Kidney failure occurs when the kidneys lose their ability to
function. To treat kidney failure effectively, it is important to know whether
kidney disease has developed suddenly (acute) or over the long term (chronic).
Many conditions, diseases, and medicines can create situations that lead to
acute and chronic kidney disease. Acute kidney injury, also called acute renal failure, is more commonly
reversible than chronic kidney failure.
The presence or lack of symptoms may help your doctor determine
whether acute kidney injury or chronic kidney disease is present.
Symptoms of decreased kidney function, such as
fluid buildup or
electrolyte imbalance, are more likely to develop with
acute kidney injury, regardless of how long the kidney has been malfunctioning.
Symptoms may reflect the actual cause of the kidney problem.
An obstruction in the urinary tract may cause
pain in the side or lower back (flank pain), blood in the urine, or reduced
Dehydration may cause extreme thirst; lightheadedness
or faintness; a weak, rapid pulse; and other symptoms.
Symptoms of chronic kidney disease may not develop
until very little kidney function remains. Other problems may
develop with chronic kidney disease, such as
anemia and increased levels of phosphates in the blood
(hyperphosphatemia), along with complications caused by kidney failure. These
complications often do not develop until kidney disease has been present for
Most cases of acute kidney injury occur in people who are already in
the hospital for other reasons. In these people, acute kidney injury is usually
diagnosed when routine tests show a sudden increase in
blood urea nitrogen (BUN) levels. A buildup of these
waste products in the blood points to a loss of kidney function. Your doctor
will compare these levels to previous tests to find out if kidney disease is
acute or chronic.
ultrasound of the kidneys also may help determine
whether kidney problems are acute or chronic. Normal-sized kidneys may be
present in either condition, but when both kidneys are smaller than normal,
chronic kidney disease is usually the problem.