Renal or kidney failure is the condition in which the kidneys do not produce enough urine to get rid of the body's waste products. Healthy adults need to produce at least 400 ml of urine a day. When the kidneys suddenly produce less than this amount, acute renal failure (ARF) occurs. Acute renal failure can be caused by trauma, infection, toxic substances or kidney stones.
Pre-Renal ARF
Pre-renal ARF occurs from a severe or prolonged decrease in blood flow to the kidneys, according to the 2006 edition of "Medical-Surgical Nursing-Critical Thinking for Collaborative Care" textbook. Severe dehydration, loss of blood or septic shock can lead to low blood pressure, which decreases the amount of blood flowing through the kidneys. Damage to the part of the kidney that filters waste products from the blood results, causing acute renal failure.
Intra-Renal ARF
Medications and chemicals can be toxic to the kidneys. Infections and autoimmune disorders such as lupus or sickle-cell disease may damage kidney tissue directly causing acute renal failure.
Post-Renal ARF
Post-renal ARF occurs when there is a blockage of urine output from the kidney. Kidney stones, blood clots, strictures, swelling of the urethra or tumors may prevent the excretion of urine.
Oliguria
Acute renal failure has three stages, the first of which is called oliguria. Urine output is less than 400 ml per day, causing azotemia, the buildup of nitrogenous waste products in the blood. Symptoms characteristic of ARF oliguria include nausea, vomiting, headache, dizziness, dry itchy skin, malodorous breath, fluid retention with swelling and an elevated heart rate and blood pressure. As azotemia worsens, drowsiness, confusion, abnormal heart rhythms, coma and death may occur.
Renal replacement therapy, or dialysis, may be needed to sustain the patient until the condition causing the acute renal failure is corrected. Rinaldo Bellomo, M.D., lead author for the Acute Dialysis Quality Initiative report published in the May 2004 issue of "Critical Care," explained that dialysis should be needed for only about four weeks. Anything longer indicates chronic renal failure or end stage renal disease.
According to Scott and White Hospital, characteristic lab work changes occur within a few days to two weeks of acute renal failure. Blood urea nitrogen (BUN), a byproduct of protein synthesis, or breakdown, will be elevated, indicating decreased kidney function. A creatinine clearance test, which indicates how well the kidneys are filtering wastes from the blood, will be lower than normal. The kidneys will not excrete as much potassium as normal, causing high potassium blood levels.
Diuresis
During this stage of acute renal failure, filtering ability is poor and the kidneys cannot concentrate urine. Four to 10 liters of dilute urine may be produced daily. Patients are at risk for dehydration and electrolyte imbalances. Sodium and potassium will be low, causing irregular heart rhythms, weakness and fatigue.
Recovery
Recovery of acute renal failure is gradual. Only when the kidneys can concentrate urine and produce adequate output, and lab values have returned to normal levels, is recovery achieved.
References
- "Critical Care: Acute renal failure -- definition, outcome measures, animal models, fluid therapy and information technology needs"; Rinaldo Bellomo, et al; 2004
- "Medical-Surgical Nursing-Critical Thinking for Collaborative Care"; Donna D. Ignatavicius, M.S., R.N. and M. Linda Workman, Ph.D.; 2006
- Scott and White Hospital: Acute Renal Failure
