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01 February 2008

Kidney failure - chronic

In chronic renal failure (CRF) the kidney function decreases gradually but progressively. It is a lifelong condition that can lead to end-stage renal disease in some patients.

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Summary

  • In chronic renal failure the kidney function decreases gradually and progressively
  • Symptoms appear late in the disease
  • Chronic diseases can damage the kidneys
  • Renal function can decline until end-stage renal failure is reached
  • Treatment of diabetes and hypertension can slow down kidney damage

What is chronic renal failure?

In chronic renal failure (CRF) the kidney function decreases gradually but progressively over time. It is a lifelong condition that can lead to end-stage renal disease in some patients. It is mostly caused by underlying chronic kidney disease, but some forms of chronic CRF run in families.

You can survive even if your kidneys are not functioning 100%, or with only one kidney. The patient usually develops symptoms only when 60 to 70 percent of kidney function is already lost. Kidney function is measured by how well waste is filtered from the blood. This test is called the GFR or glomerular filtration rate, and can be used to predict outcome.

In CRF excess waste products build up resulting in the so-called uremic syndrome, irrespective of the initial cause or injury. Excess fluid may cause or worsen hypertension, and chemical abnormalities can lead to renal bone disease. With the loss of kidney cells there is a decrease in the production of crucial hormones and enzymes. Insufficient red blood cells or anaemia is one of the most consistent findings in these patients.

What are the causes of CRF?

Chronic diseases, especially diabetes and hypertension can damage the kidneys. Both diseases can cause the initial insult to the kidney, or speed the progression of any existing renal failure. Controlling blood sugar and blood pressure is essential to delay further decline in renal function. The incidence of high blood pressure and diabetes are on the increase in western society as well as developing countries due to lifestyle and dietary habits.

Certain kidney diseases like glomerulonephritis and pyelonephritis can become chronic inflammatory conditions that destroy kidney cells. Obstruction in the urinary tract is a potentially reversible cause of CRF and therefore important to keep in mind.

Long-term exposure to certain drugs, e.g. painkillers and toxins can also lead to CRF, including lead and mercury. Avoiding these can help prevent further deterioration of kidney function.

What are the symptoms and signs of CRF?

CRF develops over time and the body can function even if the kidneys are not working optimally. Symptoms appear late in the course of the disease and are often non-specific like increased fatigue and lethargy. The kidneys play such an important role in ensuring the optimal function of the body’s cells. When they fail every organ in the body is affected.

Insomnia (sleep problems) and increased urination at night can be early symptoms. Symptoms include shortness of breath with exertion, nausea, vomiting and loss of appetite. Skin can become itchy, pale or yellow. Hiccups can be a late sign, while confusion and seizures can occur as renal failure worsens.

Complications of CRF

When kidney function is less than 10 percent (or less than 15 percent in diabetic patients), more severe symptoms start to appear. These are usually caused by the high blood levels of waste products of which the markers are urea and creatinine. The so-called uremic syndrome can affect all the major organs of the body including the brain and may lead to uremic coma.

As kidney function declines, the chemical imbalance can be dangerous and also lead to a renal bone disease called renal osteodystrophy. Anaemia, or a decline in the oxygen-carrying red blood cells is a common finding in CRF. The kidneys are not able to produce enough erythopoietin, the hormone that stimulates bone marrow to make blood cells.

Maintaining fluid and salt balance becomes difficult and fluid can build up in the lungs and tissues of the body.

Diagnosis

Patients with chronic conditions that are known to cause kidney damage should be monitored for symptoms or signs of renal decline. Regular examinations, blood pressure checks, urine and blood tests can be done. Symptoms typically occur late in the disease and CRF is confirmed with blood tests. Special X-ray and ultrasound tests are also done and small, scarred kidneys are a common finding.

Treatment of CRF

Any preventable or potentially reversible causes must be identified. This may include obstruction, infection and use of nephrotoxic drugs. Patients with diabetes or hypertension must strive for optimal control of blood sugar and blood pressure. The aim of treatment is to preserve as much kidney function as possible, and delay progression of kidney failure. This is done by treating the underlying cause and complications of renal failure, often with medication. However, drugs cannot reverse kidney failure.

Drugs are used to control diabetes and hypertension. Certain anti-hypertensives can slow down kidney damage especially in diabetics. Drugs are also helpful to correct fluid and electrolyte imbalances.

Important steps to prevent deterioration of kidney function are to relieve any obstruction, stop nephrotoxic drugs, treat infection, control blood pressure and reverse dehydration if present.

Anaemia is common in CRF and erythropoietin therapy can be used, often combined with iron, and sometimes with folic acid and certain vitamins. If erythropoietin therapy is started before end-stage renal failure occurs, it may delay the need for dialysis.

Dietary changes are important with the emphasis being on the limitation of phosphate and potassium containing foods. Medications that bind phosphates are prescribed during meals. This is to help control the calcium–phosphate imbalance found in CRF and to prevent renal bone disease. When renal function is severely impaired and the patient is symptomatic, dialysis is considered.

The use of a special group of antihypertensive drugs called the angiotensin converting enzyme inhibitors (ACEI) has been shown to reduce the rate of decline of kidney function and is now used whenever the diagnosis of CRF is made provided the patient can tolerate the drugs.

Course of the disease

CRF is a progressive condition where renal function can decline until end-stage renal failure is reached. At this stage life cannot be sustained without dialysis or a kidney transplant. The rate of deterioration differs from patient to patient and not everyone develops end-stage renal disease.

Incidence and people at risk

Some risk factors cannot be controlled like age, male sex and hereditary kidney disease. Others like diabetes and high blood pressure can be treated and may slow down or prevent kidney damage. Risk factors for patients who already have CRF include hypertension, diabetes, a high-protein diet and high blood fats like cholesterol and triglycerides. These patients should also avoid analgesics and anti-inflammatory drugs.

Written by Dr K. Coetzee, reviewed by Dr R. Moosa, head of the Renal Unit, Tygerberg Academic Hospital.

 
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