The most common cause of failure to thrive is poor nutrition combined with environmental factors. The diagnosis can generally be made based on the physical examination, review of the growth curves, and parental heights. However, there are medical causes of growth deficiency that should be considered. In most cases, a thorough history and physical can screen for these causes.
The following tests are recommended for an initial laboratory evaluation of failure to thrive:
CBC and differential - chronic bleeding, iron deficiency anemia, lead toxicity, malignancy, and infection
Urinalysis, urine culture - kidney or bladder infection or renal disease
Serum electrolytes - renal tubular acidosis and other causes of acidosis
T4, TSH - hyperthyroidism, hypothyroidism
PPD - tuberculosis screening
Other serum chemistries, such as serum albumin, calcium, phosphorus, liver function tests - malnutrition, rickets, liver disease
Erythrocyte sedimentation rate - chronic illness
Stool tests - guaiac, culture, fat, ova, and parasites
HIV testing - dependent on risk, newborn screen results, and historical information
If any of the above tests are abnormal, hospital admission and further testing may be necessary. Hospital admission is often useful in assisting in the diagnosis of nutritional failure to thrive. A baby who gains weight with adequate nutrition as documented in the hospital does not generally have an underlying medical or organic reason for poor weight gain.
In all cases of failure to thrive, review the New York State Newborn Screening Program test results. In addition, many experts recommend a chest radiograph to look for occult findings, such as rib fractures. A skeletal survey also may be indicated. For more information about radiograph recommendations, see
RADIOLOGY: Skeletal Survey.
