Kidney Failure in Infants and Children

James C. M. Chan; Debra M. Williams; Karl S. Roth

doi:10.1542/pir.23-2-47

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James C. M. Chan, MD*†
Debra M. Williams, MD*
Karl S. Roth, MD*†

^*Department of Pediatrics, Virginia Commonwealth University, Medical College of Virginia Campus, Richmond, VA
^†Department of Biochemistry, Virginia Commonwealth University, Medical College of Virginia Campus, Richmond, VA

Objectives

After completing this article, readers should be able to:

Recognize and delineate the causes of acute renal failure.
Formulate emergency management of fluid electrolyte disorders in acute renal failure.
Characterize the incidence, causes, and costs of chronic renal failure in children.
Explain the pathogenesis and treatment of complications of chronic renal failure.
Delineate a plan to help the family with the outcome of renal failure.

Introduction

The evaluation of kidney failure is challenging, despite many advances in diagnosis and treatment over the past decade. To provide pediatricians with an informed choice, this article reviews both acute and chronic renal failure, their multiple causes, the principles of treatment, and both short- and long-term outcomes.

Acute renal failure (ARF) is characterized by the abrupt failure of the kidneys to regulate water and electrolyte homeostasis. ARFs in childhood due to hemolytic-uremic syndrome, postinfectious acute glomerulonephritis, or dehydration are reversible, but a small percentage may progress to chronic renal failure (CRF). CRF is the result of slowly progressive kidney diseases and seldom is fully reversible. This condition in childhood is associated with obstructive uropathy, congenital aplastic/hypoplastic/dysplastic kidneys, and other causes. In CRF, almost every system in the body eventually becomes compromised.

Acute Renal Failure

Incidence and Causes

ARF is encountered in 3% to 10% of all admissions to neonatal intensive care units. In our experience with a regional pediatric nephrology program serving a catchment area of 1.5 million general population, 6.4% of 3,154 children referred to the program from community physicians suffered from ARF. However, precise figures on the true incidence of ARF in childhood are surprisingly sparse.

ARF is a life-threatening, abrupt reduction of urinary output to less than 300 mL/m² per day that is precipitated by prolonged renal ischemia in most cases. Occasionally, it may present with a high urinary output but mounting serum urea nitrogen and creatinine levels, the so-called “high output” or “nonoliguric” ARF, more often following severe burns or open heart surgery. The three leading causes of acute renal failure in children (Table 1) in developing countries are: hemolytic-uremic syndrome (31%), glomerulonephritis (23%), and postoperative sepsis/prerenal ischemia (18%). In contrast, for industrialized countries, the three most common causes are: intrinsic renal disease (44%), postoperative septic shock (especially after open heart surgery) (34%), and organ/bone marrow transplantation (13%).

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TABLE 1.

Causes of Acute Renal Failure in Children

Proximal tubular necrosis may follow toxic ingestions (eg, carbon tetrachloride, diethylene glycol, arsenic, mercury, gold, lead, and other heavy metals). Medications, such as sulfonamide, kanamycin, and neomycin, and radiocontrast material occasionally are reported to precipitate tubular patchy necrosis. Newer medications that may precipitate acute tubular necrosis include intravenous immunoglobulin, acyclovir, ibuprofen, angiotensin-converting enzyme inhibitors, cyclosporin, and tacrolimus.

Tubular and vascular obstruction causing prolonged renal ischemia may follow renal parenchymal uric acid accumulation, sickle cell crisis, myoglobulinemia, and renal vein thrombosis.

Cortical and tubular necrosis may occur following hemorrhagic shock, severe dehydration, crush injuries, thermal burns, and septic shock.

In neonates, asphyxia, erythroblastosis, cardiac pump oxygenation, or mechanical ventilation all may compromise renal function and predispose the infant to ARF. In addition, the maternal nephrotoxic medications used in complicated pregnancies may enter the fetal circulation and contribute to renal injury.

