Kidney Function Test PDF

Kidney function test Kidney Functions:- Remove waste products from the body. Remove drugs from the body. Balance the body's fluids. Release hormones that regulate blood pressure. Produce an active form of vitamin D that promotes strong and healthy bones. Releases erythr...

Kidney function test Kidney Functions:- Remove waste products from the body. Remove drugs from the body. Balance the body's fluids. Release hormones that regulate blood pressure. Produce an active form of vitamin D that promotes strong and healthy bones. Releases erythropoietin hormone that controls the production of red blood cells.  Nephrotic syndrome is a kidney disorder that causes our body to pass too much protein in urine. Nephrotic syndrome is usually caused by damage to the clusters of small blood vessels in our kidneys that filter waste and excess water from our blood. Alport syndrome is a genetic condition characterized by kidney disease. It occurs due to an abnormality of a gene that codes for type 4 collagen and usually presents in patients with hematuria.  NON-PROTEIN NITROGENOUS (NPN) COMPOUNDS ▪ These are nitrogen containing compounds that are not proteins or polypeptides. ▪ The determination of NPN substances in the blood has traditionally been used to monitor renal function. ▪ NPN fraction comprises of many compounds. ▪ Majority of these compounds arise from catabolism of proteins and nucleic acids. ▪ Total NPN compounds in plasma is 25 to 60 mg/dL which include the following main fractions:  Total NPN compounds 25 - 35 g/day ▪ Urea 25 g ▪ Uric acid 400-600 mg ▪ Creatinine 1.4 g ▪ Amino acids 100-200 mg ▪ Ammonia 0.7 g ▪ Creatine 50-150 mg  Urea Urea is the chief end product of protein catabolism. Its excretion is directly related to the protein intake. Normally it comprises 80 to 90 % of the total urinary nitrogen, but on low protein diet the amount of urea is decreased. It is formed in liver, transported into blood stream, and excreted by kidneys in urine.  Causes of increased urea level ❖ Temporarily after a high protein meal. ❖ Renal failure (impaired excretion). ❖ Increased protein catabolism eg. after glucocorticoids. ❖ In Cushing syndrome  Causes of decreased urea level ❖ Severe protein restriction. ❖ Increased protein synthesis eg. during pregnancy, growth and after administration of growth hormone, insulin and testosterone (anabolic hormones). ❖ Severe liver diseases which result in decreased urea synthesis. ❖ Acidosis due to increased ammonia production.  Ammonia It is formed in the renal tubular epithelium 60 % by glutaminase enzyme (converts glutamine to glutamate and NH3) the remainder by deamination of other amino acids. It is passed into the tubular urine where, it combines with H+ forming NH4+, thus lowering H+ concentration and allowing further passage of H+ into lumen in exchange for Na+. Ammonia excretion is increased in the following conditions: ❖Acidosis eg. ketosis, ingestion of acids or acid forming substances as NH4Cl. ❖High protein diet (increased production of acids).  Ammonia excretion is decreased in the following conditions: ❖All cases of alkalosis. ❖Acidosis of renal origin (Failure of ammonia excretion).  Uric acid It is formed by catabolism of purines (nucleoproteins) in liver and excreted by kidneys in urine. In urine of average pH (6.0) uric acid is present largely as soluble sodium and potassium salts, whereas in highly acid urine the insoluble free form predominates and precipitates from solution.  Causes of increased uric acid levels - Gout (Also known as “disease of kings”) a- Metabolic: increased production which may be primary (due to genetic causes) or secondary (due to diseases that increase nucleoprotein catabolism as cancer) b- Renal: decreased excretion  Causes of decreased uric acid levels Severe liver damage (due to decreased production). Enzyme deficiency causing hypouricemia eg. xanthine oxidase, adenosine deaminase and purine nucleoside phosphorylase. RENAL FUNCTION TESTS A common marker of kidney disease is proteinuria, which is first detectable as microalbuminuria (i.e. >30 mg albumin in a 24-hour urine collection). Dipstick urinalysis is used to monitor the patients with suspected and diagnosed renal failure.  Major Renal Function Tests include: A. URINE ANALYSIS Complete urine analysis provides valuable information on renal function. Physical characteristics—assessment of volume, color, odor, appearance, specific gravity and pH. Chemical characteristics—checking for the presence of abnormal constituents like protein, reducing sugar, ketone bodies, blood, bile salts and bile pigments. Microscopy—checking for the presence of WBCs, RBCs and casts. B. SERUM MARKERS OF RENAL FUNCTION Serum creatinine Serum creatinine is a simple test used to evaluate renal function. Serum urea (or blood urea nitrogen) C. ESTIMATION OF GLOMERULAR FILTRATION RATE (GFR) Endogenous creatinine clearance test Inulin clearance test Urea clearance test D. TESTS OF RENAL TUBULAR FUNCTION Water deprivation test Urine acidification test