The databases mentioned previously have confirmed that children with chronic renal disease present in a different manner from similarly affected adults (Box 322.1). The adult patient with reduced renal function may develop hypertension, edema, and nocturia, but the uremic syndrome is the hallmark of renal failure in most adults. The uremic syndrome includes such nonspecific symptoms as lethargy, drowsiness, itching, nausea, vomiting, and paresthesias. Although at times the pediatrician sees these late symptoms, for the child with renal insufficiency, an earlier establishment of the diagnosis and initiation of therapy, when subtler symptoms occur, is advantageous.

The most common finding that should alert the pediatrician to the possibility of CRD is impairment of growth. The mean height of children entering the NAPRTCS CRI database is 1.49 standard deviations (SDs) below the mean. For the NAPRTCS dialysis database, mean height at entry is 1.69 SD below the mean. Short stature, particularly if associated with other symptoms, such as polyuria, frequent bouts of dehydration, salt craving, bone deformities, abnormal tooth development, or anemia, should suggest that the affected patient may have CRD. A previous history of urinary tract infections, nephrotic syndrome, or glomerulonephritis adds further support to this suspected diagnosis.

The nomenclature describing stages of CRD is confusing. The currently accepted definitions are listed in Table 322.1. The term impaired renal function usually refers to an individual who is asymptomatic and has a residual renal function of 40% to 80% of normal. The term CRI is associated with a residual function of 25% to 50% of normal. At this level of renal function, distinct biochemical abnormalities may be present only when the patient is stressed. For example, the patient normally may maintain acid–base balance but, with stress, develop acidosis. Although serum calcium and phosphorous levels are normal, they remain so at the expense of an elevated serum parathyroid hormone. The child with CRI may develop dehydration early in the course of diarrhea because of reduced renal ability to retain sodium. With this degree of renal impairment, growth is slowed, and, although dialysis is not needed, aggressive therapy is indicated.

The term chronic renal failure (CRF) is used to describe a patient who has residual renal function of less than 30%. The patient with CRF exhibits biochemical abnormalities even when not stressed. This patient usually has renal osteodystrophy, acidosis, and anemia; hypertension may be present. Vigorous therapeutic regimens may or may not successfully control these biochemical abnormalities.

ESRD is a term reserved for that stage of disease when renal replacement therapy, whether dialysis or transplantation, is required. The degree of renal function at which dialysis or transplantation is required varies and depends on many factors, including the cause of renal failure, age of the patient, and the patient’s compliance with conservative therapy. Uremia is a symptom complex that includes anorexia, nausea, itching, neuropathy, and malaise. This complex is not associated with any specific concentration of urea in the blood, but it usually is considered to be the last stage of renal failure.

The etiologies of CRF in children are listed in Box 322.2. The NAPRTCS registry confirms that different forms of obstructive uropathy (including reflux and dysplasia) account for almost 50% of the etiologies of renal failure in children. Other relatively common causes of ESRD in children that are rare in adults include renal hypoplasia and dysplasia, hereditary nephritis, infantile polycystic disease, cystinosis, and uremic medullary cystic disease. Focal glomerulosclerosis is the most common glomerulopathy leading to renal failure in young children (accounting for 14.8% of all children with ESRD), but older children may suffer from many forms of chronic glomerulonephritis.