The assessment of the acutely crying infant in the emergency department (ED) is challenging, and the clinician must resist the urge to rush through the history and physical examination. The clinician must be deliberate in the search for the cause, since the clues to the diagnosis may be subtle. The clinician should perform serial observations and examinations until the cause is found or the infant returns to normal behavior. Fortunately, with a thorough history, a meticulous physical examination, limited diagnostic tests, and a period of observation in the ED, most of the diagnoses of the crying, irritable infant are identified.¹

To unravel the cause of acute, unexplained crying, it is important to know what normal infant crying encompasses and the definition of colic. Crying is part of normal psychomotor and psychosocial development and is the infant’s source of communication. The infant cry may signal hunger, an unmet need for attention, need for a diaper change, or distress or pain.

The normal crying pattern in the first year of life has been described.² There is a progressive increase in crying, which peaks in the second month of life and then gradually decreases.^2,3 The peak crying time may be as much as 2 to 3 hours per day at 6 weeks of life.⁴ The daily crying time decreases when the infant has other ways to communicate, such as interacting with a social smile. Infant crying time has been reported to usually decrease to 1 hour a day by 14 weeks of age (3.5 months).³

Colic is a chronic crying syndrome that occurs in the first 3 months of life. The etiology of colic is unknown. Colic typically begins at 3 weeks of age in an otherwise healthy infant. The infant with colic cries more than 3 hours per day, more than 3 days per week, and at least 3 weeks in duration (the rule of 3s).⁵ During a colic episode, infants flex their legs, their faces turn red, and they expel flatus. These episodes usually take place in the early evening hours.⁵ Colic usually resolves by 3 to 4 months of age. Colic is a diagnosis of exclusion arrived at after careful history, physical examination, and workup as outlined below.⁶ It should be kept in mind that persistent crying in an infant is a risk factor for child abuse.

The cornerstone of colic treatment is reassuring the parents that this is a common, benign self-limited condition. Simethicone drops are widely used but there is little evidence to support their efficacy.⁷ There is little evidence to support any particular treatment of colic.^7,8 Dietary changes (protein hydrolysate formula, soy formula, and maternal hypoallergenic diet in breastfeeding mothers)⁹ have been recommended as well as swaddling, vibration, and massage.^7,10,11 Phenobarbital, dicyclomine (Bentyl), and ethanol should not be used because of the potential for significant adverse effects.¹⁰ There is some evidence to support the use of sucrose.¹²

Crying may also be a symptom of an underlying medical problem. The parents usually bring the infant to the ED because of the intensity and/or the duration of the crying and concern that their infant may be in pain. The clinician must differentiate between the benign and serious causes of crying. It is critical not to miss the serious causes because these may lead to untoward morbidity or death. In the seriously ill-appearing infant the assessment will occur in the critical care area of the ED with the history, physical examination, and diagnostic interventions occurring concurrently. This chapter focuses upon the well-appearing crying infant. Although the differential diagnosis is broad, an organized conservative approach with a thorough history and examination will narrow the differential in the majority of cases.^1,13,14

As Sir William Osler reminds us, “Listen to the patient, he is telling you the diagnosis.”¹⁵

Listen attentively to the history from the parents, since the clues to the diagnosis often lie in the history.¹ What elements should the history include? Crying should be investigated as a symptom. Questions should be directed to diagnose the symptoms: When did it start? What time of day? How long? What seems to provoke the crying? Was there any trauma? What alleviates the crying? What is the quality of the cry, high-pitched or weak? Are there any related symptoms such as fever, vomiting, diarrhea, constipation, cough, and/or nasal congestion? Has there been any exposure to illness? What is the duration of the crying? Is there a recurrent pattern?