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Renal Failure, Chronic

Although chronic renal failure is usually the result of a gradually progressive loss of renal function, it occasionally results from a rapidly progressive disease of sudden onset. Few symptoms develop until after more than 75% of glomerular filtration is lost; then, the remaining normal parenchyma deteriorates progressively, and symptoms worsen as renal function decreases.

If this condition continues unchecked, uremic toxins accumulate and produce potentially fatal physiologic changes in all major organ systems. If the patient can tolerate it, maintenance dialysis or kidney transplantation can sustain life.

Causes

Chronic renal failure may result from:

• chronic glomerular disease such as glomerulonephritis
• chronic infections, such as chronic pyelonephritis or tuberculosis
• congenital anomalies such as polycystic kidneys
• vascular diseases, such as renal nephrosclerosis or hypertension
• obstructive processes such as calculi
• collagen diseases such as systemic lupus erythematosus
• nephrotoxic agents such as long-term aminoglycoside therapy
• endocrine diseases such as diabetic neuropathy.

Such conditions gradually destroy the nephrons and eventually cause irreversible renal failure. Similarly, acute renal failure that fails to respond to treatment becomes chronic renal failure.

Chronic renal failure may progress through the following stages:

• reduced renal reserve (glomerular filtration rate [GFR] 40 to 70 ml/minute)
• renal insufficiency (GFR 20 to 40 ml/minute)
• renal failure (GFR 10 to 20 mil minute)
• end-stage renal disease (GFR < 10 ml/minute ).

Signs and symptoms

Chronic renal failure produces major changes in all body systems

Renal and urologic changes

Initially, salt-wasting and consequent hyponatremia produce hypotension, dry mouth, loss of skin turgor, listlessness, fatigue, and nausea. Later, somnolence and confusion develop.

As the number of functioning nephrons decreases, so does the kidneys' capacity to excrete sodium, resulting in salt retention and overload. Accumulation of potassium causes muscle irritability, then muscle weakness as the potassium level continues to rise.

Fluid overload and metabolic acidosis also occur. Urine output decreases; urine is very dilute and contains casts and crystals.

Cardiovascular changes

Renal failure leads to hypertension and arrhythmias, including life-threatening ventricular tachycardia or fibrillation. Other effects include cardiomyopathy, uremic pericarditis, pericardial effusion with possible cardiac tamponade, heart failure, and peripheral edema.

Respiratory changes

Pulmonary changes include reduced pulmonary macrophage activity with increased susceptibility to infection, pulmonary edema, pleuritic pain, pleural friction rub and effusions, and uremic pleuritis and uremic lung (or uremic pneumonitis). Dyspnea from heart failure also occurs, as do Kussmaul's respirations as a result of acidosis.

GI changes

Inflammation and ulceration of GI mucosa cause stomatitis, gum ulceration and bleeding and, possibly, parotitis, esophagitis, gastritis, duodenal ulcers, lesions on the small and large bowel, uremic colitis, pancreatitis, and proctitis. Other GI symptoms include a metallic taste in the mouth, uremic fetor (ammonia smell to breath), anorexia, nausea, and vomiting.

Cutaneous changes

Typically, the skin is pallid, yellowish bronze, dry, and scaly. Other cutaneous symptoms include severe itching; purpura; ecchymoses; petechiae; uremic frost (most often in critically ill or terminal patients); thin, brittle fingernails with characteristic lines; and dry, brittle hair that may change color and fall out easily.

Neurologic changes

Restless leg syndrome, one of the first signs of peripheral neuropathy, causes pain, burning, and itching in the legs and feet, which may be relieved by voluntarily shaking, moving, or rocking them. Eventually, this condition progresses to paresthesia and motor nerve dysfunction (usually bilateral footdrop) unless dialysis is initiated.

Other signs and symptoms include muscle cramping and twitching, shortened memory and attention span, apathy, drowsiness, irritability, confusion, coma, and seizures. Electroencephalogram changes indicate metabolic encephalopathy.

Endocrine changes

Common endocrine abnormalities include stunted growth patterns in children (even with elevated growth hormone levels), infertility and decreased libido in both sexes, amenorrhea and cessation of menses in women, and impotence and decreased sperm production in men. Other changes include increased aldosterone secretion (related to increased renin production) and impuired carbohydrate metabolism (causing increased blood glucose levels similar to those found in diabetes

Hematopoietic changes

Anemia, decreased red blood cell (RBC) survival time, blood loss from dialysis and GI bleeding, mild thrombocytopenia, and platelet defects occur. Other problems include increased bleeding and clotting disorders, demonstrated by purpura, hemorrhage from body orifices, easy bruising, ecchymoses, and petechiae.

Skeletal changes

Calcium-phosphorus imbalance and consequent parathyroid hormone imbalances cause muscle and bone pain, skeletal demineralization, pathologic fractures, and calcifications in the brain, eyes, gums, joints, myocardium, and blood vessels. Arterial calcification may produce coronary artery disease. In children, renal osteodystrophy (renal rickets) may develop.

Diagnosis

Clinical assessment, a history of chronic progressive debilitation, and gradual deterioration of renal function as determined by creatinine clearance tests lead to a diagnosis of chronic renal failure.

The following laboratory findings also aid in diagnosis:

• Blood studies show elevated blood urea nitrogen, serum creatinine, and potassium levels; decreased arterial pH and bicarbonate; and low hemoglobin (Hb) and hematocrit (HCT).
• Urine specific gravity becomes fixed at 1.010; urinalysis may show proteinuria, glycosuria, erythrocytes, leukocytes, and casts, depending on the etiology.
• X-ray studies include kidney-ureterbladder radiography, excretory urography, nephrotomography, renal scan, and
• Kidney biopsy allows histologic identification of underling pathology.

Treatment

Treatment for chronic renal failure depends upon the cause. While treating any underlying disease may relieve some of the strain on the kidneys, your doctor will also recommend changes in your diet that will help prevent your condition from becoming progressively worse. For example, you may need to decrease your intake of sodium, potassium, proteins, and fluids. You may need to take medications to treat high blood pressure, anemia, or high cholesterol. All patients in kidney failure are monitored for intake and output of fluids so treatment and medications can be adjusted as necessary. In severe cases, patients will need dialysis, a procedure in which waste products are filtered from the blood for the kidneys, or a kidney transplant.

Diet

A low-protein diet reduces the production of end-products of protein metabolism that the kidneys can't excrete. (A patient receiving continuous peritoneal dialysis should receive a high-protein diet.)

A high-calorie diet prevents ketoacidosis and the negative nitrogen balance that results in catabolism and tissue atrophy. Such a diet also restricts sodium and potassium.

Prevention

Treatment of the underlying disorders may help prevent or delay development of chronic renal failure. Diabetics should control blood sugar and blood pressure closely and should refrain from smoking.