This occurs when the renal reserve is lost and there is irreversible damage of nephrons. Onset is usually slow and asymptomatic,progressing over several years. The main causes are diabetes mellitus,glomerulonephritis and hypertension.
The effects on glomerular filtration rate,selective reabsorption and tubular secretion are significant. GFR and filtrate volumes are greatly reduced,and reabsorption of water is seriously impaired. This results to high production of urine. Reduced glomerular filtration leads to accumulation of waste substances in the blood,notably urea and creatinine. When renal failure becomes evident,blood urea levels are raised (uraemia). Some signs and symptoms are nausea,vomiting,gastrointestinal bleeding,anaemia and Pruritis.
Others are:
- Polyuria. Large volumes of dilute urine are passed,because water reabsorption is impaired.
- Acidosis. As the kidney buffer system that normally controls the PH of the body fluids fails,hydrogen ions accumulate.
- Electrolyte imbalance. This is also as a result of impaired tubular reabsorption and secretions.
- Anaemia. Deficiency of erythropoietin occurs after a few months,causing anaemia that is usually exacerbated by haemodialysis which damages red blood cells.
