No single theory (or therapy) has gained uniform acceptance Colic may be a syndrome that represents the manifestations of some or all these factors in varying degrees in a population of babies whose tendency to cry varies along a normal distribution Multiple studies have documented crying in early infancy They show that crying tends to cluster in the evening, and daily crying times increase from birth to a peak of approximately hours per day at to weeks, followed by a rapid decline Although there are variations in the literature, most agree that a reasonable definition for colic embraces Wessel criteria: an infant younger than months of age with more than hours of crying per day occurring more than times per week for more than weeks EVALUATION AND DECISION A careful history, physical examination, and rarely, additional studies, should enable the physician to diagnose identifiable illnesses or injuries causing severe paroxysms of crying ( Table 20.1 ) The history should elicit the onset of crying and any associated events— particularly trauma, fever, use of medications, or recent immunization (irritability lasting up to 24 hours has been described after pertussis vaccination, however this is less common with DTaP than historically reported after DTP) Because feeding is vigorous exercise for the young infant, irritability with feeds may indicate ischemic heart disease Alternatively, yeast infections of the mouth, or severe reflux, may cause infants to cry with feeding Parents may recall a pattern of crying after maternal ingestion of specific foods in infants who are breastfeeding Irritability on being picked up (“paradoxic irritability”) may indicate a fractured bone or meningeal inflammation Crying with manipulation of an arm may indicate a clavicle fracture sustained during birth Physical examination must be thorough, with the infant completely undressed Vital signs may reveal either low or high temperature—suggesting infection (see Chapter 31 Fever ), or hyperpnea—suggesting metabolic acidosis (see Chapter 95 Metabolic Emergencies ) or increased intracranial pressure The head should be explored for evidence of trauma and the fontanel should be palpated Eyes must be examined with fluorescein to look for corneal abrasion, even in infants with no symptoms referable to the eyes In addition, eversion of the upper eyelids can exclude a foreign body Fundoscopy should be attempted because retinal hemorrhages are common signs of abuse, especially in abusive head trauma Careful otoscopy is required to visualize the tympanic membranes The heart should be evaluated for signs of congestive failure or arrhythmia ( Table 20.1, I.C ) Abdominal examination must be performed to detect signs of peritonitis