Due to its important and diverse function in maintaining homeostasis, the kidney is a very important organ inside our body. Chronic renal failure is manifested by many clinical symptoms, mostly biochemical in origin. The two kidneys are the site of urine formation. The urine of humans is usually composed of water and the molecule urea. Under pathological situations this structre of the urine is altered and can include also other substances such as proteins. A condition that is called proteinurea. Medically it is called the nephrotic syndrome.
The kidney functions by filtering the blood from the waste products such as metabolized medications.
One of the many functions of the kidney is the synthesis of erythropoietin. Erythropoietin is a hormone that is necessary for the formation of red blood cells. In chronic renal failure, the synthesis of this hormone is impaired. Therefore one of the clinical symptoms of chronic renal failure is anemia due to the shortage or deficiency of red blood cells. Red blood cells synthesis is stimulated by testosterone, therefore anemia due to chronic renal failure is less manifested in men than in women.
Another function of the kidney is the synthesis of vitamin D. Vitamin D is important for the metabolism of bone tissues. It increases the absorption of calcium ions in the intestine. Thus contributing to calcium homeostasis. A deficiency of vatamin D means the formation of hypocalcemia. Shortage of vitamin D is manifested as osteomalacia in adults and rickets in children.
In normal kidney function, electrolytes balance in the blood is carefully monitored, and is kept within a narrow range. In renal failure this electrolytes balance in disrupted due to the inability of the kidney to rid itself from the excess of electrolytes that accumulate in the blood.
One of these accumulated products is creatinine in addition to urea. Creatinine is used in the clinical lab as a measure of kidney appropriate functioning. In chronic renal failure, levels of creatinine are elevated in addition to elevation of urea levels in the blood also. A condition that is called uremia.
Other electrolytes balance are also affected in chronic renal failure. Normally there is active transport of sodium and potassium in the cells of the kidney. In addition there is active reabsorption of these electrolytes in the renal tubules. This active transport uses that are called ATPase. In renal pathology the reabsorption process of these electrolytes is impaired. Therefore some of these electrolytes accumulate in the blood. Impotrant is especially the accumulation of potassium ions leading to kyperkalemia.
This condition is important clinically due to the importance of potassium in heart muscle contraction and nerve cells firing. Hyperkalemia can affect the heart muscle by causing arrythmia or heart arrest.
Another electrolytes that are affected also are phosphate and hyrogen ions. In chronic renal failure phosphate ions concentration in the blood is elevated. Thus contributing to hyperphosphatemia. In addition, due to the inability of the kidney to rid itself from the excess protons in the blood, acidosis results.