Laboratory Markers in the Differential Diagnosis

The differential diagnosis of various types of ARF based on urinary excretion patterns is summarized in Table 2. In prerenal (dehydration) ARF, the urine osmolality is elevated to more than 500 mOsm/kg because the renal tubule is reabsorbing all the filtered volume that it can. In acute renal tubular injury causing ARF, the renal concentrating ability is impaired, resulting in low urine osmolality of less than 350 mOsm/kg. Thus, it is important in the evaluation of ARF to obtain a spot urine for determination of urine osmolality before various treatments compromise the usefulness of this test. However, use of these indices is complicated by considerable overlap in urinary osmolality, urea, creatinine, and sodium. Thus, the best strategy for the combined use of these indices remains unclear. It has been suggested that the so-called kidney failure index (KFI) (urine sodium divided by the urine-to-plasma creatinine ratio) be used to differentiate the four categories of ARF (Table 2), with a KFI of higher than 1 designating renal and a KFI of less than 1 designating prerenal azotemia.

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TABLE 2.

Differential Diagnosis of Acute Renal Failure Using Urinary Indices in Neonates (N) and Children (C)

The fractional excretion of sodium (FE_Na) is just as useful. The FE_Na, calculated as the ratio of urine to plasma sodium divided by the ratio of urine to plasma creatinine, is less than 1% in prerenal azotemia; an FE_Na greater than 2% supports the diagnosis of ARF. In preterm infants, an FE_Na less than 2.5% suggests prerenal azotemia.

In the neonate, the KFI is higher than 2.5 in renal and less than 2.5 in prerenal azotemia. It should be recognized that glomerular filtration rates (GFRs) are lower in preterm neonates compared with term infants and older children (Table 3). The normal serum creatinine also varies with age, with higher values related to higher muscle mass in older children (Table 4).

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TABLE 3.

Normal Glomerular Filtration Rate Values for Children

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TABLE 4.

Normal Serum Creatinine Concentrations at Different Ages

Treatment

Emergency Fluid Management.

ARF (including the high-output variety) due to ischemic or toxic shock is managed best in the pediatric intensive care unit (PICU). Once kidney failure is established, fluid management should be guided by the principles of replacing the estimated insensible water loss (IWL) plus the loss in both volume and electrolytes from urinary or other outputs.

The increased endogenous water production of 100 mL/m² per day resulting from increased tissue catabolism in uremia must be subtracted from the IWL of 400 mL/m² per day. Thus, the IWL calculations in ARF compute to 300 mL/m² per day, not the IWL of 400 mL/m² per day under normal circumstances. Urine output should be replaced (volume for volume) with intravenous fluid solutions of approximately the same electrolyte composition as that of the urine. For this purpose, the sodium and potassium content of the urinary output should be analyzed.

The success of ARF management depends on meticulous monitoring of daily urine and other outputs and careful restoration of caloric, fluid, and electrolyte losses. A daily weight loss of up to 1% of the body weight is expected during the management of the initial oliguric phase of ARF. Weight gain or hyponatremia during this period usually indicates fluid overload.

Furosemide (administered intravenously at 1 mg/kg) promotes renal blood flow and acts as a renoprotective agent in the early stages of ARF.

Caloric Management.

A minimum of 25% of the daily caloric requirement must be supplied to reduce the catabolism of ARF. This can be achieved by a 25% dextrose solution delivered via an indwelling cannula inserted into the superior vena cava to avoid peripheral venous thrombosis from such a hypertonic solution. Intravenous infusion of essential amino acids has been advocated as therapy for patients who have ARF, based on the theory that accumulations of urea, creatinine, potassium, and phosphate are removed in the synthesis of nonessential amino acids from essential amino acids and the formation of new tissue. Paradoxically, when essential amino acids are infused, these variables increase significantly. Thus, the use of essential amino acid in ARF has not gained much acceptance.

