Renal failure or kidney failure is a situation in which the kidneys fail to function adequately. It is divided into acute and chronic forms; either form may be due to a large number of other medical problems.
Biochemically, it is typically detected by an elevated serum creatinine. In the science of physiology, renal failure is described as a decrease in the glomerular filtration rate. When the kidneys malfunction, problems frequently encountered are abnormal fluid levels in the body, deranged acid levels, abnormal levels of potassium, calcium, phosphate, hematuria (blood in the urine) and (in the longer term) anemia. Long-term kidney problems have significant repercussions on other diseases, such as cardiovascular disease.
Renal failure can broadly be divided into two categories: acute or chronic renal failure. The type of renal failure is determined by the trend in the serum creatinine. Other factors which may help differentiate acute and chronic kidney disease include the presence of anemia and the kidney size on ultrasound. Chronic kidney disease generally leads to anemia and small kidney size.
Acute renal failure
Acute renal failure (ARF) is a rapidly progressive loss of renal function, generally characterized by oliguria (decreased urine production, quantified as less than 400 mL per day in adults, less than 0.5 mL/kg/h in children or less than 1 mL/kg/h in infants); body water and body fluids disturbances; and electrolyte derangement. An underlying cause must be identified to arrest the progress, and dialysis may be necessary to bridge the time gap required for treating these fundamental causes. ARF can result from a large number of causes.
Chronic kidney disease
Stage 5 Chronic Kidney Disease (CKD) can develop slowly and show few initial symptoms, be the long term result of irreversible acute disease or be part of a disease progression.
Acute on chronic renal failure
Acute renal failure can be present on top of chronic renal failure. This is called acute-on-chronic renal failure (AoCRF). The acute part of AoCRF may be reversible and the aim of treatment, as with ARF, is to return the patient to their baseline renal function, which is typically measured by serum creatinine. AoCRF, like ARF, can be difficult to distinguish from chronic renal failure, if the patient has not been monitored by a physician and no baseline (i.e., past) blood work is available for comparison.
Symptoms of kidney disease can vary from person to person. Some people with kidney disease may not even feel sick, or they may not notice their symptoms. If the kidney function fails, the waste products accumulate in the blood and the body, termed azotaemia. Very mild levels of azotaemia may produce little or no symptoms, but if the kidney failure continues then symptoms will become noticeable. If the kidney (or renal) failure is of sufficient degree to cause symptoms. Renal failure accompanied with noticeable symptoms is termed uraemia.
Symptoms of kidney failure include:
- High levels of urea in the blood, which can result in:
- Vomiting and/or diarrhea, which may lead to dehydration
- Weight loss
- Nocturnal urination
- Foamy or bubbly urine
- More frequent urination, or in greater amounts than usual, with pale urine
- Less frequent urination, or in smaller amounts than usual, with dark coloured urine
- Blood in the urine
- Pressure, or difficulty urinating
- A build up of phosphates in the blood that diseased kidneys cannot filter out may cause:
- Bone damage
- Muscle cramps (caused by low levels of calcium which can cause hypocalcaemia)
- A build up of potassium in the blood that diseased kidneys cannot filter out (called hyperkalemia) may cause:
- Abnormal heart rhythms
- Muscle paralysis
- Failure of kidneys to remove excess fluid may cause:
- Swelling of the legs, ankles, feet, face and/or hands
- Shortness of breath due to extra fluid on the lungs (may also be caused by anemia)
- Polycystic kidney disease, which causes large, fluid-filled cysts on the kidneys and sometimes the liver, can cause:
- Pain in the back or side
- Healthy kidneys produce the hormone erythropoietin which stimulates the bone marrow to make oxygen-carrying red blood cells. As the kidneys fail they produce less erythropoietin resulting in less red blood cells being produced to replace the natural breakdown of old red blood cells. As a result the blood carries less haemoglobin, which is known as anemia. This can result in:
- Feeling tired and/or weak
- Memory problems
- Difficulty concentrating
- Low blood pressure
- Other symptoms include:
- Appetite loss, a bad taste in the mouth
- Difficulty sleeping
- Darkening of the skin
Causes of acute renal failure
Acute kidney failure usually occurs as the result of a sudden interruption in the blood supply to the kidney, or as a result of a toxic overload of the kidneys. Some causes of acute failure include accidents, injuries or complications from surgery where the kidneys are deprived of normal blood flow for an extended period of time. Heart-bypass surgery is an example of a situation in which the kidneys receive reduced blood flow.
Drug overdoses, whether accidental or from chemical overloads of drugs such as antibiotics or chemotherapy, may also cause the onset of acute kidney failure. Unlike in chronic kidney disease, however, the kidneys can often recover from acute failure, allowing the patient to resume a normal life. People suffering from acute failure require supportive treatment until their kidneys recover function, and they often remain at an increased risk of developing future kidney failure.
Causes of chronic kidney disease
There are many causes of CKD. The most common cause is diabetes mellitus. The second most common cause is long-standing, uncontrolled, hypertension. Polycystic kidney disease is also a well known cause of chronic kidney disease. The majority of people afflicted with polycystic kidney disease have a family history of the disease. Many other genetic illnesses also affect kidney function. Overuse of some common drugs, such as aspirin, ibuprofen, cocaine and acetaminophen can also cause chronic kidney damage.
Methods of Measurement for CKD
- Stages of kidney failure
Chronic kidney failure is measured in five stages, which are calculated using a patient’s GFR, or glomerular filtration rate. Stage 1 CKD is mildly diminished renal function, with few overt symptoms. Stages 2 and 3 need increasing levels of supportive care from their medical providers to slow and treat their renal dysfunction. Patients in stages 4 and 5 usually require preparation of the patient towards active treatment in order to survive.Stage 5 CKD is considered a severe illness and requires some form of renal replacement therapy (dialysis) or kidney transplant whenever feasible.
- Glomerular filtration rate
A normal GFR varies according to many factors, including sex, age, body size and ethnicity. Renal professionals consider the glomerular filtration rate (GFR) to be the best overall index of kidney function. The National Kidney Foundation offers an easy to use on-line GFR calculator. for anyone who is interested in knowing their glomerular filtration rate.(A serum creatinine level, a simple blood test, is needed to use the calculator).
Use of the term uremia
Before the advancement of modern medicine, renal failure was often referred to as uremic poisoning. Uremia was the term used to describe the contamination of the blood with urine. Starting around 1847, this term was used to describe reduced urine output, that was thought to be caused by the urine mixing with the blood instead of being voided through the urethra. The term uremia is now used to loosely describe the illness accompanying kidney failure