Renal failure or kidney failure (formerly called renal insufficiency) describes a medical condition in which the kidneys fail to adequately filter toxins and waste products from the blood.
The two forms are acute (acute kidney injury) and chronic (chronic kidney disease); a number of other diseases or health problems may cause either form of renal failure to occur.
Renal failure is described as a decrease in the glomerular filtration rate. Biochemically, renal failure is typically detected by an elevated serum creatininelevel. Problems frequently encountered in kidney malfunction include abnormal fluid levels in the body, deranged acid levels, abnormal levels of potassium, calcium, phosphate, and (in the longer term) anemia as well as delayed healing in broken bones.
Depending on the cause, hematuria (blood loss in the urine) and proteinuria (protein loss in the urine) may occur. Long-term kidney problems have significant repercussions on other diseases, such ascardiovascular disease.
In the beginning, kidney failure may be asymptomatic (not producing any symptoms). As kidney function decreases, the symptoms are related to the inability to regulate water and electrolyte balances, to clear waste products from the body, and to promote red blood cell production.
Lethargy, weakness, shortness of breath, and generalized swelling may occur. Unrecognized or untreated, life-threatening circumstances can develop.
Metabolic acidosis, or increased acidity of the body due to the inability to manufacture bicarbonate, will alter enzyme and oxygen metabolism, causing organ failure.
Inability to excrete potassium and rising potassium levels in the serum (hyperkalemia) is associated with fatal heart rhythm disturbances (arrhythmias) including ventricular tachycardia and ventricular fibrillation.
Rising urea levels in the blood (uremia) can affect the function of a variety of organs ranging from the brain (encephalopathy) with alteration of thinking, to inflammation of the heart lining (pericarditis), to decreased muscle function because of low calcium levels (hypocalcemia).
Generalized weakness may be due to anemia, a decreased red blood cell count, because lower levels of erythropoietin produced by failing kidneys do not adequately stimulate the bone marrow. A decrease in red cells equals a decrease in oxygen-carrying capacity of the blood, resulting in decreased oxygen delivery to cells for them to do work; therefore, the body tires quickly.
As well, with less oxygen, cells more readily use anaerobic metabolism (an=without + aerobic=oxygen) leading to increased amounts of acid production that cannot be addressed by the already failing kidneys.
As waste products build in the blood, loss of appetite, lethargy, and fatigue become apparent. This will progress to the point where mental function will decrease and coma may occur.
Because the kidneys cannot address the rising acid load in the body, breathing becomes more rapid as the lungs try to buffer the acidity by blowing off carbon dioxide. Blood pressure may rise because of the excess fluid, and this fluid can be deposited in the lungs, causingcongestive heart failure.
Kidney failure can occur from an acute situation or from chronic problems.
In acute renal failure, kidney function is lost rapidly and can occur from a variety of insults to the body. The list of causes is often categorized based on where the injury has occurred.
Prerenal causes (pre=before + renal=kidney) causes are due to decreased blood supply to the kidney.
Examples of prerenal causes of kidney failure are:
- hypovolemia (low blood volume) due to blood loss;
- dehydration from loss of body fluid (for example, vomiting, diarrhea, sweating, fever);
- poor intake of fluids;
- medication, for example, diuretics ("water pills") may cause excessive water loss;
- abnormal blood flow to and from the kidney due to obstruction of the renal artery or vein.
Renal causes of kidney failure (damage directly to the kidney itself) include:
The body's immune system is overwhelmed from infection and causes inflammation and shutdown of the kidneys. This usually does not occur with urinary tract infections.
Some medications are toxic to the kidney, includingnonsteroidal anti-inflammatory drugs like ibuprofen and naproxen. Others potentially toxic medications include antibiotics like aminoglycosides [gentamicin (Garamycin), tobramycin], lithium (Eskalith, Lithobid), iodine-containing medications such as those injected for radiology dye studies.
This is a situation in which there is significant muscle breakdown in the body, and the damaged muscle fibers clog the filtering system of the kidneys. This can occur because of trauma, crush injuries, and burns. Some medications used to treat high cholesterolcan cause rhabdomyolysis.
Acute glomerulonephritis or inflammation of the glomeruli, the filtering system of the kidneys. Many diseases can cause this inflammation including systemic lupus erythematosus, Wegener's granulomatosis, and Goodpasture syndrome.
Post renal causes of kidney failure (post=after + renal= kidney) are due to factors that affect outflow of the urine:
Obstruction of the bladder or the ureters can cause back pressure because the kidneys continue to produce urine, but the obstruction acts like a dam, and urine backs up into the kidneys. When the pressure increases high enough, the kidneys are damaged and shut down.
Prostatic hypertrophy or prostate cancer may block the urethra and prevents the bladder from emptying.
Tumors in the abdomen that surround and obstruct the ureters.
Kidney stones. Usually, kidney stones affect only one kidney and do not cause kidney failure. However, if there is only one kidney present, a kidney stone may cause the lone kidney to fail.
Chronic renal failure develops over months and years.
The most common causes of chronic renal failure are related to:
- poorly controlled diabetes,
- poorly controlled high blood pressure,
- chronic glomerulonephritis.
Less common causes of chronic renal failure include:
- polycystic kidney disease,
- reflux nephropathy,
- kidney stones,
- prostate disease.
Prevention is always the goal with kidney failure. Chronic diseases such as hypertension and diabetes are devastating because of the damage that they can do to kidneys and other organs.
Lifelong diligence is important in keeping blood sugar and blood pressure within normal limits. Specific treatments are dependent upon the underlying diseases.
Once kidney failure is present, the goal is to prevent further deterioration of renal function. If ignored, the kidneys will progress to complete failure, but if underlying illnesses are addressed and treated aggressively, kidney function can be preserved, though not always improved.