The oliguric phase of ARF usually lasts from a few days to 2 weeks. A popular high-caloric supplement, given when the child regains his or her appetite (toward the end of that period) is corn syrup in ginger ale or lemon juice.

Hyperkalemia and Hyponatremia.

A number of treatment complications may occur during the oliguric phase. Hyperkalemia (>6.5 mEq/L [6.5 mmol/L]), with T-wave elevation on electrocardiogram (ECG) examination, requires prompt treatment with one or a combination of the following maneuvers: 1) infusion of 0.5 mL/kg of 10% calcium gluconate solution over 2 to 4 minutes with stethoscopic or ECG monitoring of the heart; 2) intravenous crystalline insulin at 1 U of insulin in 5 g dextrose to promote movement of potassium intracellularly through enhanced gluconeogenesis, monitored by serial blood glucose determinations; or 3) kayexalate cation exchange resins at a dose of 1 g/kg body weight in a 20% sorbitol or dextrose solution, administered either as a high-retention enema or orally, to help rid the potassium burden from the body.

Hyponatremia (<130 mEq/L [130 mmol/L]), which almost invariably results from fluid overload, must be corrected promptly by fluid restriction.

Metabolic Acidosis and Other Complications.

Other complications of ARF include metabolic acidosis, seizures, and such clinical entities as pericarditis, infection, and anemia. Metabolic acidosis results from impairment of renal net acid excretion and requires judicious use of sodium bicarbonate therapy when the serum total bicarbonate falls below 10 mEq/L (10 mmol/L). At the other extreme of acid-base disturbance, metabolic alkalosis can develop from the combined loss of hydrochloric acid and potassium depletion from nasal gastric suction. Seizures may occur in an oliguric child because of hypokalemia, hypertension, hypocalcemia, or the rapid elevation of blood urea nitrogen. Each of these specific causes should be sought and the appropriate treatment instituted. Seizures from other causes can be controlled with slow intravenous infusion of diazepam at 0.1 mg/kg, followed by maintenance therapy with diphenylhydantoin at dosages of 3 to 8 mg/kg orally.

Decision to Dialyze.

Peritoneal or hemodialysis should be considered when any of the complications become severe, as represented by the following conditions: 1) serum urea nitrogen in excess of 150 mg/dL (53.6 mmol/L); 2) serum creatinine in excess of 10 mg/dL (884 mcmol/L); 3) potassium in excess of 6.5 mEq/L (6.5 mmol/L), with T-wave elevation on ECG unrelieved by medical means; 4) severe metabolic acidosis with serum bicarbonate persistently below 10 mEq/L (10 mmol/L) and unrelieved by bicarbonate therapy; and 5) congestive heart failure and fluid overload. The serum urea nitrogen can be expected to be reduced by at least 50% within 48 hours of the institution of peritoneal dialysis; serum potassium can be expected to fall to a normal range and metabolic acidosis to be reversed within 24 hours. Hemodialysis achieves these ends at a fraction of the time of peritoneal dialysis. If vascular access is available, hemodialysis is now the preferred dialysis modality in North American PICUs. In developing countries, peritoneal dialysis has the advantages of lower cost and no dependency on expensive hemodialysis machinery.

Continuous veno-venous hemofiltration (CVVH) is especially useful in hemodynamically unstable patients in PICUs. CVVH is comparable to intermittent hemodialysis, although a recent retrospective study indicated a lower survival rate among patients treated with CVVH.

Growth Hormone and Insulin-like Growth Factor.

Despite initial claims of increasing renal blood flow, the use of either recombinant human growth hormone or insulin-like growth factor in ARF has not improved survival or resulted in demonstrable alleviation of significant renal injury. Thus, their continued use in treating ARF is being called into question.

