• Persistent weight loss over time.
  
• Growth failure associated with disordered behavior and development.
  
• Weight less than third percentile for age.
  
• Weight crosses two major percentiles downward over any period of time and continues to fall.
  
• Median weight for age of 76%-90% (mild undernutrition), 61%-75% (moderate undernutrition), or <61% (severe undernutrition).

Failure to thrive (FTT) is an old problem that continues to be an important entity for all practitioners who provide care to children. Growth is one of the essential tasks of childhood and is an indication of the child’s general health. Growth failure may be the first symptom of serious organ dysfunction. Most frequently, however, growth failure represents inadequate caloric intake. Malnutrition during the critical period of brain growth in early childhood has been linked to delayed motor, cognitive, and social development. Developmental deficits may persist even after nutritional therapy has been instituted.

FTT was first described by Holt in 1897; he describes a group of children who suddenly “ceased to thrive” and became “wasted skeletons” when weaned after the first 4-6 weeks of life. More than 100 years later there is no consensus definition of FTT. Residents and medical students need to be familiar with several definitions of FTT. Practitioners must also recognize the limitations of each definition. Competing definitions of FTT include the following:

• Persistent weight loss over time. Children should steadily gain weight. Weight loss beyond the setting of an acute illness is pathological. However, the assessment and treatment for FTT need to be addressed before the child has had persistent weight loss.
  
• Growth failure associated with disordered behavior and development. This old definition is useful because it reminds the practitioner of the serious sequelae and important alarm features in children with undernutrition. Currently, FTT is more commonly defined by anthropometric guidelines alone.
  
• Weight less than the third percentile for age. This is a classic definition. However, this definition includes children with genetic short stature and children whose weight transiently dips beneath the third percentile with an intercurrent illness.
  
• Weight crosses two major percentiles downward over any period of time. Thirty percent of normal children will drop two major percentiles within the first 2 years of life as their growth curve shifts to their genetic potential. These healthy children will continue to grow on the adjusted growth curve. Children with FTT do not attain a new curve, but continue to fall. The most accurate assessment for failure to thrive is a calculation of the child’s median weight for age. This quick calculation enables the clinician to assess the degree of undernutrition and plan an appropriate course of evaluation and intervention. The median weight for age is determined by the United States Centers for Disease Control and Prevention (CDC) growth charts. The median should not be adjusted for race, ethnicity, or country of origin. Differences in growth are more likely due to inadequate nutrition in specific geographic or economically deprived populations. Determinations of nutritional status are as follows:
  
  
  
  • Seventy-six to 90% median weight for age represents mild undernutrition. These children are in no immediate danger and may be safely observed over time (Table 2-1).
    
  • Sixty-one to 75% median weight for age is moderate undernutrition. These children warrant immediate evaluation and intervention with close follow-up in an outpatient setting.
    
  • Less than 61% median weight for age is severe undernutrition. These children may require hospitalization for evaluation and nutritional support.

FTT is one of the most common diagnoses of early childhood in the United States. It affects all socioeconomic groups, but children in poverty are more likely to be affected and more likely to suffer long-term sequelae. Ten percent of children in poverty meet criteria for FTT. As many as 30% of children presenting to emergency departments for unrelated complaints can be diagnosed with FTT. This group of children is of most concern. They are least likely to have good continuity of care and most likely to suffer additional developmental insults such as social isolation, tenuous housing situations, and neglect. Because FTT is most prevalent in at-risk populations that are least likely to have good continuity of care it is crucial to address growth parameters at every visit, both sick and well. Many children with FTT may not present for well child visits: if that is the only visit at which the clinician considers growth, many opportunities for meaningful intervention may be lost.

When diagnosing FTT it is essential to consider the etiology. Historically there has been a dichotomy: organic versus nonorganic FTT. Either children had major organ dysfunction (organic) or psychosocial problems led to inadequate nutrition (nonorganic). Over the past decades FTT has been better understood as a mixed entity in which both organic disease and psychosocial factors influence each other. With this understanding, the old belief that a child who gains weight in the hospital has nonorganic FTT has been debunked.

Organic FTT

Organic causes are identified in 10% of children with FTT. In-hospital evaluations reveal an underlying organic etiology in about 30% of children. These data are misleading, however. More than two-thirds of these children are diagnosed with gastroesophageal reflux disease (GERD). The practitioner risks one of two errors in diagnosing GERD as the source of failure to thrive: physiological reflux is found in at least 70% of infants. It may be a normal finding in an infant who is failing to thrive for other reasons. Further, undernutrition causes decreased lower esophageal segment (LES) tone, which may lead to reflux as an effect rather than a cause of FTT.

Nonorganic FTT

Nonorganic FTT, weight loss in which no physiological disease is identified, constitutes 80% of cases. Historically, the responsibility for this diagnosis fell on the caretaker. Either the parent was unable to provide enough nutrition or the parent was emotionally unavailable to the infant. In either circumstance the result was unsuccessful feeding. Psychosocial stressors were thought to create a neuroendocrine milieu preventing growth even when calories were available: increased cortisol and decreased insulin levels in undernourished children inhibit weight gain.

