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The functions of the kidneys include urine production, maintaining normal electrolyte levels, maintaining normal fluid levels and filtering waste from the circulatory system. The kidneys work with hormones and other chemicals to excrete excess fluid and retain fluid when the body does not have enough. Chronic renal failure causes kidney function to decline, which means the kidneys do not carry out these functions properly.
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Fluid & Electrolyte Imbalance
As kidney function declines, the kidneys do not concentrate urine properly. As chronic renal failure progresses, the kidneys do not excrete phosphorus, potassium and other minerals as they should. This problem has several effects. Increased potassium levels have serious risks in the human body. Too much potassium, also known as hyperkalemia, can cause abnormal heart rhythm, muscle cramps and coma. If not treated, hyperkalemia can also lead to death. High phosphorus levels result in a leaching of calcium from the bones, which increases the risk for osteoporosis. As the excess calcium enters the bloodstream, this also causes serious risks.
Kidneys with poor function do not control the amount of fluid in the circulatory system. That has several physiological effects on the body. As excess fluid builds up in the bloodstream, it increases blood volume. Increased blood volume forces the heart to work harder to pump oxygen-rich blood to the organs and tissues. This leads to hypertension, or high blood pressure. High blood pressure increases the risk for diabetes, heart attack, stroke and hypertensive retinopathy, making it a serious condition that needs regular monitoring and treatment. As the amount of fluid in the bloodstream increases, sodium levels decrease. Since sodium plays a role in muscle contraction and the transmission of nerve impulses, this also has risks.
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The kidneys remove waste from the blood by filtering the wastes and excreting them in the urine. As kidney function declines, the kidneys do not filter wastes properly, leading to an accumulation of waste products in the bloodstream. Two major waste products build up and cause some of the most common signs of renal failure. These waste products are blood urea nitrogen (BUN) and creatinine. The body produces creatinine as a byproduct of protein metabolism. As these waste products build up in the blood, it causes itching, fatigue and other symptoms.
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When the kidneys work properly, protein molecules stay in the bloodstream for use in the body. When kidney damage occurs, it allows protein to leak out of the kidneys and into the urine. In the early stages of renal failure, microalbumin leaks from the kidneys because it consists of small molecules. As kidney failure worsens, larger protein molecules leak into the urine. Laboratory tests will reveal low levels of albumin in the blood and high levels of microalbumin in the urine, along with protein in the urine.
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The Merck Manual for Healthcare Professionals: Chronic Kidney Disease (Chronic Renal Failure)
eMedicine from WebMD: Hyperphosphatemia
Loyola University Chicago: Chronic Renal Failure