Outcome

There are three phases in the course of ARF: the oliguric phase, the diuretic phase, and the recovery phase. Each of the oliguric and diuretic phases usually lasts a few days to 2 weeks. With conservative management, the diuretic phase of ARF usually begins 7 to 14 days after the onset of oliguria. However, blood urea nitrogen and serum potassium levels may continue to rise during the first few days of diuresis, possibly because the intracellular urea and potassium that have accumulated during oliguria are moving into the extracellular compartment. Daily body weight, precise intake and output volumes, and urinary losses of electrolytes and fluids must be monitored continuously and these losses scrupulously replaced during the diuretic phase. Seizures, urinary tract infections, and psychoses are not uncommon during the diuretic phase. The recovery phase may vary from a few weeks to several months for all urinary abnormalities (eg, hematuria and proteinuria) to disappear.

The expected overall survival rate for children who have ARF is 70%. The 30% mortality usually is due to secondary complications, such as sepsis.

Chronic Renal Failure

Incidence and Causes

CRF affects nearly 500/1 million population per year; 1% to 2% are in the pediatric age range. The provision of dialysis and transplantation for these individuals in the United States costs $15.64 billion, with 75% of the total cost paid by the United States Treasury via Medicare. (These data are from 1997, the latest year in which the data analysis was completed by the United States Renal Data System, and are available in the August 1999 issue of the American Journal of Kidney Diseases.) Despite ongoing debate concerning treatment availability and costs, the industrialized nations of the world have affirmed government support for these treatments for the immediate future, despite worldwide fiscal constraints on health care expenditures. The aims of the next decade must be focused on optimizing the medical management of chronic renal diseases to improve the quality of life, slow the rate of progression of renal disease, and alleviate the tax burden. In children, the future aims also must include maximizing growth and development. Table 5 summarizes the causes of CRF in children.

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TABLE 5.

Percent Distribution of Primary Renal Disease in Children Resulting in Renal Transplantation

Clinical Presentation: The Four Stages of Chronic Renal Disease

The first stage of chronic renal disease coincides with a GFR of 50% to 75% of normal for age. This is an asymptomatic stage. Increases in serum urea nitrogen, creatinine, and parathyroid hormone ensue only after the GFR falls below 50% of normal. The second stage of chronic renal disease generally is referred to as chronic renal insufficiency and coincides with the GFR of 25% to 50% of normal for age. Heavy, asymptomatic proteinuria of more than 1,000 mg/d often is present. Hyposthenuria and nocturia also are characteristic features. Whereas infection and dehydration seldom cause significant problems in the first stage because of a wider margin of renal functional reserve, these conditions may precipitate severe azotemia in the second stage. The third stage of chronic renal disease, generally known as CRF, is related to a GFR of 10% to 25% of normal and is characterized by the clinical features of anemia, acidosis, hyperphosphatemia, and hypocalcemia as well as renal osteodystrophy and rickets. The fourth and final stage of chronic renal disease, known as end-stage renal disease, coincides with the GFR of less than 10% of normal. Because of the severe neurologic, cardiovascular, intestinal, hematologic, and skeletal abnormalities that usher in this final stage, preparation for the initiation of dialysis and transplantation must begin as the child enters the transition into end-stage disease. Although the first two stages of CRF are distinct, the features of the last two stages overlap.

Reversible Renal Failure

Chronic renal disease is slowly progressive. Depending on the underlying cause, it may progress over the course of a dozen years or longer to end-stage renal disease. The first two stages of CRF (vide supra) often are asymptomatic, but functional impairment is accelerated by various reversible causes (eg, dehydration, hypertension, congestive heart failure, hypercalcemia, hyperuricemia, hypokalemia, alkalosis, and nephrotoxic agents including certain antibiotics, cyclooxygenase inhibitors, converting enzyme inhibitors, and nonsteroidal anti-inflammatory agents). Persistent metabolic alkalosis in association with diuretic-induced hypokalemia may be early clues of interstitial nephritis. If the diagnosis is established and the appropriate treatment instituted, accelerated deterioration of renal function could be reversed. Dehydration and salt depletion exacerbate chronic renal insufficiency. Hypercalcemia impairs renal function. Early recognition and treatment of these defects should alleviate further immediate renal damage. The control of hypertension limits arteriolar nephrosclerosis and retards the rate of renal function deterioration. Hyperuricemia gives rise to renal tubular deposition of uric acid crystals. Early recognition and treatment by alkalinization of the urine or by the use of allopurinol may preserve renal function.

