Chronic Renal Failure

Chronic renal failure is usually the end result of a grad­ually progressive loss of renal function. It also occasionally results from a rapidly progressive disease of sudden onset that gradually destroys the nephrons and eventually causes irreversible renal damage. 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.

Chronic renal failure may progress through the following stages:

• reduced renal reserve (glomerular filtration rate [GFR] 5% to 50% of normal)
• renal insufficiency (GFR 20% to 35% of normal)
• renal failure (GFR 20% to 25% of normal)
• end-stage renal disease (GFR less than 20% of normal).

This syndrome is fatal without treatment, but maintenance dialysis or a kidney transplant can sustair life.

Causes

The two most commons causes of kidney failure are:

• Diabetes – longstanding high blood sugar that results from diabetes damages the nephrons
• High blood pressure – longstanding high blood pressure damages the capillaries in the kidneys

Others causes of kidney failure may include:

• Pyelonephritis
• Glomerulonephritis
• Polycystic kidney disease
• Birth defects
• Poisoning
• Severe trauma

Signs and Symptoms

Initial symptoms may include the following:

• Unintentional weight loss
• Nausea, vomiting
• General ill feeling
• Fatigue
• Headache
• Frequent hiccups
• Generalized itching (pruritus)

Later symptoms may include the following:

• Increased or decreased urine output
• Need to urinate at night
• Easy bruising or bleeding
• May have blood in the vomit or in stools
• Muscle twitching or cramps
• Seizures
• Uremic frost deposits of white crystals in and on the skin
• Decreased sensation in the hands, feet, or other areas

Diagnostic tests

Various laboratory findings aid in the diagnosis and monitoring of chronic renal failure. For example, blood studies show elevated blood urea nitrogen, serum creatinine, sodium, and potassium levels; decreased arterial pH and bicarbonate levels; low hematocrit and hemoglobin levels; decreased red blood cell (RBC) survival time; mild thrombocytopenia; platelet defects; and metabolic acidosis. They also show increased aldosterone secretion (related to increased renin production) and increased blood glucose levels similar to those that occur in diabetes mellitus (a sign of impaired carbohydrate metabolism). Hypertriglyceridemia and decreased high-density lipoprotein levels are common.

Arterial blood gas analysis reveals metabolic acidosis.

Urine specific gravity becomes fixed at 1.010; urinalysis may show proteinuria, glycosuria, RBCs, leukocytes, and casts and crystals, depending on the cause.

X-ray studies, including kidney-ureter-bladder radiography, excretory urography, nephrotomography, renal scan, and renal arteriography show reduced kidney size.

Renal biopsy allows histologic identification of the underlying pathology.

EEG shows changes that indicate metabolic encephalopathy.

Treatment

The goal of conservative treatment is to correct specific symptoms. 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 have a high-protein diet.) A high-calorie diet prevents ketoacidosis and the negative nitrogen balance that results in catabolism and tissue atrophy. The diet should restrict sodium, phosphorus, and potassium.

Maintaining fluid balance requires careful monitoring of vital signs, weight changes, and urine volume (if not anuric). Fluid retention can be reduced with loop diuretics such as furosemide (if some renal function remains) and with fluid restriction. Digitalis glycosides in small doses may be used to mobilize the fluids causing the edema; antihypertensives may be used to control blood pressure and associated edema.

Antiemetics taken before meals may relieve nausea and vomiting, and cimetidine or ranitidine may decrease gastric irritation. Methylcellulose or docusate can help prevent constipation.

Anemia necessitates iron and folate supplements; severe anemia requires infusion of fresh frozen packed cells or washed packed cells. Transfusions relieve anemia only temporarily. Synthetic erythropoietin (epoetin alfa) stimulates the division and differentiation of cells within the bone marrow to produce RBCs.

Drug therapy commonly relieves associated symptoms. An antipruritic, such as trimeprazine or diphenhydramine, can relieve itching, and aluminum hydroxide gel can lower serum phosphate levels. The patient also may benefit from supplementary vitamins (particularly vitamins B and D) and essential amino acids.

Alert Careful monitoring of serum potassium levels is necessary to detect hyperkalemia. Emergency treatment for severe hyperkalemia includes dialysis therapy and administration of 50% hypertonic glucose I.V., regular insulin, calcium gluconate I.V., sodum bicarbonate I.V., and cation exchange resins such as sodium polystyrene sulfonate. Cardiac tamponade resulting from pericardial effusion may require emergency pericardial tap or surgery.

Calcium and phosphorus imbalances may be treated with phosphate binding agents, calcium supplements, and reduction of phosphorus in the diet. If hyperparathyroidism develops secondary to low serum calcium levels, a parathyroidectomy may be performed

Intensive dialysis and thoracentesis can relieve pulmonary edema and pleural effusion.

Hemodialysis or peritoneal dialysis (particularly the newer techniques, such as continuous ambulatory peritoneal dialysis and continuous cyclic peritoneal dialysis) can help control most manifestations of end-stage renal disease. Altering the dialysate can correct fluid and electrolyte disturbances. However, maintenance dialysis itself may produce complications, including serum hepatitis (hepatitis B) from numerous blood transfusions, protein wasting, refractory ascites. and dialysis dementia.

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.