Acute renal failure (ARF) is the rapid loss of kidney function occurring when high levels of uremic toxins accumulate in the blood. ARF occurs when the kidneys are unable to excrete the daily load of toxins in the urine. The most common causes of ARF are dehydration, blood loss from major surgery or injury, or medications such as NSAIDs, antibiotics, or the dyes used in X-ray tests (see table 1 below). ARF causes can be distributed into three categories, including prerenal, postrenal, and intrinsic (Mayo clinic, 2008).
To start with, prerenal failure is the most common ARF and accounts for 60-70% of all cases (Cunha, 2000). Prerenal failure is characterized by inadequate blood circulation to the kidneys, which leaves them unable to clean the blood properly. Many patients with prerenal failure are critically ill and often experience shock. There is often poor perfusion within many organs, which may lead to multiple organ failure. Prerenal failure is associated with a number of preexisting medical conditions, such as atherosclerosis, which reduces blood flow. Dehydration is one of the main causes, due to reduced fluid intake or excessive use of diuretics. During prerenal failure damage is minimal and can be reversed with proper treatment. Permanent damage can occur with prolonged decrease in blood flow to the kidneys (Rhodes, 2009).
Next, postrenal failure accounts for 5-10% of all cases, therefore being the least common cause (Cunha, 2000). Postrenal failure is caused by an acute obstruction that affects the normal flow of urine out of both kidneys. The blockage causes fluid pressure to build in all of the renal nephrons, causing them to shut down. The degree of renal failure corresponds directly with the degree of obstruction. Postrenal failure is seen most often in urethral, bladder, or ureteral obstructions. Kidney stones, a tumor, an injury, or an enlarged prostate gland can cause a blockage. The kidneys usually recover after removing the blockage with certain treatments.
Finally, ARF that is not caused by prerenal or postrenal factors is categorized as intrinsic acute renal failure. This type of failure involves damage or injury within both kidneys, due to reduced blood flow. Approximately 40% of ARF cases are intrinsic failure (Cunha, 2000). Most intrinsic renal failure cases are caused by ischemia or toxins, both of which lead to acute tubular necrosis (ATN); a condition where the filtering tubes in the kidneys are damaged. ATN often occurs because of decreased blood flow due to surgery, severe burns, or muscle injury. Certain medications can be toxic to the kidneys if a person has a medical history of kidney problems, heart failure, or diabetes. Intrinsic renal failure leads to tissue death and cannot be reversed (Rhodes, 2009).
Contributing factors and prognosis
ARF almost always occurs in connection with another medical condition; hypertension and diabetes are two of those conditions. When a person has high blood pressure it causes the heart to work harder, in turn causing damage to blood vessels. In the United States alone there are over 25,000 new cases of ARF related to high blood pressure every year (NIDDK, 2008). Diabetes is another main cause of kidney failure; this is due to too much blood glucose in the body causing damage to the kidneys’ filters. When the blood vessels or filters are damaged in the kidneys they are not able to excrete waste and fluid (NIDDK, 2008). Other contributing factors might include dehydration, hypotension - due to surgery, heart failure, hemorrhage, liver disease, or...