Patients who have CRF not only have depressed renal function, but they also are predisposed to urinary tract infections, which must be treated promptly with the appropriate antibiotics to conserve the marginal renal reserve. The physician must guard against such reversible deterioration of renal function, thereby conserving residual function. In vivo studies have shown that antioxidants (eg, acetylcysteine) prevent injury from radiocontrast agents. Just as importantly, animal studies have demonstrated that antioxidants (eg, alpha-tocopherol) reverse renal injury in progressive renal diseases. Buddhist monks who had CRF and ate one low-protein vegetarian meal per day demonstrated a slower rate of progression to end-stage renal failure than did controls. However, such studies are faulted for methodologic difficulties, including the lack of renal histologic evaluation of the study groups. Treatments to slow the progression of CRF are summarized in Table 6.

Major Complications

As the kidney fails, major disturbances in calcium, phosphate, and acid-base metabolism develop, resulting in renal rickets and growth retardation. With the increasing recognition of the kidneys as an endocrine organ, CRF can be said to give rise to malfunctions of all endocrine systems. The lack of erythropoietin production associated with kidney failure results in anemia. Insulin resistance, thyroid, and other endocrine dysfunctions complicate CRF. Growth hormone resistance in uremia, coupled with renal osteodystrophy, contributes to the often severe growth failure seen in children who have CRF. Anorexia frequently complicates the late stages, resulting in nutritional deficiency. These and related complications of CRF are reviewed to provide the pediatrician with a better understanding of how to help the child who has this major organ failure and to address the family’s concerns.

Renal Osteodystrophy.

Figure 1 illustrates the three major consequences of CRF. The first is impaired phosphate excretion, which results in an elevation of serum phosphate and a reciprocal drop in calcium, stimulating the development of secondary hyperparathyroidism and renal osteodystrophy. The second and probably major consequence of CRF on calcium metabolism is the impaired formation of active metabolites of vitamin D, resulting in malabsorption of calcium across the intestinal tract, giving rise to hypocalcemia. With uremia, there is increasing evidence of a skeletal parathyroid hormone resistance, which also contributes to the development of secondary hyperparathyroidism. Finally, the third major consequence of CRF is the impaired excretion of net acid and retention of urea. The resultant development of metabolic acidosis and uremia contributes to skeletal parathyroid hormone resistance and also may contribute directly to the development of renal osteodystrophy. The signs and symptoms of renal osteodystrophy are summarized in Table 7.

FIGURE 1.

Chronic renal failure leading to major consequences in calcium and phosphate metabolism and the development of renal osteodystrophy.

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TABLE 6.

Slowing the Progression of Chronic Renal Failure

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TABLE 7.

Clinical Features of Renal Osteodystrophy in Childhood

Growth Failure.

Growth hormone is secreted from the anterior pituitary (Fig. 2), but it does not exert a growth effect directly at the target site, except in the liver, where it stimulates the formation of insulin-like growth factor-1 (IGF-1), previously known as somatomedin C. IGF-1 acts as a paracrine hormone at the growth plate of the long bone to stimulate growth, augmented to a small degree by growth hormone directly. Feedback regulation to the further secretion of growth hormone is negative.

FIGURE 2.

Growth hormone (GH) and insulin-like growth factor-1 (IGF-1) axis. Action of GH on hepatic production of IGF-1. Negative feedback regulation to the further secretion of GH is represented by the interrupted lines. From Krieg RJ Jr, Santos F, Chan JCM. Growth hormone, insulin-like growth factor, and the kidney. Kidney Int. 1995;48:321–336. By permission of International Society of Nephrology.

