Acute renal failureProblem: A man comes to a clinic complaining of asthenia, malaise, headache, weight gain, and decreased urination. A provisional diagnosis of acute renal failure is made. The general term for a sudden and prolonged decrease in kidney function is called acute renal failure. This is the retention of urea, creatinine and waste products. Prerenal, intrarenal, and postrenal are subclassifications for acute renal failure. Prerenal is the most common form of renal failure. Reduced/interrupted blood flow to the kidney can cause tissue damage and restore the kidney's ability to function. This includes burns, loss of blood volume, heart failure, shock, long-term vomiting/diarrhea/bleeding, kidney injury, and some types of surgery. Prerenal failure, if identified early and treated correctly, can be reversible. Intrarenal failure is the actual damage to the nephrons and renal parenchyma. This can be classified as acute tubular necrosis and is a common type of acute renal failure in critically ill patients. This is a type of kidney failure that is reversible, but it can take weeks or months for kidney function to return adequately. The condition that causes urinary flow obstruction is postrenal insufficiency. Any condition such as tumors, benign prostatic hypertrophy, kidney stones, and bladder neck obstruction can cause this type of acute kidney failure. If left untreated, the result is actual nephron damage and intrarenal failure. A patient with kidney disease will undergo laboratory testing, but a full and complete medical history will be taken first. Physically the patient's body will show swelling caused by fluid retention and murmur in the heart, crackles in the lungs or abnormal sounds may be found in the heart or lungs. These tests include blood urea nitrogen (normal range 6-20 mg/dL), creatinine clearance (compares creatinine levels in urine and blood), serum creatinine, serum potassium, and urinalysis. The preferred test to diagnose a urinary tract blockage would be an ultrasound. X-rays or MRI can also tell if there is a blockage, and the blood test will help reveal the underlying cause of kidney failure. Insufficient filtering of the blood by the kidney causing high levels of nitrogen-containing compounds and other waste products is called azotemia. . This waste product is normally excreted in the urine and can lead to uremia. In Uremia the waste products are now present in the blood. With oliguria the body receives an abnormally small amount of urine.