It is convenient to organize the many diverse causes of regurgitation and vomiting into age-related categories ( Table 81.1 ) Although there is considerable overlap, the most common and serious entities can be easily organized into such groupings EVALUATION AND DECISION General Approach Given the myriad causes of vomiting, an orderly approach to the differential diagnosis of this symptom is critical Three clinical features should guide initial evaluation and management: the child’s age , evidence of obstruction , and signs or symptoms of extra-abdominal disease Other important considerations include appearance of the vomitus, overall degree of illness (including the presence and severity of dehydration or electrolyte imbalance), and associated GI symptoms History The history should focus on the key elements noted above The patient’s age is often significant because certain critical entities (especially those that cause intestinal obstruction) are seen predominantly in neonates and older infants, and are less common in children beyond the first year of life Evidence of obstruction, including abdominal pain, obstipation, nausea, distention, and increasing abdominal girth, is sought in addition to vomiting Associated GI symptoms may include diarrhea and anorexia The suspicion of significant extra-abdominal organ system disease is raised by neurologic symptoms such as severe headache, stiff neck, blurred vision or diplopia, clumsiness, personality or school performance change, or persistent lethargy or irritability; by genitourinary symptoms such as flank pain, dysuria, urgency and frequency, hematuria, or amenorrhea; by infectious complaints such as fever, sore throat, or rash; or by respiratory complaints such as cough, increased work of breathing, or chest pain ( Tables 81.2 , 81.3 , and 81.4 ) Other associated GI symptoms may include diarrhea, anorexia, flatulence, and frequent eructation with reflux The appearance of the vomitus (by history and inspection when a specimen is available) is often helpful in establishing the site of pathology Undigested food or milk should suggest reflux from the esophagus or stomach caused by lesions such as esophageal atresia (in the neonate), gastroesophageal reflux (GER), or pyloric stenosis Bilious vomitus suggests obstruction distal to the ampulla of Vater, although it may occasionally be seen with forceful prolonged vomiting of any cause when the pylorus is relaxed Fecal material in the vomitus is seen with