Renal Function Tests

Renal Function Tests
The Function of Urinary System
1) Excretion: removal of organic waste products from body fluids (urea, creatinine, uric acid)
2) Homeostatic regulation:
Water -Salt Balance
Acid - base Balance
3) Endocrine function: e.g. renin, erythropoietin
How do you know there is renal defect?
• Decreased urine production
• Clinical symptoms
• Tests
Causes of renal function disorders
• Pre-renal e.g. decreased intravascular volume
• Renal e.g. acute tubular necrosis
• Postrenal e.g. ureteral obstruction
Why do renal function tests?
? To identify renal dysfunction.
? To diagnose renal disease.
? To monitor disease progress.
? To monitor response to treatment.
Biochemical tests of renal function
? Glomerular function tests
o Clearance tests- glomerular filtration rate (GFR)

o Plasma creatinine
o Urea, uric acid and ?2-microglobulin
? Renal tubular function tests
o Osmolality measurements
o Specific proteinurea
o Glycouria
o Aminoaciduria
? Urinalysis -general urine examination (GUE)
o Appearance
o Specific gravity and osmolality
o pH
o Glucose
o Protein
o Urinary sediments
Creatinine
The process of creatine synthesis involves 3 amino acids that are naturally found in the human body: arginine, methionine, and glycine. Synthesis primarily takes place in the kidney and liver, with creatine then being transported to the muscles via the blood. Phosphocreatine can anaerobically donate a phosphate group to ADP to form ATP during the first 2 to 7 seconds following an intense muscular or neuronal effort. Conversely, excess ATP can be used during a period of low effort to convert creatine to phosphocreatine. The reversible phosphorylation of creatine (i.e., both the forward and backward reaction) is catalyzed by several creatine kinases. The presence of creatine kinase (CK-MB, MB for muscle/brain) in blood plasma is indicative of tissue damage and is used in the diagnosis of myocardial infarction.[1] The cell s ability to generate phosphocreatine from excess ATP during rest, as well as its use of phosphocreatine for quick regeneration of ATP during intense activity, provides a spatial and temporal buffer of ATP concentration. In other words, phosphocreatine acts as high-energy reserve in a coupled reaction; the energy given off from donating the phosphate group is used to regenerate the other compound - in this case, ATPPhosphocreatine plays a particularly important role in tissues that have high, fluctuating energy demands such as muscle and brain.Creatinine is formed in muscle from creatine phosphate by irreversible, non enzymatic dehydration and loss of phosphate. The 24-hour urinary excretion of creatinine is proportionate to muscle mass.
1 to 2% of muscle creatine spontaneously c