The kidneys are two bean-shaped organs situated in the posterior part of the abdomen on each side of the vertebral column & the right kidney is placed slightly lower than the left to accommodate the liver.
Overview of the Renal Function:
- Regulation of the volume and composition of the body fluids:
- Body fluid osmolality and volume
- Electrolyte balance
- Acid-base balance
- Excretion of metabolic products
- Secretion of hormones
Purpose of the Renal Function Tests
- To evaluate kidney function and aid in the diagnosis of kidney disease.
- To monitor the progression of renal insufficiency.
- The BUN-to-creatinine ratio may aid in the evaluation of a person’s state of hydration.
- A diet rich in meats can cause transient elevations of serum creatinine and creatinine clearance.
- A high-protein diet or dehydration elevates BUN levels.
- Exercise may increase creatinine clearance.
- Some medications may affect BUN levels, serum creatinine, and creatinine clearance.
Creatinine: High creatinine levels is suggestive of Renal Damage
Renal Function Test:
- Blood urea nitrogen (BUN)Test: It provides a measurement of the glomerular filtration rate, the rate at which blood is filtered in the kidneys. Urea is formed in the liver as an end product of protein metabolism and is carried to the kidneys for excretion. Nearly all kidney diseases cause inadequate excretion of urea, elevating BUN levels in the blood. (Other causes of high BUN levels include gastrointestinal bleeding and steroid treatment.) It can be done to determine the amount of urea nitrogen in the blood.
- Serum Creatinine Test: Creatinine is a breakdown product of creatine, an important component of muscle. The production of creatinine depends on muscle mass, which varies very little. Creatinine is excreted exclusively by the kidneys, and its level in the blood is proportional to the glomerular filtration rate. The serum creatinine level (serum is the clear liquid that remains after whole blood has clotted) provides a more sensitive test of kidney function than BUN because kidney impairment is almost the only cause of elevated creatinine. It can also be measured with a urine test.
Creatinine clearance Test: It determines how efficiently the kidneys are clearing creatinine from the blood and serves as an estimate of kidney function. For renal function test, urine and serum levels of creatinine are measured, as well as the volume of urine excreted over a 24-hour period. The creatinine clearance rate is then calculated and expressed as the volume of blood, in milliliters, that can be cleared of creatinine in 1 minute. A low creatinine clearance value indicates abnormal kidney function. It requires both a urine and blood sample.