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BACKGROUND

Failure to thrive (FTT) is among the most challenging diagnostic entities facing pediatric hospitalists. The interaction of psychosocial, behavioral, and physiologic factors can be tremendously complex. Because there is no uniformly accepted definition for FTT, the incidence cannot be precisely determined. However, in high-risk populations (low-birth weight infants, children living in poverty), estimates run as high as 5% to 10%. While the disorder is primarily managed in the outpatient setting, more challenging or severely affected patients or those whose safety is in question may require hospitalization. Thus it is critical for pediatric hospitalists to have a clear approach to this diagnostic challenge.

FTT is not a diagnosis, but rather a description of undernutrition and deficient growth over time. Due to the vagueness of the term, many specialists have suggested that it be replaced by a term such as “growth deficiency,” “growth failure,” or “undernutrition.” To date, no one of these terms has fully taken hold, but each may be used interchangeably with FTT.

Growth failure can occur at any age. However, due to the vulnerability of infants and toddlers and their complete dependence on caregivers for nutrition, it is most commonly noted in the youngest age groups. Approximately 80% of cases involve infants less than 6 months of age; over 95% of patients are under the age of 2.

PATHOPHYSIOLOGY

The etiology of FTT is frequently multifactorial. While the list of possible organic causes is quite long, psychosocial and behavioral factors play the predominant role in the majority of cases. This is particularly true in patients under 2 years of age.

It is useful to recognize that inadequate growth can be caused by any combination of three factors: (1) abnormally low caloric intake, (2) inadequate digestion and absorption of ingested calories, and (3) abnormally high metabolic demands or impaired utilization of calories.

In the early stages, undernutrition may have little obvious consequence to the child. However, more severe or longstanding cases may lead to short stature, reduced muscle mass, impaired brain growth, and behavioral or developmental abnormalities. Marasmus and kwashiorkor, caused by extreme malnutrition, are rarely seen in the United States.

DEFINITIONS

There is no consensus definition for FTT. It is commonly defined as patient weight below the 5th percentile or a downward change in growth rate that results in the crossing of two major percentile lines for weight. Additionally, weight for height or height for age below the 10th percentile have been used as indicators of deficient growth. These rigid criteria, however, greatly oversimplify the complex task of identifying children in whom growth is truly a problem. As many as 25% of normal infants will cross major percentile lines during their first 2 years of life, then maintain growth consistently along their new curve. Most of these children show no signs of illness and should not be categorized as ...

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