Renal failure describes a condition in which the kidneys have lost the ability to perform their primary function of eliminating excess fluid and waste from the body. Kidney failure can develop suddenly (acute renal failure) or slowly over a number of years (chronic renal failure). Kidney failure is further categorized by the location of the problem: prerenal, intrinsic or postrenal.
Acute Prerenal Kidney Failure
Acute prerenal kidney failure is a sudden loss of kidney function due to inadequate delivery of blood to the kidneys. There is nothing wrong with the kidneys' filtering capacity. Rather, the problem in this circumstance is one of supply---the kidneys cannot filter what they do not receive. Prerenal conditions are the most frequently encountered cause of acute renal failure. Common precipitating conditions include: low blood pressure due to severe blood loss or dehydration, overwhelming infection and heart failure. This type of renal failure is usually quickly reversible if the underlying condition is controlled such that adequate blood flow to the kidneys is restored.
Acute Intrinsic Kidney Failure
Acute intrinsic kidney failure is a sudden loss of function caused by direct kidney damage. Ninety percent of cases of this form of acute renal failure are caused by toxins or insufficient oxygen to the kidneys (ischemia). Causative toxins include certain antibiotics, chemotherapy drugs, medical imaging contrast dyes and some organic solvents. Ischemia can be caused by systemic conditions such as severe bleeding or shock, or local blood supply problems such as obstruction of the renal blood vessels or glomerulonephritis.
Chronic Prerenal Kidney Failure
When delivery of blood to the kidneys remains low for a long period, they begin to shrink and slowly stop functioning, which is a classic example of "use it or lose it." Chronic liver failure, atherosclerosis of the renal blood vessels and long-standing heart failure can cause chronic prerenal kidney failure.
Chronic Intrinsic Kidney Failure
Approximately 80 percent of chronic renal failure is caused by intrinsic kidney disease, that is long-term damage to the kidneys themselves. Kidney disease caused by long-standing diabetes (called diabetic nephropathy) is the leading cause of chronic kidney disease, accounting for roughly 44 percent of cases. Chronic hypertension follows accounting for nearly 27 percent.
Chronic Postrenal Kidney Failure
Prolonged partial obstruction of urinary outflow causes a pressure backup in the kidneys, which damages them. Prostate enlargement, kidney stones, bladder stones and neurogenic bladder can cause this type of renal failure.
References
- "Harrison's Principles of Internal Medicine, 14th Edition"; Multiple Authors, Editors; 1998
- Merck Manual: Acute Renal Failure
- Merck Manual: Chronic Kidney Disease
- Mayo Clinic: Causes, Acute Renal Failure
- Mayo Clinic: Causes, Chronic Renal Failure
