Patient information: Chronic kidney disease

CHRONIC KIDNEY DISEASE OVERVIEW

Chronic kidney disease (CKD, also called kidney failure) is a condition in which the kidneys lose the ability to remove waste and excess water from the bloodstream. As waste and fluids accumulate, other body systems are affected, potentially leading to complications.

The most common causes of chronic kidney disease are diabetes and high blood pressure. In the early stages of CKD, there are no obvious symptoms. The disease can progress to complete kidney failure, also called end stage renal disease. This occus when kidney function has worsened to the point that dialysis or kidney transplantation is required to maintain life.

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

The symptoms, evaluation, and management of chronic kidney disease will be reviewed here. Kidney transplantation, peritoneal dialysis, and hemodialysis are discussed separately. (See "Patient information: Dialysis or kidney transplantation — which is right for me?" and "Patient information: Hemodialysis".)

NORMAL KIDNEY FUNCTION

A brief overview of normal kidney function can help in the understanding of chronic kidney disease. The kidneys function to remove wastes and excess water from the blood. These wastes and fluids are combined to form urine (figure 1). Many vital body functions are dependent upon the proper functioning of the kidneys.

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. The nephrons (figure 2), including the glomeruli and the tubules, must be healthy, and the path from the nephron to the urethra (figure 3) must not be blocked.

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 (see 'Chronic kidney disease symptoms' below.

CHRONIC KIDNEY DISEASE RISK FACTORS

A number of disorders can increase the risk of developing chronic kidney disease, including:

• Diabetes mellitus
• High blood pressure
• Chronic glomerulonephritis (inflammation of the glomeruli, (see "Patient information: Glomerular disease overview")

• Polycystic kidney disease (cysts in the kidneys, (see "Patient information: Polycystic kidney disease".
• A family history of kidney disease

CHRONIC KIDNEY DISEASE SYMPTOMS

Most people with chronic kidney disease do not have symptoms until the kidney function is severely impaired. The problem is often discovered when blood or urine tests, done for other reasons, show one or more of the abnormalities discussed above.

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), high blood pressure, blood chemistry (electrolyte) abnormalities, anemia (a decrease in red blood cells, which can cause fatigue and other symptoms), and bone disease. (See "Patient information: Edema (swelling)".)

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, swelling around the heart, nerve problems, and changes in mental status, including drowsiness, seizures, or coma.

EVALUATION AND DIAGNOSIS

A healthcare provider may use several tests to diagnose chronic kidney disease 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 number of functioning nephrons. GFR is used to monitor the severity of kidney impairment. The most common way to estimate the GFR in adults is with several blood tests.

• 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 renal function.
• A stable GFR in people with chronic kidney disease implies stable disease.

Urine tests — Urine tests can give important information about kidney function. 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, called microalbuminuria, may be an early sign of chronic kidney disease in some people, particularly those with diabetes and high blood pressure. (See "Patient information: Protein in the urine (proteinuria)".)

Imaging studies — Imaging tests (such as CT or ultrasound) may be recommended to determine if there are any obstructions (blockages) of the urinary tract, kidney stones, or other abnormalities. (See "Patient information: Kidney stones in adults".)

Renal biopsy — In a renal biopsy, a small piece of kidney tissue is removed and analyzed. The biopsy helps to identify abnormalities in kidney tissue that may be the cause of renal failure. (See "Patient information: Renal (kidney) biopsy".)

CHRONIC KIDNEY DISEASE TREATMENT

The first step in the treatment of chronic kidney disease 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 chronic kidney disease 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 chronic kidney disease.

Hypertension — Hypertension, or high blood pressure, is present in 80 to 85 percent of people with chronic kidney disease. Maintaining good blood pressure control is the most important goal for trying to slow progression of CKD. Taking a medication called angiotensin converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs) reduce blood pressure and levels of protein in the urine, and can slow the progression of chronic kidney disease.

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. (See "Patient information: High blood pressure treatment in adults".)

Anemia — People with chronic kidney disease 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 can inject these drugs at home. In some cases, iron supplements are also prescribed. (See "Anemia of chronic kidney disease: Target hemoglobin/hematocrit for patients treated with erythropoietic agents".)

Dietary changes — Changes in your diet may be recommended to control or prevent some of the complications of chronic kidney disease

Protein restriction — Restricting protein in the diet may slow the progression of chronic kidney disease, although it is not clear if the benefits of protein restriction are worth the difficulty of sticking to a low protein diet. 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 healthcare provider about the advantages and disadvantages of a low protein diet. (See "Protein restriction and progression of chronic kidney disease".)

High potassium — Some people with chronic kidney disease develop a high blood potassium level, which can interfere with normal cell function. This is frequently treated with a diuretic. Measures to prevent high potassium might also be recommended, including a low potassium diet and avoiding medicines that raise potassium levels. (See "Patient information: Low potassium diet".)