FIGURE 3.

Sequence of initiation of treatment modalities in relation to the progressive decline in glomerular filtration rate (GFR) at % of normal for age.

Tissue resistance to endogenous and exogenous growth hormone has been documented carefully in recent studies showing that the expression of IGF-1 in uremia is significantly blunted compared with that of control and pair-fed animals. Growth hormone receptor mRNA also is inhibited by the uremic condition. The increased IGF-binding proteins encountered in CRF also interfere with growth hormone action. Thus, the use of recombinant human growth hormone for treatment of growth disturbance due to CRF now can be defended based on the rationale of the need to overcome such clearly demonstrated tissue resistance.

The majority of children who have CRF suffer from significant growth retardation. Recombinant human growth hormone augments linear growth in children who have chronic renal insufficiency, with the potential for 3 to 4 inches of additional growth over 2 years. Despite concerns about the possibility of hypercalciuria associated with conjoint use of calcitriol and recombinant human growth hormone in uremic animals and the risk of focal glomerulosclerosis in growth hormone transgenic mice experiments, the use of conventional doses of recombinant human growth hormone (0.3 IU/kg per week) has been found to be safe and efficacious. No increased risk of malignancy has been encountered with use of recombinant human growth hormone in CRF over the past decade.

Anemia.

When renal function falls below 15% of normal for age, anemia appears with increasing frequency in children who have CRF. Table 8 summarizes the multiple factors contributing to the pathogenesis of the normocytic, normochronic anemia that characterizes CRF. To prevent nutritional anemia due to folate deficiency, oral supplementation with folic acid 1 mg/d is recommended. In addition, if serum ferritin levels are low, oral iron supplementation is required. Recombinant human erythropoietin at 50 to 100 IU/kg per week to reverse anemia usually becomes necessary in those undergoing dialysis.

Metabolic Acidosis and Growth Failure.

Increased proteolysis occurs in response to a relatively small decrease in serum bicarbonate from 20 mEq/L to 17 mEq/L. More importantly, the recognition that metabolic acidosis inhibits growth hormone pulsatile secretion and expression has led to the recommendation by the Kidney Foundation (K/DOQ1 2000) that serum bicarbonate be maintained at 22 mEq/L with bicarbonate therapy (Table 9).

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TABLE 8.

Pathogenic Factors of the Anemia of Chronic Renal Failure

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TABLE 9.

Oral Preparations for Alkali Therapy

Nutrition Deficiencies in Growth Failure.

The importance of energy intake on growth is illustrated by the significant correlation between growth velocity (expressed as percentage of normal) and energy intake (expressed as percentage of that recommended for age). Reduced growth velocity almost invariably is present in children who have uremia and an energy intake below 80% of the recommended dietary allowance. Caloric intake should be maintained at the recommended dietary allowance for healthy children of the same height and age (Table 10). These calories should be provided as carbohydrate (50%) and fat (40%), with protein kept to only 10% of the total.

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TABLE 10.

Estimated Safe and Adequate Daily Dietary Intake for Calories, Protein, Sodium, Potassium, Calcium, and Phosphorus in Chronic Renal Insufficiency

Caloric and Nutrient Maximization of Growth in Infancy.

Infants who have early chronic renal insufficiency grow poorly. However, dialysis and transplantation in such infants do not result in catch-up growth. Abitbol et al demonstrated that nutritional deficiencies are pivotal contributors to this growth failure. With vigorous caloric and protein supplementations to reach close to 100% of the recommended dietary allowance, weight gain without linear growth acceleration was demonstrated. Improvement in body mass indices did not extend to length and head circumference. For this reason, it was recommended that protein intake in infants be restricted to 75% of the recommended dietary allowance to minimize protein waste product accumulation in CRF.

Despite early treatment with vitamin D metabolites, the elevated parathyroid hormone concentration in these infants correlated inversely with linear growth, suggesting that better treatment of subclinical bone disease is essential in infancy.

