The National Kidney Foundation has established guidelines to group chronic renal failure into stages based on the severity of the disease. According to this system, there are five stages of chronic renal disease, numbered 1 through 5; the higher the number, the more severe the limitation in kidney function. Stage 4 represents severe chronic renal disease, which is associated with a number of signs that mirror the severity of the illness.
Severely Decreased Glomerular Filtration Rate
Glomerular filtration rate (GFR) is a measurement of kidney function. The test provides a quantitative estimate of the amount of blood processed by the kidney's filtering units (the glomeruli) each minute. Stage 4 chronic renal disease is defined as a GFR of 15 to 29 milliliters per minute. A normal GFR is 90 to 120 milliliters per minute. When the GFR falls below 15 milliliters per minute, kidney replacement therapy (dialysis) or transplantation becomes necessary.
High Blood Pressure
Hypertension is the most common complication of chronic renal failure, and most people with stage 4 chronic renal disease have high blood pressure. Fluid overload due to severely compromised kidney function is the primary cause. Medication and rigorous salt and water restriction usually are required to control this complication.
Proteinuria and Low Blood Protein
Blood contains a high concentration of circulating proteins. Normally, protein from the blood does not enter the urine. However, most people with stage 4 chronic renal disease spill protein in their urine, a condition known as proteinuria. The loss of protein in the urine may cause a total body protein deficiency. People with stage 4 chronic renal disease often have this complication. Low blood protein levels cause fluid to leak from the blood into the tissues. Thus, people with severe renal disease often have swelling (edema) in their extremities, especially the feet, ankles and lower legs.
Anemia
The kidneys manufacture a hormone called erythropoietin, which stimulates the production of red blood cells. People with chronic renal disease may not produce sufficient erythropoietin, which leads to anemia--too few red blood cells. Most people with stage 4 chronic renal disease are anemic because of their kidney disease.
High Blood Phosphate
As renal failure progresses, the kidneys are less able to filter and excrete excess phosphate from the diet. This leads to high blood phosphate levels, common in people with stage 4 chronic renal disease.
Low Blood Calcium
As blood phosphate rises, calcium absorption from the gut decreases, eventually leading to a low blood calcium level. This abnormality is common among people with stage 4 chronic renal disease.
Decreased Bone Density
The abnormalities in calcium and phosphate and other metabolic abnormalities frequently cause a loss of bone density, which can be seen on X-rays. The loss of bone density makes people with stage 4 and 5 chronic renal disease more susceptible to fractures. When fractures occur, they tend to heal slowly. Bone pain is common, even in the absence of fractures.
References
- "Harrison's Principles of Internal Medicine, 16th Edition"; Dennis L. Kasper, M.D., et al, Editors; 2004
- Merck Manual: Chronic Kidney Disease
- Edinburgh Renal Unit: Chronic Renal Failure and Its Progression
- Family Practice Notebook: Chronic Renal Failure
- National Institute of Diabetes and Digestive and Kidney Diseases: The Kidneys and How They Work
