Chronic kidney disease (CKD) is a condition characterized by a gradual loss of kidney function over time.
What is chronic kidney disease (CKD)?
Chronic kidney disease occurs when a person suffers from permanent loss of kidney function. This happens gradually, usually from months to years.
Chronic kidney disease is divided into five stages of increasing severity (see below). The term “renal” refers to the kidney, so another name for kidney failure is “renal failure.” Mild kidney disease is often called renal insufficiency.
If kidney disease gets worse, high levels of waste can build up in your blood and make you feel sick. You may develop complications like high blood pressure, anemia (low blood count), weak bones, poor nutritional health and nerve damage. Also, kidney disease increases your risk of having heart and blood vessel disease.
These problems may happen slowly over a long period of time. Chronic kidney disease may be caused by diabetes, high blood pressure and other disorders. Early detection and treatment can often keep chronic kidney disease from getting worse. When the disease progresses, it may eventually lead to kidney failure, which requires dialysis or a kidney transplant to maintain life.
The Facts about Chronic Kidney Disease (CKD)
How common is Chronic Kidney Disease?
Chronic kidney disease is a growing health problem in the United States. A report by the Centers for Disease Control (CDC) determined that 16.8 percent of all adults over the age of 20 have chronic kidney disease. Thus, one in six individuals has kidney disease.
Anyone can get chronic kidney disease at any age. However, some people are more likely than others to develop it. If you have any of the following conditions, you are at a higher-than-normal risk of developing CKD and your kidney functions may need to be monitored regularly:
What causes CKD?
Although chronic kidney disease sometimes results from primary diseases of the kidneys themselves, the major causes are diabetes and high blood pressure.
What are the symptoms of CKD?
The kidneys are remarkable in their ability to compensate for problems in their function. That is why chronic kidney disease may progress without symptoms for a long time until only very minimal kidney function is left.
Because the kidneys perform so many functions for the body, kidney disease can affect the body in a large number of ways. Symptoms vary greatly. Several different body systems may be affected. Notably, most patients have no decrease in urine output even with very advanced chronic kidney disease. However, you may notice that you:
How Chronic Kidney Disease (CKD) Can Be Graded
GFR—glomerular filtration rate is the best test to measure your level of kidney function and determine your stage of chronic kidney disease as specified below. Your doctor can calculate it from the results of your blood creatinine test, your age, race, gender and other factors.
The earlier kidney disease is detected, the better the chance of slowing or stopping its progression.
Chronic Kidney Disease Diagnosis
Chronic kidney disease usually causes no symptoms in its early stages. Only lab tests can detect any developing problems. Anyone at increased risk for chronic kidney disease should be routinely tested for development of this disease.
Urinalysis: A lot can be learned by analyzing the urine. The first step in urinalysis is doing a dipstick test. The dipstick has reagents that check the urine for the presence of various normal and abnormal constituents including protein. Then, the urine is examined under a microscope to look for red and white blood cells and the presence of casts and crystals (solids).
Only minimal quantities of albumin (protein) are present in urine normally. Therefore, a positive result on a dipstick test is abnormal. A more sensitive test is a laboratory estimation of the urine albumin (protein) and creatinine in the urine. The ratio of albumin and creatinine in the urine provides a good estimate of daily (protein) excretion.
24-Hour urine tests:
This test requires you to collect all of your urine for 24 consecutive hours. The urine may be analyzed for protein and waste products (urea nitrogen and creatinine). The presence of protein in the urine indicates kidney damage. The amount of creatinine and urea excreted in the urine can be used to calculate the level of kidney function and the glomerular filtration rate (GFR).
Glomerular filtration rate (GFR):
The GFR is a standard means of expressing overall kidney function. As kidney disease progresses, GFR falls. The normal GFR is about 100-140 mL/min in men and 85-115 mL/min in women. It decreases in most people with age. The GFR may be calculated from the amount of waste products in the 24-hour urine test or by using special markers administered intravenously. An estimation of the GFR (eGFR) can be calculated from the patient’s routine blood tests. Patients are divided into five stages of chronic kidney disease based on their GFR.
Creatinine and Urea (BUN) in the blood:
Blood urea nitrogen and serum creatinine are the most commonly used blood tests to screen for and monitor renal disease. Creatinine is a product of normal muscle breakdown. Urea is the waste product of breakdown of protein. The level of these substances rises in the blood as kidney function worsens.
Estimated GFR (eGFR):
The laboratory or your physician may calculate an estimated GFR using the information from your blood work. It is important to be aware of your estimated GFR and stage of chronic kidney disease. Your physician uses this information to recommend additional testing and suggestions for management.
Electrolyte levels and acid-base balance:
Kidney dysfunction causes imbalances in electrolytes, especially potassium, phosphorus, and calcium. High potassium (hyperkalemia) is a particular concern. The acid-base balance of the blood is usually disrupted as well.
Decreased production of the active form of vitamin D can cause low levels of calcium in the blood. The inability to excrete phosphorus due to failing kidneys causes its levels in the blood to rise. Testicular or ovarian hormone levels may also be abnormal.
Blood cell counts:
Because kidney disease disrupts blood cell production and shortens the survival of red cells, the red blood cell count and hemoglobin may be low (anemia). Some patients may also have iron deficiency due to blood loss in their gastrointestinal system. Other nutritional deficiencies may also impair the production of red cells.
Ultrasound is often used in the diagnosis of kidney disease. An ultrasound is a noninvasive type of imaging test. In general, kidneys are shrunken in size in chronic kidney disease, although they may be normal or even large in size in cases caused by adult polycystic kidney disease, diabetic nephropathy, and amyloidosis. Ultrasound may also be used to diagnose the presence of urinary obstruction or kidney stones and also to assess the blood flow into the kidneys.
A sample of the kidney tissue (biopsy) is sometimes required in cases in which the cause of the kidney disease is unclear. Usually, a biopsy can be collected using local anesthesia by introducing a needle through the skin into the kidney. This is usually done as an outpatient procedure, though some institutions may require an overnight hospital stay. See more in kidney biopsy submenu on this website.