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.

Few conditions better illustrate the value of a careful history than FTT (Table 23-1). Because so many cases of FTT are attributable to behavioral and psychosocial factors, the first step in evaluating the condition is to obtain a detailed feeding history. This must include details of the child’s diet (frequency, content, how formula is mixed, excessive juice or milk), feeding environment (supervision, distractions, feeding position), and feeding behavior (distractibility, food refusal, early satiety). For breastfed infants it is important to assess the frequency and duration of feedings and whether the baby is feeding and swallowing vigorously. After completion of a feeding, a mother should typically note that her breasts feel softer and less full. The frequency and volume of urine and stool output also lend insight to the quantity of intake. Familial growth patterns should be assessed. In addition, a detailed social history is critical. Key areas to explore include major stressors in the home, financial difficulties including food insecurity, depression, substance abuse, domestic violence, and history of prior Child Protective Service reports. The remainder of the history is directed toward eliciting symptoms suggestive of underlying organic disease.

A directed physical examination (Table 23-2) should begin with carefully obtained weight, length, and head circumference. For children from 0 to 2 years old, these measurements should be plotted on the 2006 WHO growth standards charts, which were developed using longitudinal data from breastfed children in several developed countries. For children over 2 years old, the data can be plotted on the 2002 CDC growth charts. Several syndrome-specific growth charts are available on which to plot anthropometric measurements for children with known inherited disorders (e.g. trisomy 21). In addition to plotting these parameters individually, comparison of the measurements may provide insight into the chronicity or etiology of the process. Initially, undernutrition causes an isolated slowing of weight gain. With more longstanding nutritional deficiency, height velocity also slows, while head growth is typically spared until the problem has become severe and longstanding. Endocrinopathies may manifest as synchronous slowing of height and weight, while underlying metabolic or neurologic disorders may manifest microcephaly.