Acute renal failure means the kidneys are quickly losing their ability to function. It can happen in a matter of weeks or in just a few days. Acute renal failure has three categories: renal, postrenal and prerenal. The renal category includes injuries within the kidney itself. Postrenal includes causes for why the flow of urine is blocked. In prerenal failure, the kidneys are not getting enough blood.
Hypovolemia
According to Elizabeth Corwin, Ph.D., in "Handbook of Pathophysiology," the heart pumps five liters of blood every minute. And every minute, one liter of blood goes to the kidneys. The kidneys need this amount of blood to function properly. But the kidneys will not get enough blood, not receive one liter every minute, if a person has a low amount. Hypovolemia is the word used to describe a low volume of blood. Someone can become hypovolemic if she is severely dehydrated, is hemorrhaging, has lost a lot of fluids because of burns or if she has excessive vomiting, diarrhea or urination.
Septic Shock
In severe septic shock, a person has a bacterial infection, the failure of at least one organ and low blood pressure. Dr. Max Weil explains the process in "The Merck Manual for Healthcare Professionals." He states that at first, the heart pumps out more blood, which is called "warm shock," and the skin will be warm. But then, the heart pumps less and a person's blood pressure drops. Now the person is in "cold shock," with cool skin. A low blood pressure means less blood is going to the kidneys.
Cardiac Tamponade
The pericardium is a membrane that covers the heart. This membrane has two layers. Dr. Martin LeWinter, a cardiologist and director at Fletcher Allen Health Care, writes in "Current Diagnosis & Treatment: Cardiology," that cardiac tamponade is when fluid builds up in the pericardium, presses down on the heart and stops the heart from being able to pump out the normal amount of blood. This means the kidneys will not get the amount of blood they need to function.
Renal Artery Stenosis
The word stenosis describes when a blood vessel or heart valve narrows. Dr. Seyed-Ali Sadjadi, associate professor of medicine at Loma Linda University School of Medicine, writes in "The Merck Manual for Healthcare Professionals" that renal artery stenosis is when the renal artery of one or both kidneys has become narrow. Thus, less blood reaches that kidney (or kidneys).
Renal Artery Occlusion
In renal artery occlusion, according to Dr. Sadjadi, something is occluding or blocking the flow of blood through the artery. A blood clot or atherosclerosis, for example, can occlude blood flow. And just like in a stenosis, an occlusion can decrease the blood flow to the kidneys so much that it can lead to prerenal failure.
References
- "Current Diagnosis & Treatment: Cardiology"; Michael Crawford, M.D.; 2009
- "Handbook of Pathophysiology"; Elizabeth Corwin, MSN, Ph.D., FNP; 2000
- The Merck Manual: Renal Artery Stenosis and Occlusion
- The Merck Manual: Sepsis and Septic Shock
