projectile Emesis tends to worsen in frequency and severity over days to weeks In the past, diagnosis was made by clinical history and palpation of the hypertrophied pyloric muscle, or “olive” in the abdomen Infants often presented with dehydration and electrolyte abnormalities caused by repeated vomiting, typically a hypokalemic, hypochloremic metabolic alkalosis However, with earlier presentation and diagnosis, fewer patients have an olive palpated at diagnosis, and the majority not have the classic electrolyte derangements at presentation HPS is associated with erythromycin use in the first two weeks of life; however, no association has been found between macrolide use during pregnancy or breastfeeding and HPS HPS should be suspected in the young infant presenting with progressively worsening nonbilious emesis, and can be diagnosed using ultrasound A hypertrophied pylorus with muscle wall thickness of mm or greater and length of 15 mm or greater with no passage of gastric contents into the small intestine confirms the diagnosis Treatment is surgical, with laparoscopic pyloromyotomy Prior to surgery, the patient should be well hydrated and any electrolyte abnormalities should be corrected Intussusception occurs when one portion of the bowel telescopes into its distal segment, commonly the terminal ileum into the cecum The peak incidence for intussusception is between months and years of age, although it remains one of the most common causes of obstruction up to years of age Patients typically present with intermittent episodes of abdominal pain, during which they may cry or pull up the legs Children may be lethargic between episodes, and infants may present only with lethargy and without the classic episodes of pain Bilious emesis and blood-tinged “currant jelly” stools may be seen However, the classic triad of abdominal pain, vomiting, and bloody stools is seen in less than a quarter of children with intussusception, so a high level of clinical suspicion must be maintained when any of these symptoms are present (refer Chapter 53 Pain: Abdomen ) Less common causes of obstruction should also be considered in infants presenting to the ED with vomiting A thorough clinical examination should be performed to evaluate for signs of incarcerated inguinal or umbilical hernias Meckel diverticulum, which results from incomplete obliteration of the omphalomesenteric duct, is the most common congenital anomaly of the GI tract in children While the majority of patients are asymptomatic, children can occasionally present with obstruction Enteric duplication cysts can also lead to intestinal obstruction or can act as lead points for intussusception While the clinician must first rule out obstructive causes of vomiting in infants, nonobstructive causes are more common than obstructive causes Nonobstructive causes of vomiting in this age group include GI, infectious, neurologic, renal, and metabolic disorders GER is a common cause of emesis in this age group GER results when relaxation of the LES allows retrograde passage of gastric contents Infants with GER may present with repeated episodes of emesis of stomach contents usually within 30 minutes of feeding Emesis is generally nonbloody and nonbilious, and is fairly constant over time Most infants will have some degree of GER or “spitting up,” with a peak at age months (up to 67% of infants) and gradually tapering over the first year of life GER that causes troublesome symptoms for the patient is referred to as gastroesophageal reflux disease (GERD) Troublesome symptoms that suggest GERD include poor weight gain, vomiting associated with irritability or refusal to feed, arching of the back during feeding, and respiratory symptoms such as cough or wheezing related to reflux For infants who present with reflux but without any of these troublesome symptoms, there is generally no need for any further diagnostic testing or for medical management Nonpharmacologic treatments suffice for the vast majority of infants with reflux Upper GI contrast radiography and esophageal pH probes are the most commonly used tests in the diagnosis and evaluation of GERD, but are almost never indicated in the PED for reflux evaluation Management of both GER and GERD should include lifestyle modifications These modifications can include feeding changes such as avoiding overfeeding, thickening feeds, and continuation of breastfeeding As milk–protein allergy can mimic GERD, a trial of eliminating milk and eggs from the diet of mothers of breast-fed infants or a trial of hydrolyzed protein formula in formula-fed infants may be warranted Medications should be reserved for infants with continued worrisome symptoms of GERD after trials of feeding modifications, with the two classes of medications most commonly used in infants being histamine-2 receptor antagonists (H2RAs) and proton pump inhibitors (PPIs) Medications should be given a 2- to 4-week trial, with weaning if symptoms improve It is important to stress to parents that these medications will reduce acid exposure in children with GERD, but that they will not decrease the amount of reflux itself There has been a shift away from acid-suppression therapy because of lack of efficacy and possible adverse effects Viral gastroenteritis is another common cause of vomiting in infants The infant will generally present with diarrhea as well, although they may present without diarrhea or early