Colic - etiology and epidemiology

Colic often is diagnosed using Wessel’s rule of threes—crying for more than 3 hours per day, at least 3 days per week, for more than 3 weeks. The limitations of this definition include the lack of specificity of the word crying (e.g., does this include fussing?) and the necessity to wait 3 weeks to make a diagnosis in an infant who has excessive crying. Colicky crying is often described as paroxysmal and may be characterized by facial grimacing, leg flexion, and passing flatus.
Etiology: Fewer than 5% of infants evaluated for excessive crying have an organic etiology. Because the etiology of colic is unknown, this syndrome may represent the extreme of the normal phenomenon of infant crying. Nonetheless evaluation of infants with excessive crying is warranted.
Epidemiology: Cumulative incidence rates of colic vary from 5% to 19% in different studies. Girls and boys are affected equally. Studies vary by how colic is defined and by data collection methodology, such as maintaining a cry diary or actual recording of infant vocalizations. Concern about infant crying also varies by culture, and this may influence what is recorded as crying or fussing. The clinician who evaluates a crying infant must differentiate serious disease from colic, which has no identifiable etiology. The history includes a description of the crying, including duration, frequency, intensity, and modifiability. Associated symptoms, such as leg flexion, facial grimacing, vomiting, or back arching, should be identified. Other important historical clues include the onset, diurnal pattern, any changes in quality, and triggers or activities that relieve crying. A review of systems can identify or eliminate other serious illnesses. Medical history also is important because infants with perinatal problems are at increased risk for neurologic causes of crying.
Attention to the feeding history can reveal feeding-related problems, including hunger, air swallowing (worsened by crying), gastroesophageal reflux, and food intolerance. Questions concerning the family’s ability to handle the stress of the infant’s crying and their knowledge of infant soothing strategies assist the clinician in assessing risk for parental mental health comorbidities and developing an intervention plan suitable for the family. The diagnosis of colic is made only when the physical examination reveals no organic cause for the infant’s excessive crying. The examination begins with vital signs, weight, length, and head circumference, looking for effects of systemic illness on growth. A thorough inspection of the infant is important to identify possible sources of pain, including skin lesions, corneal abrasions, hair tourniquets, skeletal infections, or signs of child abuse such as fractures. Infants with common conditions such as otitis media, urinary tract infections, mouth ulcerations, and insect bites may present with crying. A neurologic examination may reveal previously undiagnosed neurologic conditions, such as perinatal brain injuries, as the cause of irritability and crying. Observation of the infant during a crying episode is invaluable to assess the infant’s potential for calming and the parents’ skills in soothing the infant. Laboratory and imaging studies are reserved for infants in whom there are history or physical examination findings suggesting
an organic cause for excessive crying.
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