CHRONIC KIDNEY DISEASE OVERVIEWChronic kidney disease (CKD, also called kidney failure or renal failure) is a condition in which the kidneys lose some of their ability to remove waste products and excess fluid from the bloodstream. As waste products and fluids build up in the body, other body systems are affected, which can be harmful to your health.

The most common causes of CKD are diabetes and high blood pressure. In the early stages of CKD, there are no symptoms. The disease can progress to complete kidney failure, also called end-stage kidney disease. This occurs when kidney function has worsened to the point that dialysis or kidney transplantation is required to maintain good health and even life, which is typically when kidney function is approximately 10 percent or less of the normal kidney function.

The main goal of treatment is to prevent progression of CKD to complete kidney failure. The best way to do this is to diagnose CKD early and control the underlying cause.

The symptoms, evaluation, and management of CKD will be reviewed here. Kidney transplantation, peritoneal dialysis, and hemodialysis are discussed separately.

NORMAL KIDNEY FUNCTIONA brief overview of normal kidney function can help in the understanding of CKD. The kidneys function to remove wastes and excess water from the blood. These wastes and fluids are combined to form urine .Many vital body functions are dependent upon the proper functioning of the kidneys. The kidneys also control the amount of sodium, potassium, phosphorous, calcium, and other chemicals in the body.

In order for this filtering process to occur properly, the blood pressure and blood flow to the kidneys must be adequate. If the arteries leading to the kidney are diseased, the filtering process will be affected. Filtering of the blood is done in the kidney by structures called "nephrons." The nephrons , including the glomeruli and the tubules, must be healthy, and the path from the nephron to the urethra must not be blocked. There are normally approximately 700 thousand to 1 million filtering units or nephrons in each kidney. Diseases that reduce the number of normally functioning nephrons and/or reduce the function of nephrons cause CKD over time.

When the kidney filters are working properly, the result is a proper balance of fluids and chemicals in the body. If an imbalance occurs, many critical bodily functions can be affected, possibly producing symptoms associated with kidney disease.

CHRONIC KIDNEY DISEASE RISK FACTORSA number of factors can increase the risk of developing CKD, including:

●Diabetes mellitus

●High blood pressure

●A family history of kidney disease

●Obesity

●Smoking

●Older age

●Having protein in the urine

●Having autoimmune diseases such as lupus

●Being from a Black population or belonging to certain other underrepresented groups

CHRONIC KIDNEY DISEASE COMPLICATIONSMost people with CKD do not have symptoms until the kidney function is at least moderately to severely impaired. CKD is often discovered when blood or urine tests done for other reasons show one or more of the abnormalities discussed above. The blood test that is most commonly used to check the level of kidney function is the creatinine concentration. As kidney function goes down, the creatinine concentration in the blood goes up. The most common urine tests are for protein or albumin in the urine. Sometimes, people with CKD will develop swelling, most commonly around the feet and ankles, before any other symptoms appear.

Even when kidney failure is advanced, most people still make a normal or near-normal amount of urine; this is sometimes confusing. Urine is being formed, but it does not contain sufficient amounts of the body's waste products.

With advanced kidney disease, you may develop edema (swelling of the feet, ankles, or legs), loss of appetite, increased sleepiness, nausea, vomiting, confusion, and difficulty thinking. Patients often develop high blood pressure, blood chemistry (electrolyte) abnormalities such as a high potassium concentration, anemia (a decrease in red blood cells, which can cause fatigue and other symptoms), and bone disease.

Uremia — People with advanced kidney failure may develop a group of symptoms referred to as uremia. The symptoms of uremia include loss of appetite, nausea, vomiting, a build-up of fluid around the heart, nerve problems, and changes in mental status, including drowsiness, seizures, or coma.

EVALUATION AND DIAGNOSISA health care provider may use several tests to diagnose CKD and determine if there is a treatable underlying cause. These include the following:

Kidney function tests — The glomerular filtration rate (GFR) gives an approximate measure of the overall filtering abilities of the kidneys. Measuring true (actual) GFR is difficult and not practical in the care of most patients. Instead, GFR is usually estimated. The most common way to estimate GFR in adults is by measuring the creatinine level in the blood stream and then using this number in a formula to calculate an estimated GFR (eGFR) level.

The eGFR level is often shown on routine blood chemistry lab reports that your doctor obtains, and it is used for monitoring of kidney function impairment. The eGFR gives an estimate of kidney function, but actual kidney function can be higher or lower than this estimate. A measure of kidney function can also be obtained by collecting a 24-hour urine sample and measuring the concentration of creatinine (and sometimes urea) in the blood and urine. The blood urea nitrogen level is also commonly measured with blood tests and, like the blood creatinine concentration, generally goes up as kidney function declines.

●A reduction in GFR implies either worsening of the underlying kidney disease or the development of another, occasionally reversible kidney problem.

●An increase in GFR, on the other hand, indicates improvement in kidney function.

●A stable GFR in people with CKD implies stable disease.

Urine tests — The presence of albumin or protein in the urine (called albuminuria or proteinuria) is a marker of kidney disease. Even small amounts of albumin in the urine may be an early sign of CKD in some people, particularly those with diabetes and high blood pressure.

