Acute Renal Failure
Acute renal failure is characterized by the fact that the kidneys suddenly no longer fulfill their normal function. Normally kidneys filter the toxic byproducts (waste) and maintain normal levels of water, salt and minerals (electrolytes) in the blood. When kidneys stop working properly, products of metabolism, fluids and electrolytes accumulate in the body, situation which can be life threatening.
A number of diseases and special conditions can cause the kidneys to stop working normally. A patient may develop acute renal failure if:
- Lost a large amount of blood. This can occur due to a serious injury or major surgery. Was dehydrated due to excessive vomiting or excessive use of diuretics.
- Has a serious heart disease such as heart failure, myocardial infarction, arrhythmia (abnormal heart rhythm), hypertension, endocarditis, valvular or cardiac tamponade.
- Has a condition that may affect the kidneys or liver, such as nephrotic syndrome, cirrhosis, lupus or another disease that causes inflammation of blood vessels (vasculitis)
- Has other serious illness, as severe malnutrition, burns, serious harm or stress syndrome or severe infection (sepsis)
- Uses drugs that may affect the kidneys, including antibiotics such as gentamicin or streptomycin, converting enzyme inhibitors for high blood pressure values, NSAIDs, like aspirin or ibuprofen or contrast agents used in some X-ray investigations.
- Develops a sudden obstruction at some level in the urinary tract that blocks the elimination of urine from the kidney due to kidney stones, kidney tumors, injurys to the urinary tract or an enlarged prostate that can cause blockages.
Acute renal failure often causes no symptoms that the patient can notice. If the patient is in hospital, investigations performed for other conditions can detect the kidney damage. Symptoms that can occur:
- Swelling of legs and feet (edema)
- Small-production of urine or lack of it (oligoanury)
- Thirst and dry mouth
- Tachycardia (accelerated heart rate)
- Feeling of dizziness when the patient stands
- Loss of appetite, nausea and vomiting
- Confusion, anxiety, restlessness or drowsiness.
- Pain on either side, just below the rib cage up to the waist (flank pain).
Symptoms can help determine the type of kidney failure. Severe dehydration, a common cause of acute renal failure may cause thirst, lack of dexterity (coordination) or light-headedness and a rapid and weak pulse . Obstruction of the urinary tract, causing acute postrenal kidney failure can cause flank pain or renal lodges pain, blood in the urine (hematuria) or reduced urinary output (oliguria). Uremic syndrome (uremia) is a serious complication of prolonged and severe acute renal failure. It can cause severe drowsiness, confusion, convulsions, irregular heart rhythm and fluid accumulation in the lungs (pulmonary edema)
Acute renal failure develops within a few hours to several days when the kidneys lose their ability to remove products of metabolism and excess body fluids. The most common cause is reduced blood flow to the kidneys due to dehydration, surgery, an infection or a severe injury. When blood flow to the kidneys decreases, toxic byproducts and excess fluid are not removed properly from the body. Acute renal failure can cured with treatment within days or week but some people produce permanent alterations in kidney structure leading to chronic renal failure. A small percentage of them will rely on regular dialysis or will need a kidney transplant. Left untreated acute renal failure may develop complications that affect the entire body. These include:
- Infection. It is one of the most frequent complications due to the patient’s immune system which does not work properly
- Uremic syndrome (uremia). May cause dizziness, confusion, convulsions, irregular heart rhythm and accumulation of fluid in the lungs (pulmonary edema)
- Raise in blood potassium levels (hyperkalemia). This can lead to serious heart problems.
Almost half of those who developed acute renal failure recover sufficiently their renal function to lead a normal life.
Older people and those with serious medical problems are less likely to regain their previous health. Those who die, do so due to the condition that caused kidney failure and renal failure not due to renal failure itself.
People with certain illnesses or diseases and elderly persons are more prone to acute renal failure. Diseases that may increase the risk for renal failure are:
- Kidney disease such as nephrotic syndrome or liver disease such as liver cirrhosis
- Heart failure
Acute renal failure usually occurs in people who are already seriously ill or already in the hospital or in intensive care. People who have had heart surgery or abdominal or bone marrow transplant have a higher risk.
Diagnosis and investigations
The doctor will start evaluating patients with acute renal failure by making a case history and a physical exam. This includes a review of medical history and history of hospitalization (if the patient is hospitalized at the time), a record of drugs that the patient has used, an assessment of other conditions that could cause the appearance of acute renal failure. When acute renal failure is suspected, a complete evaluation is needed to determine the cause of kidney failure. This is an important part of diagnosis. The decision of treatment and chances of recovery depend usually on the causes of kidney failure. Identifying the cause is sometimes difficult and requires more investigations
Blood and urine tests are performed routinely to evaluate acute renal failure. They can detect high levels of metabolic products in blood and a chemical imbalance in the body and can help diagnose and detect diseases or infections. Blood and urine tests may include:
- Serum creatinine. An increase in blood creatinine (serum creatinine) is usually the first sign of acute renal failure. Repeated testing of the creatinine level can help monitor progression of renal failure and determining the effective treatment. In the case of prerenal acute kidney failure for example, serum creatinine levels will rapidly return to normal once blood flow or volume depletion (fluid loss) are restored.
- Creatinine clearance. Estimates the remaining functional kidney by comparing the blood levels of creatinine with the levels of urine creatinine. When kidneys stop functioning properly, blood creatinine levels may increase while urinary creatinine levels may decrease
- Serum urea is the nitrogen amount found in the urea, an indicator of nitrogen retention (azotemia). When acute renal failure is present, serum urea level increases. Blood electrolytes that are tested are calcium, potassium and sodium.
- Blood count (CBC). CBC provides important information about red blood cells, white cells and platelets. Can be used to search for diseases or infections that could be the cause of kidney failure
- Other blood tests as erythrocyte sedimentation rate (ESR) and antinuclear antibodies (ANA) can be used to diagnose an infection, an autoimmune disease or other diseases if the patient history and symptoms suggest that one of these diseases could be present.
Urine tests performed:
- Urine analysis results can also provide information about urinary sediment, which is useful to assess acute renal failure (of renal cause)
- Urinary eosinophils (a type of white blood cells). The existence of eosinophils in the urine may indicate an allergic reaction that destroys the kidney. Often the allergic reaction is caused by a certain drug.
- The fraction of sodium excreted in urine. This examination can help differentiate between prerenal renal failure, where there is no damage to the kidney. Measures the kidney ability to eliminate sodium (Na), based on sodium and creatinine levels in both urine and blood
- 24-hour collected urine. Urine production is measured over a period of 24 hours. Sometimes it requires a probe to collect all urine produced correctly. Reduced urine production may or may not be present along with kidney failure, depending on the cause. Careful measurement of urine output over time, can also help monitor fluid balance in a person with kidney failure.
Imaging tests may be used to determine whether to determine the nature of renal failure: acute or chronic. Also an obstruction in the urinary tract can be revealed. Imaging tests most commonly used for this purpose are:
- Abdominal ultrasound
- Abdominal radiography or urography, which can be used when a kidney stone is suspected . If there is belief that the obstruction is the cause of postrenal kidney failure, more detailed tests may be needed to determine the location and cause of obstruction.
These examinations can include those above and also:
- Retrograde pyelography
- Renal scintigraphy (may help assess renal blood flow, if normal, or to determine if an obstruction is present).