Creatinine results from a metabolic breakdown of creatine phosphate, an amino acid compound used in skeletal muscle contraction. According to the "Mosby's Manual of Diagnostic and Laboratory Tests," the daily production of creatine and creatinine depends on a person's muscle mass, which minimally fluctuates under normal circumstances. The kidneys are entirely responsible for excreting creatinine out of the body, thus blood creatinine levels directly relate to the function of the kidneys. Another renal function test called blood urea nitrogen is usually interpreted along with creatinine levels to assess kidney status.
Kidney Disorders
According to the American Association for Clinical Chemistry, abnormal elevation in serum creatinine levels indicates a disorder of the kidneys and impaired renal function. These disorders include glomerulonephritis characterized by inflammation of the blood vessels in the kidneys, bacterial infection of the kidneys or pyelonephritis and acute tubular necrosis, or cell death in the kidneys' small tubes caused by toxic substances. Obstruction of the urinary tract, such as with prostate disease or kidney stones, can also cause impaired kidney function and lead to elevated creatinine levels, states the AACC.
Reduced Blood Supply
When underlying medical conditions affect normal blood flow to the kidneys, renal function becomes impaired thus increasing creatinine levels in the blood. Shock, or a sudden critical drop in blood flow to the body, compromises renal status because the kidneys are not being nourished. Dehydration causes reduced renal blood flow, as well. In people with congestive heart failure, the heart is not adequately pumping blood towards the kidneys and other organs. Atherosclerosis, or narrowing of the arteries, and diabetic nephropathy are other conditions that reduce blood flow to the kidneys. According to Medline Plus, complications of pregnancy such as pre-eclampsia and eclampsia can impair renal function and increase creatinine values.
Muscle Mass Changes
Increased muscle mass indicates increased creatine phosphate, which translates to increased creatinine levels in the blood. Acromegaly and gigantism are disorders caused by abnormality of the pituitary gland and can be associated with increased muscle mass. When an injury of the skeletal muscle causes release of muscle fiber contents called myoglobin into the blood, the condition is known as rhabdomyolysis. Myoglobin in large amounts has a nephrotoxic effect on the kidneys, according to the "Mosby's Manual of Diagnostic and Laboratory Tests."
References
- "Mosby's Manual of Diagnostic and Laboratory Tests"; Pagana & Pagana; 2006
- Lab Tests Online: Creatinine
- Medline Plus: Creatinine - Blood
