Renal failure describes a medical condition in which the renal fail to adequately filter toxins and waste products from the blood.The renal play key roles in body function, not only by filtering the blood and getting rid of waste products, but also by balancing levels of electrolyte levels in the body, controlling blood pressure, and stimulating the production of red blood cells. Renals are located in the abdomen toward the back, normally one on each side of the spine. They get their blood supply through the renal arteries directly from the aorta and send blood back to the heart via the renal veins to the vena cava. When there is abnormality or damage occur to the kidney, it is called renal failure.In definition, renal failure is partial or complete loss of renal function. Renal 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 are due to decreased blood supply to the kidney.
Prerenal causes of renal 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; and
- 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:
- Sepsis: 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.
- Medications: Some medications are toxic to the kidney, including nonsteroidal 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.
- Rhabdomyolysis: 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 cholesterol can cause rhabdomyolysis.
- Multiple myeloma
- 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 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, and
- chronic glomerulonephritis.
Less common causes of chronic renal failure include:
- polycystic kidney disease,
- reflux nephropathy,
- kidney stones, and
- prostate 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, causing congestive heart failure.