Links To The Cribsiders’ “#39: Failure To Thrive”

In this post, I link to The Cribsiders#39: Failure to Thrive – Growing into Focused Management. NOVEMBER 24, 2021.

All that follows is from the above resource.


Dr. Adolfo Molina (Pediatric Hospitalist at UAB) joins The Curbsiders for a deep dive on all things Failure to Thrive! From the 3 broad buckets of the FTT differential, the red flags to keep an eye on, and how a lab-heavy hospital workup is almost never needed!

Failure to Thrive Pearls

  1. The very best diagnostic tool in getting to the underlying cause of Failure to Thrive is the history and physical!
  2. The differential for FTT can be broken up into the same broad reasons anyone loses weight
    1. Not enough in
    2. Too much out
    3. Burning up too much
  3. Weight → Height → Head Circumference is the order in which things should drop off. If not in that order, that is a red flag for underlying issues besides nutrition.
  4. Kcal/kg/day is the most helpful metric to rely on when determining how much intake is enough. Generally speaking, in the first few months of life, infants should be gaining 30g/day and taking in 100kcal/kg/day.
  5. Recommended indications for admission include dehydration/intractable vomiting, symptomatic hyponatremia from under-mixing, or a concern for a specific disease process requiring expedited, in-patient work-up.

Failure to Thrive Show Notes 

Overview of Failure to Thrive (FTT)

Expert opinion: There is no one universally accepted definition of FTT. Dr. Molina simply defines FTT as a “young child recently out of the neonate phase that is having trouble growing” (Jaffe 2011). He relies most on weight/time (age) as a metric. Weight/age that is crossing two z-scores is a good indicator of malnutrition. Weight for length and mid-upper arm circumference is advocated for by the North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition (NASPGHAN) and the American Society for Parenteral and Enteral Nutrition (ASPEN) as good metrics, however, these measurements can often be unreliable if the measurer and/or data interpreter are untrained (Becker 2015Beer 2015).

It is important to remember though that growth charts are a bell curve and that someone has to be at the bottom statistically. Some kids may be low on the percentiles and just ride that percentile their whole life and it is not a problem. That is why time is such a key factor to put into gauging a child’s growth.

Is there an age limit to FTT?

More often than not, it’s talking about infants (<1 y of age). When patients are older, malnutrition is used more. However, an infant who is “failure to thrive” is also considered mild, moderate, or severely malnourished, as “Failure to thrive” is not technically a diagnosis (nor is it a diagnostic code that can be billed for).

Growth Charts

When evaluating a growth chart we should always be evaluating if the growth is symmetric or asymmetric. Our bodies are made to preferentially feed calories to the brain. Therefore, if the head circumference is not being spared in malnutrition that is a red flag for an underlying disease process. Examples of such include an underlying syndrome, metabolic disorder, TORCH infection, antenatal ischemic insult/stroke, or neuroanatomic abnormality.  Additionally, if height is preserved, this makes an underlying endocrinological problem much less likely (Bennett 2014Mei 2004).

Weight → Height → Head Circumference is the order in which things should drop off!

*For more information on growth charts, please see:

When to send to ED/Admit?

There’s no clear answer for this, but it is clear that the majority of FTT care can be done in the ambulatory setting. Especially as many studies have shown that a large laboratory/imaging workup for FTT is not needed most of the time (Khan 2021). The important question to ask is “what can we do during a hospitalization to really help?” The most common indications for admission  are

  • Dehydration/intractable vomiting
  • Symptomatic hyponatremia from under-mixing
  • Concern for a specific disease process requiring expedited work-up

The “Buckets” of FTT

The differential for FTT can be broken up into the same broad reasons anyone loses weight (Schwartz 2000):

  • Not enough in (too few calories)
  • Too much out (not absorbing calories)
  • Burning up too much (using too many calories)

Not Enough In

  • The feeding history is arguably the most important aspect of evaluating a patient with FTT. It is important to quantify as much as you are able how many calories are getting into the infant each day on average. Start from a non-judgmental place and always be cognizant of cultural differences in how caretakers choose to feed their child. Also, take into account social determinants of health surrounding the patient: does this caretaker have access to WIC, is there food insecurity, etc.
    • How many scoops of formula to water? Do you put water in first or the powder first? How many bottles do you prepare in a day? How many ounces per bottle? Who mixes bottles?
  • How do we know how much is enough?
    • Every infant is different. But in a general sense, in the first couple of months of life, 2-4 oz every 3-4 hours is sufficient.
  • A reliable metric is calories/kg/day, the gold standard is approximately 90-100kcal/kg/day for the first 6 months of life.
  • Weight/length can often be unreliable as length of an infant is a hard measurement to physically take.
  • Expert opinion: If a FTT work-up is done inpatient, as long as the pt has proven that they can take in the goal amount of calories each without frank vomiting or vital signs issues, they do not need to show weight gain. The day to day weight of an infant is so reflective on voiding and stooling that it is hard to get an accurate gauge.

If it’s not “not enough in,” what’s the lab work-up?

  • Trick question! Labs are really not super helpful. There is no “work-up” for FTT.  (Sills 1978Khan 2021)
  • Remember red flag symptoms that may be concerning!
  • Cardiac disease
    • Sweating during feeds
    • Hepatomegaly
    • Cyanosis
  • Neurologic
    • Loss of milestones
    • Poor tone
    • Poor suck
  • Abdominal/Malabsorption
    • Diaper dermatitis
    • Profuse vomiting

Complications of FTT

  • Most concerning would be the effects of severe malnutrition such as Marasmus or Kwashiorkor which are the extremes. Most of the time, these patients are caught before they develop. Signs of both are listed below.
    • Marasmus (low calories and protein): low weight for height, low height for age, large head relative to body, emaciated arms/thighs/buttocks with loose folds due to loss of subcutaneous fat, irritable behavior, thin and dry skin, thin/sparse hair that is easily plucked
    • Kwashiorkor (low protein): weight for age variable, low height for age, moon face, edematous extremities, apathetic behavior, distended abdomen with dilated loops of bowel, hepatomegaly, thin/dry and peeling skin with areas of hyperkeratosis and hyperpigmentation (dermatosis), dry/dull hair that can be hypopigmented
    • (Graphic 111603, UpToDate)
  • It is important to keep in mind that FTT often has a basis in the physiology as well as in the social determinants of health of the child. The long-term effects of FTT haven’t been explicitly studied, but it is reasonable to conclude that the neurodevelopment of a child is greatly impacted at least in the acute phase.


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