urea concentration among

How to measure renal function in clinical practice. BMJ Clinical research ed. McWilliam A et tal. Laboratory tests of renal function. Blood urea nitrogen and creatinine.

Emerg Med Clin North Am ; 4, 2: Jurado R et tal. The decreased serum urea nitrogen-creatinine ratio. Arch Intern Med ; Snook JA et tal. Value of a simple biochemical ratio in distinguishing upper and lower sites of gastrointestinal haemorrhage. Lancet ; 1, Felber S et tal. J Pediatr Gestroenterol Nutr ; 7, 5: Olsen LH et tal. Stools containing altered blood-plasma urea: Br J Surg ; 78, 1: Ernst AA et tal.

creatinine and bun relationship

Am J Emerg Med; 17, 1: Sittichanbuncha Y et tal. How to differentiate sites of gastrointestinal bleeding in patients with hematochezia by using clinical factors? Gastroenterol Res Pract ; Kim KS et tal. Pediatr Gastroenterol Hepatol Nutr ; 18, 1: Srygley FD et tal. Does this patient have a severe upper gastrointestinal bleed? JAMA ; Pumphrey CW et tal. Raised blood urea concentration indicates considerable blood loss in acute upper gastrointestinal haemorrhage.

Br Med J ; Blatchford O et tal. A risk score to predict need for treatment for upper-gastrointestinal haemorrhage. Lancet ; Stevenson J et tal. Validating the Glasgow-Blatchford upper GI bleeding scoring system. Gut ; 62, 2: The principle behind hemodialysis is the diffusion of solutes through a semi permeable membrane.

Hemodialysis is usually performed with uremic patients for two to three times a week and the required times for dialysis vary from two to four hours [ 8 ]. The difference in the time of dialysis depends on various factors, including kidney function, amount of waste in body, level of salts and body weight.

Dialysis improves many symptoms of kidney failure, but some problems including hypertensionanemia and itch often require additional drug treatments as well [ 9 ].

creatinine and bun relationship

The progression of kidney damage is marked by the rise in two important chemical substances in the blood - creatinine and urea whose evaluation in serum helps to assess Glomerular Filtration Rate GFR followed by renal function. However, neither creatinine nor urea is directly toxic and they are only a measure of kidney function [ 10 ].

Creatinine is produced from muscles and is excreted through the kidneys along with other waste products. Creatinine concentration in serum is maintained by the balance between its generation and excretion by the kidneys. Males have higher serum creatinine levels than females because males have greater muscle mass. The quantity of creatinine in serum depends on their generation, glomerular filtration and tubular secretion of serum creatinine.

Calculations based on serum creatinine and the age groups of the patient are used to estimate more precisely the degree of kidney function [ 1213 ]. These calculated values are called the estimated glomerular filtration rate or eGFR.


These results are known as creatinine clearance [ 14 ]. Other factors affecting creatinine concentrations include age, sex, ethnicity, body habits and diet. However, neither creatinine nor urea are directly toxic and are just substances used to measure kidney function [ 15 ]. Urea is an organic compound and plays a vital role in the metabolism of nitrogen-containing compounds.

It is a waste product from dietary protein and is also filtered into urine by the kidneys [ 1617 ]. Urea nitrogen is a normal waste nitrogen product found in blood that comes from the breakdown of protein from foods. Healthy kidneys remove urea nitrogen from blood, but the level of urea in blood rises with kidney failure occurs [ 4 ].

✔✔✔ What is BUN and Creatinine - Kidney Function Test ✔✔✔

Materials and Methods Patients and samples collection Random samples from patients with renal failure were collected from Dr.

Also chloral hydrate and guanethidine have been observed to increase BUN values. This reaction is nonspecific and subject to interference from many noncreatinine chromogens, including acetone, acetoacetate, pyruvate, ascorbic acid, glucose, cephalosporins, barbiturates, and protein. It is also sensitive to pH and temperature changes.

Urea and creatinine concentration, the urea:creatinine ratio

One or another of the many modifications designed to nullify these sources of error is used in most clinical laboratories today.

For example, the recent kinetic-rate modification, which isolates the brief time interval during which only true creatinine contributes to total color formation, is the basis of the Astra modular system.

One of these, an automated dry-slide enzymatic method, measures ammonia generated when creatinine is hydrolyzed by creatinine iminohydrolase. Its simplicity, precision, and speed highly recommend it for routine use in the clinical laboratory.

Only 5-fluorocytosine interferes significantly with the test. Creatinine must be determined in plasma or serum and not whole blood because erythrocytes contain considerable amounts of noncreatinine chromogens.

To minimize the conversion of creatine to creatinine, specimens must be as fresh as possible and maintained at pH 7 during storage. Its primary source is dietary protein. In the hepatocyte, the amino acids are deaminated and transaminated. The resulting excess nitrogen feeds into the urea cycle to be incorporated into urea. The protein moieties escaping absorption by the small bowel, plus recycled urea, are converted into ammonia by gut flora predominantly in the colon.

The ammonia diffuses through the portal circulation into the liver to enter the urea cycle Figure Modified from Raforth and Onstad, The amount of urea produced varies with substrate delivery to the liver and the adequacy of liver function. It is increased by a high-protein diet, by gastrointestinal bleeding based on plasma protein level of 7. It is decreased by low-protein diet, malnutrition or starvation, and by impaired metabolic activity in the liver due to parenchymal liver disease or, rarely, to congenital deficiency of urea cycle enzymes.

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The normal subject on a 70 g protein diet produces about 12 g of urea each day. This newly synthesized urea distributes throughout total body water. Some of it is recycled through the enterohepatic circulation.

Usually, a small amount less than 0. The bulk of the urea, about 10 gm each day, is excreted by the kidney in a process that begins with glomerular filtration. Low flow, as in urinary tract obstruction, allows more time for reabsorption and is often associated with increases in antidiuretic hormone ADHwhich increases the permeability of the terminal collecting tubule to urea.

During ADH-induced antidiuresis, urea secretion contributes to the intratubular concentration of urea. The subsequent buildup of urea in the inner medulla is critical to the process of urinary concentration.

creatinine and bun relationship

Reabsorption is also increased by volume contraction, reduced renal plasma flow as in congestive heart failure, and decreased glomerular filtration. Creatinine formation begins with the transamidination from arginine to glycine to form glycocyamine or guanidoacetic acid GAA. This reaction occurs primarily in the kidneys, but also in the mucosa of the small intestine and the pancreas.

In a reaction catalyzed by creatine phosphokinase CPKmost of this muscle creatine is phosphorylated to creatine phosphate. Modified from Dosseter, Thus, creatinine production essentially reflects lean body mass. Because this mass changes little from day to day, the production rate is fairly constant. Absolute creatinine production declines with age in line with decreasing muscle mass. Unlike urea, creatinine is largely unaffected by gastrointestinal bleeding or by catabolic factors such as fever and steroids.

However, the ingestion of cooked meat can raise the sCr because cooking converts the creatine in meat to creatinine.