Failure to Thrive (FTT) / Faltering Growth

Introduction

Failure to Thrive (FTT), increasingly referred to as faltering growth or weight faltering in Canadian pediatric practice, is a common clinical scenario encountered in the MCCQE1. It represents a state of undernutrition where an infant or child fails to meet expected growth standards.

For the purpose of MCCQE1 preparation, it is crucial to understand the interplay between organic pathology and psychosocial factors (CanMEDS Health Advocate role), as well as the correct application of Canadian growth charts.

Definition and Diagnostic Criteria

FTT is a descriptive term, not a specific diagnosis. It describes a pattern of growth over time.

Growth Charts in Canada

The Canadian Paediatric Society (CPS) and Dietitians of Canada recommend:

• WHO Growth Charts: Used for all Canadian children aged 0–19 years (adopted in 2014 to replace CDC charts for this demographic).
• Correction for Prematurity: Use corrected age for infants born < 37 weeks gestation until 24–36 months of age.

Pathophysiology and Etiology

The core pathophysiology is an imbalance between caloric intake and metabolic requirements.

For MCCQE1, etiologies are classically categorized into three groups. However, inadequate caloric intake is the most common cause overall.

Clinical Approach

1. History (The High-Yield Component)

A detailed history reveals the etiology in the vast majority of cases.

• Dietary History: 24-hour recall (be specific about volumes, mixing ratios of formula, frequency).
• Past Medical History: Prematurity, meconium ileus (CF), recurrent infections.
• Family History: Stature of parents (calculate mid-parental height), constitutional delay, atopy, autoimmune diseases.
• Social History: Crucial for MCCQE1. Financial barriers, housing, substance use, supports.

2. Physical Examination

Focus on signs of malnutrition and underlying organic disease.

Investigations

Choosing Wisely Canada recommendation: Do not order a “shotgun” panel of investigations for FTT. Testing should be guided by history and physical exam.

Tier 1: Basic Screening (If history is inconclusive)

• CBC and differential (Anemia, infection)
• Ferritin (Iron deficiency)
• Urinalysis + Culture (Occult UTI, Renal tubular acidosis)
• Electrolytes, Creatinine, Urea (Renal function, hydration)

Tier 2: Targeted Testing (Based on clinical suspicion)

• Celiac Screen (TTG-IgA): If solids introduced, abdominal symptoms, or family history.
• Sweat Chloride: Gold standard for Cystic Fibrosis (if respiratory symptoms or steatorrhea present).
• Stool Studies: Ova & Parasites, fecal elastase.
• TSH: If growth velocity is slow (height affected early).

Management

Management is multidisciplinary. The goal is “Catch-up Growth” (typically 1.5 to 2 times the expected caloric intake for age).

Canadian Guidelines & Epidemiology

• Epidemiology: FTT affects 5-10% of children in primary care settings in North America.
• Indigenous Health: Be aware of higher rates of food insecurity in remote and Indigenous communities. Culturally safe care involves connecting families with community resources.
• Iron Deficiency: CPS recommends iron-rich foods as first solid foods (meat, iron-fortified cereals) at 6 months.

Key Points to Remember for MCCQE1

1. Most common cause: Inadequate caloric intake (Non-organic).
2. Terminology: “Weight faltering” is preferred over “Failure to Thrive”.
3. Growth Pattern: Weight drops first $\rightarrow$ Length drops second $\rightarrow$ Head Circumference drops last. If Head Circumference is small initially, think intrauterine or genetic/syndromic causes.
4. Re-feeding Syndrome: In severe malnutrition, rapid re-feeding can cause hypophosphatemia, hypokalemia, and hypomagnesemia. Monitor electrolytes.
5. Neglect: Is a form of maltreatment. Physicians have a legal duty to report suspected abuse/neglect to child protection services.

Sample Question

Scenario

A 9-month-old female is brought to the clinic by her mother due to concerns about “small size.” The infant was born at term. She was breastfed exclusively until 6 months, at which point pureed vegetables and fruits were introduced. The mother reports the infant is a “picky eater.”

On examination, the infant is alert and active.

• Weight: 6.5 kg (< 3rd percentile)
• Length: 68 cm (15th percentile)
• Head Circumference: 44 cm (50th percentile)

Her growth chart shows her weight was at the 50th percentile at birth, 25th at 4 months, and has now dropped below the 3rd. Physical examination is unremarkable. No dysmorphic features.

Which one of the following is the most appropriate initial step in management?

Options

• A. Order sweat chloride testing
• B. Admit to hospital for observation of feeding
• C. Obtain a detailed diet history and observe a feeding session
• D. Prescribe a proton pump inhibitor (PPI) for presumed GERD
• E. Refer immediately to a pediatric gastroenterologist

Explanation

The correct answer is:

• C. Obtain a detailed diet history and observe a feeding session

Explanation: This clinical vignette describes a classic presentation of faltering growth (FTT) characterized by a drop in weight percentiles with preserved length and head circumference (“wasting” rather than “stunting”). This pattern strongly suggests acute malnutrition due to inadequate caloric intake.

• Option C is correct: The vast majority (>80%) of FTT cases are due to inadequate caloric intake, often related to feeding behaviors, preparation errors, or inappropriate diet composition (e.g., low-calorie solids like plain vegetables without added fats). A detailed diet history (including a 3-day diet record) and directly observing the parent-child interaction during feeding are the highest yield and most cost-effective initial steps.
• Option A (Sweat chloride): This is for Cystic Fibrosis. While CF causes FTT, there are no respiratory symptoms or steatorrhea mentioned. This is a Tier 2 investigation.
• Option B (Admission): Hospitalization is reserved for severe malnutrition, medical instability, or failure of outpatient management. This child is alert and active.
• Option D (PPI): Empiric treatment for GERD is not indicated without symptoms of pathological reflux (vomiting, hematemesis, arching). “Silent reflux” is rarely a cause of isolated FTT.
• Option E (Referral): Specialist referral is indicated if primary care management (nutritional rehabilitation) fails or if a specific organic cause is identified.

References

1. Canadian Paediatric Society. (2020). Nutrition for Healthy Term Infants: Recommendations from Birth to Six Months.
2. Dietitians of Canada, Canadian Paediatric Society, College of Family Physicians of Canada, & Community Health Nurses of Canada. (2014). Promoting optimal monitoring of child growth in Canada: Using the new WHO growth charts.
3. Rourke, L., Leduc, D., & Rourke, J. (2020). Rourke Baby Record: Evidence-based infant/child health maintenance guide.
4. Kirkland, S. (2023). Failure to Thrive. In: Essentials of Pediatrics (Canadian Edition).
5. Choosing Wisely Canada. (2021). Paediatrics: Five Things Physicians and Patients Should Question.