What is the approach to evaluating a case of failure to thrive?

Diagnostic Approach to Failure to Thrive

A comprehensive, systematic evaluation is essential for diagnosing and managing failure to thrive (FTT), focusing first on identifying common causes before pursuing extensive testing. The approach should prioritize careful growth assessment, detailed history, targeted physical examination, and selective laboratory testing based on clinical findings.

Definition and Initial Assessment

• FTT is characterized by inadequate weight gain relative to established norms, typically defined as weight below the 3rd-5th percentile for age and sex, weight less than 80% of ideal weight for height, or deceleration in growth crossing two major percentile lines on standardized growth charts 1
• Document weight, height, and head circumference on standardized growth charts at each visit to establish growth trajectory and identify concerning patterns early 1
• Distinguish true FTT from normal growth pattern variations, as approximately 25% of normal infants will shift to a lower growth percentile in the first two years of life and then follow that percentile consistently 2

Comprehensive History

• Prenatal and birth history: Assess for polyhydramnios, intrauterine growth restriction, prematurity, and birth weight/length as these can affect early growth patterns 1
• Feeding history: Document feeding difficulties, including:
  • Breastfeeding or formula preparation practices
  • Volume and frequency of feeds
  • Swallowing difficulties
  • Vomiting or reflux symptoms
  • Introduction and tolerance of solid foods 1, 3
• Family history: Identify genetic conditions, growth disorders, or metabolic diseases that may contribute to poor growth 1
• Social history: Evaluate family dynamics, caregiver mental health, economic resources, and potential for neglect or abuse 4

Physical Examination

• General appearance: Look for dysmorphic features suggesting genetic syndromes 1
• Growth parameters: Plot weight, height, and head circumference and calculate weight-for-height ratio 1
• Nutritional status assessment: Evaluate for:
  • Muscle wasting
  • Decreased subcutaneous fat
  • Hair, skin, and nail changes suggesting nutritional deficiencies 5
• Systemic examination: Focus on signs of underlying organic disease:
  • Cardiac murmurs or abnormal heart sounds
  • Respiratory distress or abnormal breath sounds
  • Abdominal distension, organomegaly, or tenderness
  • Neurological abnormalities affecting feeding 1, 3

Laboratory and Diagnostic Testing

• Initial laboratory evaluation should be targeted based on history and physical examination findings, not performed as a routine battery of tests 6
• First-line laboratory tests when clinically indicated:
  • Complete blood count to assess for anemia, infection, or hematologic disorders 1
  • Comprehensive metabolic panel to evaluate electrolytes, renal function, and acid-base status 1
  • Thyroid function tests to rule out hypothyroidism 1
  • Urinalysis to assess for renal tubular disorders 1
• Additional testing should be guided by specific clinical findings:
  • Swallowing studies for suspected dysphagia 1
  • Endoscopy for persistent gastrointestinal symptoms 1
  • Genetic testing for suspected chromosomal abnormalities 1

Differential Diagnosis

• Inadequate caloric intake (most common cause):
  • Improper formula preparation
  • Feeding difficulties
  • Oral-motor dysfunction
  • Behavioral issues
  • Neglect 3, 4
• Increased caloric requirements:
  • Hyperthyroidism
  • Chronic infections
  • Malignancy
  • Cardiopulmonary disease 3
• Defective utilization:
  • Malabsorption syndromes
  • Metabolic disorders
  • Inflammatory bowel disease
  • Celiac disease 3
• Genetic disorders:
  • Chromosomal abnormalities
  • Inborn errors of metabolism 1

Management Approach

• All children with FTT need additional calories for catch-up growth (typically 150% of the caloric requirement for their expected weight, not actual weight) 2
• Nutritional interventions:
  • Increase caloric density of feeds
  • Optimize feeding schedule and techniques
  • Consider supplemental formulas or tube feeding for severe cases 3
• Treat underlying medical conditions when identified 3
• Hospitalization criteria:
  • Severe malnutrition
  • Failed outpatient management
  • Suspected abuse or neglect
  • Need for close monitoring of feeding interactions 2, 4
• Monitor for refeeding syndrome in severely malnourished children by increasing food intake slowly and supplementing phosphate, magnesium, and potassium 3

Follow-up and Monitoring

• Regular follow-up visits to monitor growth response to interventions 1
• Adjust nutritional plan based on growth trajectory 1
• Consider multidisciplinary approach involving:
  • Nutritionist/dietitian
  • Occupational or speech therapist for feeding issues
  • Social services for family support
  • Subspecialty referrals based on identified medical conditions 1, 6
• Notify child protective services when evaluation leads to suspicion of abuse or neglect 4

Special Considerations

• Children with Down syndrome, intrauterine growth restriction, or prematurity follow different growth patterns than typical infants and should be plotted on appropriate growth charts 2
• Psychosocial factors often coexist with medical conditions in FTT cases, requiring attention to both aspects for successful management 4