Veterinary Clinical Biochemistry and Laboratory Diagnosis-II

ASSESSING RENAL FUNCTIONS

 The kidney function tests include

• Blood test - Serum creatinine analysis,Urea estimation, Haemoglobin,phosphorus,potassium and calcium estimation.
• Urinalysis
• Clearance test
• Renal pyelography
• Ultra sound scan

 Investigations

 Urinalysis

Appearance	Blood, colour, turbidity.
Specific gravity	Sticks measure ionic particles only, not glucose.
pH	Normally acidic, except after a meal.
Glucose	Its presence may indicate increased blood glucose, or tubular disorder
Protein	Its presence may be due to: glomerular leak, raised serum proteins, Bence-Jones proteins myoglobulin, or of -renal origin
Microscopy	UTI will show polymorphs with no casts acute glomerulonephritis will show cells and casts Chronic glomerulonephritis shows little sediment

Glomerular filtration rate (GFR)

• This is the most frequent test of renal function.
• GFR varies as a function of normal physiology as well as disease.
• Its measurement is based on determining the volume of plasma from which a substance is removed by glomerular filtration during its passage through the kidney. In other words, the clearanceof that substance, Clearance = (U x V) / P Where U = urinary concentration of X; V = rate of urine formation (ml/min); P = plasma concentration of X.

Creatinine Clearance

• It is often used as a rough measurement of GFR, with a timed urine collection (often 24 hrs).
• And a blood sample taken to measure plasma creatinine during that time period.
• It is limited by problems of accurate urine collection and tends to overestimate the GFR.

 Estimated GFR

• The plasma creatinine concentration (alone) is only a very rough guide to renal function.
• Creatinine is produced by the muscles at a relatively constant level by the body.
• So, the plasma concentration therefore depends on the rate of excretion by the kidneys.
• Levels are affected by age, gender, ethnic group, muscle bulk, ingestion of cooked meat, malnutrition and after use of some drugs.