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Renal Failure, Acute

Also known as:   Acute Tubular Necrosis

Obstruction, reduced circulation, and renal parenchymal disease can all cause the sudden interruption of kidney function. Acute renal failure is usually reversible with medical treatment; otherwise, it may progress to end-stage renal disease, uremic syndrome, and death.

Causes

Acute renal failure can be classified as prerenal, intrinsic (or parenchymal), and postrenal.

Prerenal failure

Diminished blood flow to the kidneys causes prerenal failure. Such decreased flow may result from hypovolemia, shock, embolism, blood loss, sepsis, pooling of fluid in ascites or burns, and cardiovascular disorders, such as heart failure, arrhythmias, and tamponade.

Intrinsic renal failure

Parenchymal, or intrinsic, renal failure results from damage to the kidneys themselves, usually resulting from acute tubular necrosis. Such damage may also result from acute poststreptococcal glomerulonephritis, systemic lupus erythematosus, polyarteritis nodosa, vasculitis, sickle-cell disease, bilateral renal vein thrombosis, nephrotoxins, ischemia, renal myeloma, and acute pyelonephritis.

Postrenal failure

Bilateral obstruction of urinary outflow results in postrenal failure. Its multiple causes include kidney stones, clots, papillae from papillary necrosis, tumors,benign prostatic hyperplasia, strictures, and urethral edema from catheterization.

Signs and symptoms

Acute renal failure is a critical illness. Its early signs are oliguria, azotemia and, rarely, anuria. Electrolyte imbalances, metabolic acidosis, and other severe effects follow as the patient becomes increasingly uremic and renal dysfunction disrupts other body systems:

• GI-anorexia, nausea, vomiting, diarrhea or constipation, stomatitis, bleeding, hematemesis, dry mucous membranes, uremic breath
• central nervous system (CNS)­headache, drowsiness, irritability, confusion, peripheral neuropathy, seizures, coma
• cutaneous-dryness, pruritus, pallor, purpura; rarely, uremic frost
• cardiovascular-early in the disease, hypotension; later, hypertension, arrhythmias, fluid overload, heart failure, systemic edema, anemia, altered clotting mechanisms
• respiratory- Kussmaul's respirations, pulmonary edema.

Fever and chills indicate infection, a common complication.

Diagnosis

To diagnose acute renal failure, your doctor will review your medical history and symptoms to determine the cause of your condition. He or she will perform a thorough physical examination, checking specifically for any enlargement or tenderness in the kidney area. You may be referred to a nephrologist, who specializes in kidney function. Your doctor will order blood and urine tests to check levels of waste products, sodium, and potassium in your bloodstream and urine. Levels of a waste product called creatinine and urea will be high in patients with renal failure. Your physician will check your bladder and may need to insert a tube, called a catheter, into the bladder to remove urine. Your doctor will also order ultrasound, computed tomography (CT), or magnetic resonance imaging (MRI) scans, which produce a picture of the kidneys and surrounding structures. In some cases, a biopsy is necessary. In this procedure, a small sample of kidney tissue is removed for examination under a microscope.

Treatment

Supportive measures include a diet high in calories and low in protein, sodium, and potassium, with supplemental vitamins and restricted fluids. Meticulous electrolyte monitoring is essential to detect hyperkalemia.

If hyperkalemia occurs, acute therapy may include dialysis, hypertonic glucose and insulin infusions, and sodium bicarbonate - all administered I.V ­and sodium polystyrene sulfonate, given orally or by enema, to remove potassium from the body.

If measures fail to control uremic symptoms, hemodialysis or peritoneal dialysis may be necessary.

Prevention

Since acute kidney failure can be caused by many things, prevention is difficult. Medications that may impair kidney function should be given cautiously. Patients with pre-existing kidney conditions who are hospitalized for other illnesses or injuries should be carefully monitored for kidney failure complications. Treatments and procedures that may put them at risk for kidney failure (like diagnostic tests requiring radiocontrast agents or dyes) should be used with extreme caution.