Carbohydate, Lipid, Nitrogen Disorders.

The glucose intolerance in uremia is associated with peripheral insulin resistance. Elevated serum cholesterol and triglyceride and reduced high-density lipoprotein cholesterol levels may be related to this dysfunction in carbohydrate metabolism.

The retention of nitrogenous products results in anorexia, nausea, vomiting, and uremic stomatitis, but no specific agent or single “uremic toxin” has been identified to account for these symptoms of the uremic syndrome

Other Systemic Disorders.

Impaired immunologic defenses and delayed wound healing give rise to a higher incidence of infection in uremic patients. A progressive encephalopathy, developmental delay, seizures, myoclonus, hypotonia, ataxia, and chorea have been noted in infants who have CRF. Uremic encephalopathy in a child or adult presents with nonspecific complaints (eg, listlessness, fatigue, depression), with late signs consisting of myoclonus, slurred speech, confusion, seizures, and psychosis. Uremic peripheral neuropathy is distal and symmetric.

The incidence of duodenal ulcers is increased in those who have uremia, which may be related to a rise in serum gastrin concentration due to inadequate excretion by the failing kidney. Pericardial effusion and pericarditis may occur at a higher frequency when the serum urea nitrogen concentration exceeds 80 mg/dL. Uremic pneumonia is an extreme form of pulmonary edema. Pulmonary edema may follow fluid overload and left heart failure from malignant hypertension.

Sexual dysfunction follows decreased concentrations of follicle-stimulating hormone and testosterone in CRF. The pruritis of uremia is due to microscopic subcutaneous calcium deposition associated with secondary hyperparathyroidism. If orally administered diphenhydramine 10 to 25 mg two to three times per day (maximum, 300 mg/d) fails to alleviate the pruritis, the final resort is parathyroidectomy, which may alleviate this symptom.

Recommendations

CRF progresses in an orderly fashion; when 25% to 50% of the renal functions are lost, secondary hyperparathyroidism can be expected in most children (Fig. 3). When kidney functions are reduced to 50%, parathyroid hormone concentrations will be elevated. Thus, secondary hyperparathyroidism invariably is present at 50% reduction in GFR, warranting the use of calcium carbonate as a phosphate binder and dihydrotachysterol (DHT) or calcitriol (1,25-dihydroxyvitamin D₃) or the nonhypercalcemic vitamin D metabolite 22-oxacalcitriol to control the secondary hyperparathyroidism. When only 30% of the normal GFR remains (with rising serum urea nitrogen and creatinine and hypertension), protein and salt restriction, multiple vitamins, antihypertensives, and diuretics should be introduced into the treatment regimen. At 5% to 10% of normal GFR, nausea and vomiting from the uremia require treatment with antiemetics, and planning for dialysis and kidney transplantation must begin.

In children who have CRF, the standard of care now consists of using DHT 0.01 mg/kg per day or calcitriol (1,25-dihydroxyvitamin D₃) to treat the renal osteodystrophy, suppress the hyperparathyroidism, and promote linear growth. DHT is available in liquid droplets and can be calibrated more easily for use in infants. Calcitriol is available only in 0.25 and 0.5 mcg capsules. Aluminum hydroxide should be avoided because the aluminum may be absorbed through the gastrointestinal tract in the presence of hyperparathyroidism and uremia. Calcium carbonate 20 mg/kg per day is an excellent phosphate binder that also provides additional calcium intake and is mildly alkalogenic. It is important to use a higher dosage of calcium carbonate with the major meals (eg, dinner) to bind the increased amounts of phosphate. Sevelamer hydrochloride, a new and effective phosphate binder, as well as calcium acetate are gaining patient acceptance due their improved taste. Alkali therapy (Bicitra 2 mEq/kg per day in two to three divided doses, Table 9 should be used to correct metabolic acidosis and reduce proteolysis due to acidosis.