High phosphate — Phosphate is a mineral that helps to keep the bones healthy. Early in the course of chronic kidney disease, the body begins to retain phosphate. As the disease progresses, high blood phosphate levels can 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 (figure 4A-B).

High 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. (See "Patient information: High cholesterol and lipids (hyperlipidemia)" and "Patient information: Smoking cessation" and "Patient information: Self-blood glucose monitoring in diabetes mellitus".)

Sexual function — Men and women with advanced chronic kidney disease 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 healthcare provider because medications or other treatments may be effective. (See "Patient information: Sexual problems in men" and "Patient information: Sexual problems in women".)

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 chronic kidney disease who is considering becoming pregnant should discuss the possible risks with her nephrologist and obstetrical provider before trying to conceive.

Pregnancy is not recommended for women with end-stage kidney disease due to the increased risk of miscarriage, premature delivery, worsened kidney function, and preeclampsia. A woman who undergoes successful renal transplantation has a reduced risk of these complications.

PREPARING FOR DIALYSIS

Some people with chronic kidney disease progressively worsen over time and will eventually need dialysis. There are two types of dialysis: hemodialysis and peritoneal dialysis. Kidney transplantation is also an option for some people with chronic kidney disease.

An important component of treatment for patients with chronic kidney disease 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. (See "Patient information: Dialysis or kidney transplantation — which is right for me?" and "Patient information: Hemodialysis" and "Patient information: Peritoneal dialysis".)

WHERE TO GET MORE INFORMATION

Your healthcare provider is the best source of information for questions and concerns related to your medical problem. Because no two people are exactly alike and recommendations can vary from one person to another, it is important to seek guidance from a provider who is familiar with your individual situation.

This discussion will be updated as needed every four months on our web site (www.uptodate.com/patients). Additional topics as well as selected discussions written for healthcare professionals are also available for those who would like more detailed information.

Some of the most pertinent include:

Patient Level Information:
Patient information: Dialysis or kidney transplantation — which is right for me?
Patient information: Hemodialysis
Patient information: Glomerular disease overview
Patient information: Polycystic kidney disease
Patient information: Edema (swelling)
Patient information: Protein in the urine (proteinuria)
Patient information: Kidney stones in adults
Patient information: Renal (kidney) biopsy
Patient information: High blood pressure treatment in adults
Patient information: Low potassium diet
Patient information: High cholesterol and lipids (hyperlipidemia)
Patient information: Smoking cessation
Patient information: Self-blood glucose monitoring in diabetes mellitus
Patient information: Sexual problems in men
Patient information: Sexual problems in women
Patient information: Peritoneal dialysis

Professional Level Information:
Anemia of chronic kidney disease: Target hemoglobin/hematocrit for patients treated with erythropoietic agents
Antihypertensive therapy and progression of nondiabetic chronic kidney disease
Assessment of nutritional status in end-stage renal disease
Bone biopsy and the diagnosis of renal osteodystrophy
Chronic kidney disease and coronary heart disease
Clinical manifestations and diagnosis of coronary heart disease in end-stage renal disease (dialysis)
Darbepoetin alfa for the management of anemia in chronic kidney disease
Diagnostic approach to the patient with acute or chronic kidney disease
Epidemiology of chronic kidney disease and screening recommendations
Erythropoietin for the anemia of chronic kidney disease among predialysis and peritoneal dialysis patients
Erythropoietin for the anemia of chronic kidney disease in hemodialysis patients
Erythropoietin: Subcutaneous administration
Hypertension following erythropoietin in chronic kidney disease
Indications for initiation of dialysis in chronic kidney disease
Management of secondary hyperparathyroidism and mineral metabolism abnormalities in adult predialysis patients with chronic kidney disease
Management of secondary hyperparathyroidism and mineral metabolism abnormalities in dialysis patients
Overview of the management of chronic kidney disease in adults
Protein restriction and progression of chronic kidney disease
Risk factors and epidemiology of coronary artery disease in end-stage renal disease (dialysis)
Secondary factors and progression of chronic kidney disease
Treatment of metabolic acidosis in chronic kidney disease
Urinalysis in the diagnosis of renal disease

A number of web sites have information about medical problems and treatments, although it can be difficult to know which sites are reputable. Information provided by the National Institutes of Health, national medical societies and some other well-established organizations are often reliable sources of information, although the frequency with which they are updated is variable.

• National Library of Medicine

      (www.nlm.nih.gov/medlineplus/healthtopics.html)

• National Institute of Diabetes and Digestive and Kidney Diseases

      (www.niddk.nih.gov)

• National Kidney Foundation

      (800) 922-9010
      (www.kidney.org)

• United Network for Organ Sharing (UNOS)

      (888) 894-6361
     (www.unos.org)

• American Kidney Fund

      (www.kidneyfund.org)

• American Association of Kidney Patients

      (www.aakp.org)

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