Kidney failure occurs when the kidney lose their ability to filter waste from the bloodstream. It can be developed suddenly (acute) or over the long term (chronic).
Many conditions, diseases and medicines can create situations that lead to acute or chronic kidney disease.
Acute kidney injury (acute renal failure)
- Acute kidney failure is the sudden loss of the kidney’s function over the course of a few hours or days. The kidneys are unable to remove wastes and excess fluids, which then buildup in the body and upset the body’s normal chemical balance. Acute kidney injury is more commonly reversible than chronic kidney failure.
- Symptoms depend on the cause but may include fluid buildup in the legs, ankles and feet or electrolyte imbalance, little or no urine output, pain just below the rib cage, dizziness upon standing, loss of appetite, nausea or vomiting.
- There may be an obstruction in the urinary tract that is blocking the flow of urine out of the body and causes pain in the side or lower back, blood in the urine or reduced urine output. Tumors, kidney stones or an enlarged prostate can block the flow of urine in the urinary tract. A blockage in the renal artery cuts off the supply of oxygen to the kidneys, and kidneys need oxygen to function.
- Dehydration may cause increased thirst, lightheadedness or faintness, a weak and rapid pulse.
- Many people with acute kidney injury are already hospitalized, particularly critically ill people who need intensive care such as those with burns, shock, drug toxicity, kidney infection, sepsis, trauma and severe diarrhea may be at greater risk for acute kidney failure.
- A buildup of waste products indicates loss of kidney function and tests will show an increase in creatinine and blood urea nitrogen (BUN) levels.
Chronic kidney disease
Chronic kidney disease is also called chronic renal failure or chronic renal insufficiency.
Chronic kidney disease is caused by damage to the kidneys. In chronic kidney disease the kidneys are no longer able to clean toxins and waste product from the blood and perform their functions to full capacity. The kidneys do not usually fail all at once. Instead, kidney disease progresses slowly over a period of years.
When the disease gets worse and wastes have built up in the blood, you could have kidney failure.
The most common causes of this damage are:
- Uncontrolled high blood pressure over many years
- High blood sugar over many years – this happens in uncontrolled type 1 or type 2 diabetes
Other things that can lead to chronic kidney disease include:
- Kidney diseases and infections, such as polycystic kidney disease and glomerulonephritis, or a kidney problem you were born with.
- Symptoms may not develop until there is very little kidney function left.
- Other problems such as anemia and increased levels of phosphates in the blood develop as chronic kidney disease progresses.
There are five stages of chronic kidney disease, with stages 4 and 5 leading to kidney failure
Glomerular filtration rate (GFR) is the best measure of kidney function. The GFR is the number used to figure out a person’s stage of kidney disease. A math formula using the person’s age, race, gender and their serum creatinine is used to calculate a GFR. A doctor will order a blood test to measure the serum creatinine level. When kidneys are working well they remove creatinine from the blood. As kidney function slows, blood levels of creatinine rise:
- Stage 1 is normal kidney function; GFR is > 90
- Stage 2 indicates Mild CKD; GFR = 60–89
- Stage 3A indicates Moderate CKD; GFR is 45–59
- Stage 3B is Moderate CKD; GFR is 30–44
- Stage 4 indicates Severe CKD; GFR is 15–29
- Stage 5 indicates End Stage CKD; GFR is < 15
Dialysis or a kidney transplant is needed in order to maintain health at stage 5.