Protein should be restricted to 0.8 to 2.2 g/kg per day, according to the age, body weight, and gender (Table 10). Energy provisions should be 38 to 42 kcal/kg per day in females and males 15 to 18 years of age and as high as 100 kcal/kg per day in those between 1 and 3 years of age (Table 10). Phosphate should be restricted to generally less than 12 mg/kg per day.

Recombinant human growth hormone should be administered at 0.05 mg/kg per day before renal transplantation. This therapy is stopped when the child attains the 50th percentile for midparental height or receives a kidney transplant.

Nonpharmacologic antihypertensive therapy consists of weight control, exercise, stress reduction, and dietary sodium restriction. Such lifestyle changes need the participation of the entire family to succeed.

Pharmacologic antihypertensive therapy may employ a host of new medications to suppress the renin-angiotensin system (Table 11) as well as old, well-tested medications such as diuretics, which reduce the volume expansion of CRF. Diuretics lose their effectiveness in CRF when 70% of renal function is lost because of the inability to increase distal tubular sodium delivery and free water loss.

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TABLE 11.

Selected Antihypertensive Drugs for Children Who Have Chronic Renal Failure

Generally, anemia significant enough to require blood transfusions or erythropoietin is not encountered until the GFR is less than 10 mL/min per 1.73 m², which usually is only after the patient enters into the dialysis program. At this time, recombinant human erythropoietin at 50 to 100 IU/kg per week is an important therapeutic maneuver to reverse the normochromic, normocytic anemia. Because of the rapid formation of red cells after recombinant human erythropoietin administration, serum transferrin concentrations need to be followed, and if the serum transferrin saturation is less than 20%, iron supplementation at 0.5 mg/kg per day should be initiated. In many centers, iron always is administered with erythropoietin therapy.

The rate of progression of kidney failure can be slowed with careful dietary control, judicious protein restriction, a low-phosphate diet, reduction of glomerular hyperfiltration by converting enzyme inhibitor, and control of systemic hypertension.

Prognosis in End-stage Renal Failure

Coincidental to a GFR of less than 10% of normal for age, when conservative management of CRF reaches its limits, dialysis and transplantation become the next therapeutic modalities. In the past 2 decades, continuous ambulatory peritoneal dialysis (CAPD) and continuous cycling peritoneal dialysis (CCPD) have gained wide acceptance as the dialysis modalities of choice for children.

In contrast to the usual peritoneal dialysis in which the dialysate dwells in the peritoneal space for 30 minutes, the “dwell” time in CAPD is usually 4 to 8 hours. Thus, the dialysis exchanges are minimized to four or five per day. Besides the advantage of costing less than hemodialysis, CAPD usually is performed at home (after a 2-week training course) without expensive equipment or interference with the child’s schooling. The principal disadvantage is the unreasonably high frequency of peritonitis (averaging two episodes per year) attributed to inadvertent breakdowns in sterile techniques.

Although the long-term prognosis for patients receiving CAPD is not yet available, the long-term survival rates for children undergoing chronic hemodialysis and renal transplantation are. Of children receiving long-term chronic hemodialysis, all survived at 6 months and 95% at 5 years. Of living-related transplantations in all age groups, 92% survived at 6 months and 72% at 5 years, with allograft half-lives of 13 years. For cadavaric transplantations, survival was 86% at 6 months and 65% at 5 years, with allograft half-life of 9 years. In contrast to live unrelated organ donors, parent donor transplants do significantly better than cadaveric transplants. Survival is 74% at 5 years, and allograft half-life is 12 years. Over the years, kidney transplants have improved due to the many new and powerful antirejection medications.

Dialysis and transplantation in infants and children, with cumulative experience over the past 3 decades, have become widely accepted treatments in end-stage renal disease.

Acknowledgments

The authors thank Betty Timozek for secretarial support and K. C. Lin, MSc, for library research. Supported by National Institutes of Health grant T32 07761.