Kidney Function Tests (Renal Function Tests) PDF

Kurdistan Regional Government – Iraq Ministry of Higher Education & Scientific Research University of Duhok College of Health Sciences Department of Medical Laboratory Sciences Kidney Function Tests (Renal Function Tests)...

Kurdistan Regional Government – Iraq Ministry of Higher Education & Scientific Research University of Duhok College of Health Sciences Department of Medical Laboratory Sciences Kidney Function Tests (Renal Function Tests) Biochemistry Practical Lecture 2nd stage- 3rd semester Barhav Issa Abdullah BIOCHEMIST  Kidney The kidneys play a central role in excretion of many metabolic breakdown products, including ammonia and urea from protein, creatinine from muscle, uric acid from nucleic acids, drugs and toxins. They achieve this by making large volumes of an ultrafiltrate of plasma (120 mL/min, 170 L/24 hrs) at the glomerulus, and selectively reabsorbing components of this ultrafiltrate at points along the nephron. 10/29/2024 Barhav Issa Abdullah (BIOCHEMIST) 2 Nephron Each kidney contains approximately 1 million individual functional units, called nephrons. Each nephron consists of: 1. glomerulus, which is responsible for ultrafiltration of blood, 2. a proximal renal tubule, Returns the bulk of each valuable substance back to the blood circulation. 3. a loop of Henle, Facilitates the reabsorption of water, sodium, and chloride. 4. a distal renal tubule and a collecting duct, which together are responsible for selective reabsorption of water and electrolytes that have been filtered at the glomerulus. Over 99% of this filtered fluid is reabsorbed into the blood in the peritubular capillaries during its passage through successive segments of the nephron, largely as a result of tubular reabsorption of sodium. 10/29/2024 Barhav Issa Abdullah (BIOCHEMIST) 3 10/29/2024 Barhav Issa Abdullah (BIOCHEMIST) 4 Kidney functions Regulation of : - water and electrolyte balance. - acid base balance. - arterial blood pressure. Excretion of metabolic waste products and foreign chemicals. Hormonal Function: Secretion of erythropoietin & activation of vitamin D and activation of angiotensinogen by renin Metabolic function: Along with liver site for gluconeogenesis 10/29/2024 Barhav Issa Abdullah (BIOCHEMIST) 5 Renal Function Tests: Renal function tests include: Blood urea, Serum creatinine and Creatinine clearance. The non-protein nitrogenous compounds include urea, creatinine, creatine and uric acid. Urea, creatinine and uric acid are the end products of protein metabolism. They are waste products that should be eliminated from the body. The kidney is the main route of elimination of most of these waste products 10/29/2024 Barhav Issa Abdullah (BIOCHEMIST) 6 Renal Function Tests: Many diseases affect renal function. With progressive renal insufficiency, there is retention of urea, creatinine and uric acid in the blood. General Biochemical tests such as blood levels of urea, creatinine and uric acid are mainly of value in detecting presence of these diseases 10/29/2024 Barhav Issa Abdullah (BIOCHEMIST) 7 Purpose of Renal function tests To assess functional capacity of kidneys To diagnose renal impairment To assess the severity and progression of renal impairment To assess the effectiveness of treatment 10/29/2024 Barhav Issa Abdullah (BIOCHEMIST) 8 ESTIMATION OF BLOOD UREA Clinical Significance: Urea is the end product of protein metabolism. Hepatic enzymes convert ammonia from amino acids to urea. More than 90 % of urea is excreted through the kidneys in the urine. Decrease urea level: Acute liver destruction and accompanied with increase ammonia level. 10/29/2024 Barhav Issa Abdullah (BIOCHEMIST) 9  Elevated urea, Blood urea may increase (uremia) in: Diet with excess of proteins. Renal disease (e.g. acute or chronic renal failure). Heart failure Gastrointestinal hemorrhage Dehydration Renal obstruction 10/29/2024 Barhav Issa Abdullah (BIOCHEMIST) 10 Blood urea nitrogen (BUN) test The blood urea nitrogen (BUN) test is a measure of the amount of nitrogen in the blood in the form of urea. Normal human adult blood should contain between ( 7 to 20 mg/dL)of urea nitrogen in blood. To convert blood urea nitrogen to urea, divide by 2.14 10/29/2024 Barhav Issa Abdullah (BIOCHEMIST) 11 Converting BUN to Urea each molecule of urea having 2 nitrogen, each of molar mass 14 g/mol. To convert BUN to urea in mg/dL by using following formula: MW of urea = 60; urea nitrogen = 28; Therefore, BUN = 60/28 = 2.14 10/29/2024 Barhav Issa Abdullah (BIOCHEMIST) 12 Laboratory measurement of urea Specimen Collection: - Serum or plasma - non fasting specimen is acceptable 10/29/2024 Barhav Issa Abdullah (BIOCHEMIST) 13 Principle of the test: Enzymatic colorimetric method based on the specific action of urease which hydrolyzes urea in the sample into ammonium ions and carbon dioxide. Then ammonium ions react with salicylate and Sodium hypochlorite (NaClO), in the presence of the catalyst nitroprussiate, to form a green complex “indophenol”: The intensity of color of the final product is directly proportional to the urea concentration in the sample. 10/29/2024 Barhav Issa Abdullah (BIOCHEMIST) 14 Reagents: Urea colorimetric kit ❑ R1: Salicylate Nitroprussiate ❑ R2: Urease ❑ R3: Na-hydrochlorate NaOH ❑ R4: Standard urea (40mg/dl) 10/29/2024 Barhav Issa Abdullah (BIOCHEMIST) 15  Manual procedure: Urea colorimetric kit Test Tubes Blank Standard Test Working reagent 1 ml 1 ml 1 ml R1+R2 Demineralized Water 10 µl standard (R4) 10 µl Specimen 10 µl Mix well then wait for 4 minutes at room temperature or 2 minutes at 37˚c, then add: Base diluted (R3) 1 ml 1 ml 1 ml Mix. Let stand for 8 minutes at room temperature. Read absorbance at 600 nm against reagent blank. 10/29/2024 Barhav Issa Abdullah (BIOCHEMIST) 16 Calculation: A = Absorbance, measured by spectrophotometer. Urea standard concentration = 40 mg/dl. 10/29/2024 Barhav Issa Abdullah (BIOCHEMIST) 17  Manual procedure: Urea U.V kinetic method Test Tubes Standard Assay Reagent 1 ml 1 ml Standard 10 µl Specimen 10 µl Mix. Start timer after 30 seconds record absorbance A1 at 340 nm and then Absorbance A2 after 90 seconds Note: serum, plasma or urines diluted (1+19) in demineralized water 10/29/2024 Barhav Issa Abdullah (BIOCHEMIST) 18 Calculation: A = Absorbance, measured by spectrophotometer. Urea standard concentration = 40 mg/dl. 10/29/2024 Barhav Issa Abdullah (BIOCHEMIST) 19  Expected value: in normal adults (male & female): - Blood urea: 15 - 45 mg/dl. - Blood urea nitrogen (BUN): 7 - 20 mg/dl Note: Blood urea ≈ BUN x 2.14 10/29/2024 Barhav Issa Abdullah (BIOCHEMIST) 20