Mixed FTT

Most FTT is neither purely organic nor nonorganic, but rather mixed: there is a transaction between both physiological and psychosocial factors that creates a vicious cycle of undernutrition. For example, a child with organic disease may initially have difficulty eating for purely physiological reasons. However, over time, the feedings become fraught with anxiety for both parents and child and are even less successful. The child senses the parents’ anxiety and eats less and more fretfully than before. The parents, afraid to overtax the “fragile” child, may not give the child the time needed to eat. They may become frustrated that they are not easily able to accomplish this most basic and essential care for the child. Parents of an ill child may perceive that other aspects of care are more important than feeding, such as strict adherence to a medication or therapy regimen.

Children with organic disease underlying FTT often gain weight in the hospital when fed by emotionally uninvolved parties such as nurses, volunteers, or physicians: these people do not feel that the child’s difficulties represent personal failure and may be more patient. They are also not the sole providers for all of the child’s needs. This happy circumstance (weight gain in the hospital) should not be mistaken for parental neglect in the home; rather, the primary care provider should pay close attention to the psychosocial stressors on the feeding dyad.

Conversely the child who seems to be failing to thrive for purely psychosocial reasons often has complicating organic issues. The undernourished child is lethargic and irritable, especially at feeding times. As noted above, undernutrition decreases LES tone and may worsen reflux: the undernourished child is more difficult to feed and holds down fewer calories. Poor nutrition adversely affects immunity: children with FTT often have recurrent infections that increase their caloric requirements and decrease their ability to meet them.

The mixed model reminds the clinician that FTT is an interactive process involving physiological and psychosocial elements and, more importantly, both parent and child. The child’s attributes affect the relationship as surely as the parents’. A fussy child may be more difficult for a particular parent to feed. A “good” or passive baby may not elicit enough feeding. Physical characteristics also affect parent-child relationships: organic disease may not only make feeding difficult but may engender a sense of failure or disappointment in the parent. It is crucial to remember that each child is different; parents have unique relationships with each of their children. Therefore, a parent whose first child is diagnosed with FTT is not doomed to repeat the cycle with the second child. Conversely, an experienced parent who has fed previous children successfully is not immune from the specter of FTT.

Causes of FTT

All failure to thrive is caused by undernutrition. The mechanism varies. The child may have increased caloric requirements because of organic disease. The child may have inadequate intake either because not enough food is made available or there is mechanical difficulty in eating.

Thirdly, adequate calories may be provided but the child is unable to utilize them either because the nutrients cannot be absorbed across the bowel wall or because of inborn errors of metabolism.

The astute clinician will note that there may be overlap between these mechanisms. For example, a child with cystic fibrosis has increased caloric requirements associated with chronic respiratory tract infections. However, shortness of breath may make it difficult for the child to eat sufficient quantities. And associated pancreatic insufficiency limits nutrient absorption.

FTT may be prevented by good communication between the primary care provider and the family. The practitioner should regularly assess feeding practices and growth and educate parents about appropriate age-specific diets. As a general rule, infants who are feeding successfully gain about

• 30 g/d at 0-3 months
  
• 20 g/d at 3-6 months
  
• 15 g/d at 6-9 months
  
• 12 g/d at 9-12 months
  
• 8 g/d at 1-3 years

In addition, growth parameters need to be recorded at every visit, sick or well. Weight should be documented for all children. Recumbent length is measured for children younger than 2 years old. Height is measured for children older than 3 years old. Between the ages of 2 and 3 years either height or length may be recorded. Length measurements exceed heights by an average of 1 cm. With a good growth chart in hand, the primary care provider can monitor growth and intervene early if problems arise.

Clinicians should investigate the economic stresses on families. In a family struggling with recent unemployment or underemployment, referral to a walk-in clinic or other social support programs may prevent hunger and subsequent FTT.

Symptoms and Signs

The importance of a complete, long-term growth curve in making the diagnosis of FTT cannot be overemphasized. Acute undernutrition manifests as “wasting”; the velocity of weight gain decreases while height velocity continues to be preserved. The result is a thin child of normal height. Chronic undernutrition manifests as “stunting”; both height and weight are affected. The child may appear proportionately small. Review of a growth curve may reveal that weight was initially affected and increase the suspicion for FTT.

Children should be plotted on an appropriate growth curve. Growth curves are gender specific and are available at the CDC Web site. Growth curves should not be used for specific countries of origin. Specific growth curves are available for children with genetic disorders such as Trisomy 21 or Turner syndrome. However, these curves are not well validated. These curves draw from a small group of children and the nutritional status of the participants was not assessed. These curves may be useful for the clinician in discussing an affected child’s growth potential with a family, but are not necessary. These growth curves must also be used with care.

History