Imaging studies — Imaging tests (such as computed tomography [CT] or ultrasound) may be recommended to determine if there are any obstructions (blockages) of the urinary tract, kidney stones, or other abnormalities, such as many large cysts seen in a genetic disease called polycystic kidney disease.

Kidney biopsy — With a kidney biopsy, a small piece of kidney tissue is removed and examined under a microscope. The biopsy helps to identify abnormalities in kidney tissue that may be the cause of kidney diseases.

CHRONIC KIDNEY DISEASE TREATMENTThe first step in the treatment of CKD is to determine the underlying cause. Some causes are reversible, including use of medications that impair kidney function, blockage in the urinary tract, or decreased blood flow to the kidneys. Treatment of reversible causes may prevent CKD from worsening.

Research has shown that management of CKD is best done with the assistance of a nephrologist, a doctor who specializes in kidney diseases. Early referral to a nephrologist decreases the chance of developing complications associated with CKD.

Hypertension — Hypertension, or high blood pressure, is present in 80 to 85 percent of people with CKD. Maintaining good blood pressure control is the most important goal for trying to slow the progression of CKD. Taking a medication called an angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) reduces blood pressure and levels of protein in the urine and is thought to slow the progression of CKD to a greater extent than some of the other medicines used to treat high blood pressure. Newer medications have also become available in recent years that work with ACE inhibitors or ARBs to slow the progression of CKD.

Sometimes, a diuretic (water pill) or other medication is also added. You may be asked to monitor your blood pressure at home to be sure that your blood pressure is well controlled.

Anemia — People with CKD are at risk for anemia. This occurs because improperly functioning kidneys produce reduced amounts of a substance called erythropoietin. Anemia can lead to fatigue and other complications.

Selected patients can be treated with drugs that stimulate production of red blood cells. You or a family member may be able to inject these drugs at home. In some cases, iron supplements are also prescribed.

Dietary changes — Changes in your diet may be recommended to control or prevent some of the complications of CKD; most important is salt restriction to help control the blood pressure.

Protein — Restricting protein in the diet may slow the progression of CKD, although it is not clear if the benefits of protein restriction are worth the difficulty of sticking to a low-protein diet, particularly when other medications to slow progression of CKD are used. Although a reduced-protein diet may delay dialysis for several years, the unappetizing nature of the diet is difficult for most people to tolerate. Speak to your health care provider about the advantages and disadvantages of a low-protein diet. Some people may benefit from a plant-based diet.

Potassium — Some people with CKD develop a high blood potassium level, which can interfere with normal cell function. This is frequently treated with a diuretic that helps rid the body of excess potassium in the urine or a binder medication that helps rid the body of excess potassium in the bowel movements. Measures to prevent high potassium might also be recommended, including a low-potassium diet and avoiding medicines that raise potassium levels.

Phosphate — Phosphate is a mineral that helps to keep the bones healthy. Early in the course of CKD, the body begins to retain phosphate. As the disease progresses, high blood phosphate levels may develop. This is usually treated with medicines that prevent phosphate (found in foods) from being absorbed in the digestive tract. Dietary phosphate restrictions are also recommended

Cholesterol and triglycerides — High cholesterol and triglyceride levels are common in people with kidney disease. High triglycerides have been associated with an increased risk of coronary artery disease, which can lead to heart attack.

Treatments to reduce the risk of coronary artery disease are usually recommended, including dietary changes, medications for high triglyceride and cholesterol levels, stopping smoking, and tight blood sugar control in people with diabetes.

Sexual function — Men and women with advanced CKD often have difficulties with sexual function and infertility. Over 50 percent of men with end-stage kidney disease have difficulties with erection and decreased sex drive. Women often have disturbances in the menstrual cycle and fertility, usually leading to a stop in menstrual periods. Decreased sex drive may also occur in women.

You should discuss any changes in your sexual function with your health care provider because medications or other treatments may be effective.

Pregnancy — The risk that pregnancy will worsen kidney function or that decreased kidney function will interfere with pregnancy depends upon a number of factors. A woman with mild to moderate CKD who is considering becoming pregnant should discuss the possible risks with her nephrologist and obstetrical provider before trying to conceive.

Women with end-stage kidney disease who are on dialysis and who become pregnant are at increased risk for miscarriage, premature delivery, severe hypertension, and preeclampsia. A woman who undergoes successful kidney transplantation has a lower risk of these complications. It may be advantageous for a woman to delay becoming pregnant while on hemodialysis if kidney transplantation in the near future is likely. Hemodialysis may need to be done six to seven times per week during pregnancy.

PREPARING FOR DIALYSISSome people with CKD progressively worsen over time and will eventually need to consider starting dialysis or getting a kidney transplant. There are two types of dialysis: hemodialysis and peritoneal dialysis. Some patients may also choose not to start dialysis when it is unlikely to extend their life.

Kidney transplantation is also an option for some people with CKD even before ever starting dialysis. Patients should talk with their doctors about getting an evaluation for a kidney transplant long before they are getting close to needing dialysis.

An important component of treatment for patients with CKD is planning for dialysis in advance. Although kidney transplantation is the treatment of choice in most cases, many people must wait months or years for a kidney to become available. Dialysis will likely be needed, often for an extended period.

Dialysis and kidney transplantation are discussed in detail separately.