In chronic renal failure (CRF), the kidney function decreases gradually but progressively over time. This condition can lead to end-stage renal disease in some patients and is mostly caused by underlying chronic kidney disease (CKD). Some forms of CRF run in families. Symptoms of CRF usually only develop when 60 to 70% of kidney function is already lost.
What is chronic renal failure?
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. The loss of kidney cells causes a decrease in the production of crucial hormones and enzymes. One of the most consistent findings in a patient with CRF is insufficient red blood cells or anaemia.
How the disease progresses
CRF is a progressive condition where renal function can decline until it results in end-stage renal failure. At this stage it is not possible to sustain life 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
It has been estimated that 10% of the world’s population has some degree of CKD. From this statistic, it is believed that around five million South Africans older than age 20 years have CKD, with the figure in black South Africans almost certainly being higher, according to an article in the February 2015 issue of the South African Medical Journal (SAMJ).
What is significant in South Africa is that we have very high prevalence rates of three important diseases that put people at risk of CKD, i.e. hypertension, type 2 diabetes mellitus and HIV. While some risk factors like age, male sex and hereditary kidney disease cannot be controlled, others like diabetes and hypertension 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.
Chronic diseases, especially diabetes and primary 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. Lifestyle and dietary habits play a large role in the increasing incidence of hypertension (high blood pressure) and diabetes in western society as well as developing countries.
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 is therefore important to keep in mind.
Long-term exposure to certain drugs, e.g. painkillers and toxins including lead and mercury can also lead to CRF. Further deterioration of kidney function can be prevented by avoiding such exposure.
Symptoms and signs
Because the kidneys play such an important role in ensuring the optimal function of the body’s cells, every organ in the body is affected when they fail. However, the body can function even if the kidneys are not working optimally or if there is only one kidney.
CRF develops over varying periods of time e.g. days, weeks to years. Symptoms appear late in the course of the disease and are often non-specific like increased fatigue and lethargy. Early symptoms can include
- insomnia (sleep problems)
- increased urination at night
Symptoms of advanced kidney failure include:
- shortness of breath with exertion
- nausea and vomiting
- loss of appetite
- skin that may become itchy, pale or yellow
- As renal failure worsens, confusion and seizures can occur.
The aetiology of CKD cannot always be easily determined and it is important to take a detailed history combined with a thorough clinical examination. It is often necessary to include examination of both structure (renal ultrasound) and function (estimated GFR (eGFR)) of the kidneys in the evaluation.
CKD often presents as a urinary abnormality in the face of normal renal function that CKD is usually asymptomatic, this concept becomes very important in alerting the doctor that his/her patient has a serious kidney disorder that needs correct diagnosis and management
- More severe symptoms start to appear when kidney function is less than 10% (or less than 15% in diabetic patients). These symptoms 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.
Kidney function is measured by establishing how well waste is filtered from the blood using a test called the GFR or glomerular filtration rate. It can also be used to predict outcome of the disease.
- As kidney function declines, it can cause a dangerous chemical imbalance and also lead to bleeding and a renal bone disease called renal osteodystrophy.
- Anaemia, or a decline in the oxygen-carrying red blood cells, is commonly found in CRF. This occurs because the kidneys are unable to produce sufficient erythropoietin, a 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.
General practitioners (GPs) generally find renal disease difficult to diagnose, understand and treat. For example, chronic kidney disease (CKD) is often not recognised because it has no specific symptoms, and is either not diagnosed or only diagnosed at an advanced stage.
The most useful indication of a diagnosis of any stage of chronic kidney disease is the presence of either hypertension (high blood pressure), urinary dipstick abnormality or both. If your doctor detects abnormalities in your blood pressure or urine dipstick test, he/she should refer you to a nephrologist or specialist physician who is best qualified to deal with kidney disease including CRF.
If you have a chronic condition that is known to cause kidney damage, it is important to be monitored by blood pressure checks, urine dipstick tests and eGFR tests, as symptoms typically occur late in the disease.
Early diagnosis of chronic kidney disease and early referral to a nephrologist or nephrology centre to identify any preventable or potentially reversible causes is essential for adequate management.
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. Note, however, that drugs cannot reverse kidney failure.Important measures to prevent deterioration of kidney function also include aspects such as making changes in lifestyle and diet. Dietary changes are important and will focus on limiting foods containing phosphate and potassium.
Medications that bind phosphates are prescribed during meals to help control the calcium–phosphate imbalance found in CRF and to prevent renal bone disease.
Patients with diabetes or hypertension must strive for optimal control of blood sugar and blood pressure. 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.
Other 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.
As anaemia is common in CRF, your specialist may prescribe erythropoietin therapy, which is often combined with iron and sometimes with folic acid and certain vitamins. Erythropoietin is a glycoprotein hormone that controls red blood cell production. If erythropoietin therapy is started before end-stage renal failure occurs, it may delay the need for dialysis.
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. This medication is now used whenever the diagnosis of CRF is made provided the patient can tolerate the drugs.
Dialysis may need to be considered when renal function is severely impaired and the patient is symptomatic.
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Reviewed and revised by Professor A M Meyers,MBBCh, FCP (SA), Cert Nephrology (SA), FRCP (London), Donald Gordon Medical Centre, Klerksdorp Hospital, and National Kidney Foundation of South Africa, March 2015.
Originally written by Dr K. Coetzee, reviewed by Dr R.Moosa,TygerbergAcademic Hospital