in the disease course before diarrhea has developed It is crucial to assess hydration of infants presenting with gastroenteritis and to ensure adequate oral intake, particularly in those infants who also have diarrhea as this age group is at much higher risk of dehydration than older children Vomiting in infants may also be caused by pathology of organ systems outside the digestive system and should be considered in the infant presenting with vomiting These include infectious, neurologic, renal, and metabolic causes Infections outside the GI tract can present with vomiting in infants One of the most common infections to cause vomiting outside of the GI tract is UTI UTIs are a common source of fever in children, particularly in infants Clinical symptoms are often nonspecific in infants, but may include vomiting in as many as one-third of infants with UTI, poor feeding, or malodorous urine Infants with pneumonia may also present with fever and vomiting, along with tachypnea, cough, or increased work of breathing Any respiratory illness causing cough, including bronchiolitis, pneumonia, and pertussis, can be associated with posttussive emesis in this age group Neurologic causes of vomiting in infants include CNS infections such as meningitis, hydrocephalus, intracranial mass, and intracranial hemorrhage Signs and symptoms of increased ICP in infants may include vomiting in addition to lethargy, irritability, bulging anterior fontanel, seizures, or focal neurologic findings Other causes of vomiting outside the GI tract include renal and metabolic causes Infants with renal tubular acidosis (RTA) may present with vomiting, growth failure, and recurrent episodes of dehydration Children with renal failure may also present with vomiting Vomiting can be an early symptom of many of the inborn errors of metabolism, including urea cycle disorders and organic acidemias Infants with inborn errors of metabolism may present with vomiting, lethargy, and poor feeding, and this diagnosis should be kept in the differential diagnosis of infants presenting with recurrent vomiting Older Child In the older child, several of the obstructive causes of vomiting can continue to occur, although less commonly than in infancy Children in this age group may present with malrotation and volvulus, intussusception, incarcerated hernia, or enteric duplication cysts Children with a history of abdominal surgery may present with bowel obstruction caused by adhesions Signs of obstruction in this age group include vomiting (particularly bilious), abdominal distention, and pain Nonobstructive causes of vomiting continue to be more common than obstructive causes of vomiting in older children GI causes such as appendicitis, peptic ulcer disease, and gastroenteritis can lead to vomiting, as well as several extra-abdominal causes Appendicitis can present with vomiting in children, along with other symptoms including abdominal pain, anorexia, and fever Often, pain will begin in the periumbilical region and then shift to the right lower quadrant, and pain may be increased with coughing or hopping (Chapters 53 Pain: Abdomen and 116 Abdominal Emergencies ) Other nonobstructive causes of vomiting in older children related to the digestive system include pancreatitis, cholelithiasis and cholecystitis, gastritis, and peptic ulcer disease Children with pancreatitis may present with vomiting and severe pain and tenderness in the epigastric region Children with cholelithiasis may present with vomiting and pain in the right upper quadrant, with symptoms worsening particularly after eating fatty foods, while those with cholecystitis may present with similar symptoms with the addition of fever Peptic ulcer disease may also present with vomiting, as well as abdominal pain worst in the epigastric region and hematemesis in severe cases Acute gastroenteritis (AGE) is the most common cause of vomiting in this age group AGE is an infection characterized by diarrhea, often accompanied by vomiting and is a common reason for children to present to the ED Fever may or may not be present The degree of dehydration will help to determine how to manage the child Several scales exist to assess the severity of dehydration (mild, moderate, or severe) in children with AGE based on physical examination, including criteria from the World Health Organization (WHO), the Gorelick scale, and the Clinical Dehydration Scale (CDS) These scales may have limited utility in some settings, and percentage loss of weight, although not often readily available in the ED, is the gold standard for assessing degree of dehydration Laboratory studies may also be helpful in children with signs of severe dehydration, with serum bicarbonate level having been shown to correlate with dehydration in several studies, but are rarely indicated in children with mild or moderate dehydration (see Chapter 22 Dehydration ) Intravenous fluids are generally recommended for the treatment of severe dehydration, and admission to the hospital may be indicated in these children, particularly if ongoing losses exceed intake However, oral rehydration should be attempted prior to intravenous rehydration in children with mild or moderate dehydration Ondansetron may be helpful in children prior to attempting oral rehydration in vomiting patients It is important that parents realize that rehydration in the ED is only the first phase of treatment of dehydration, with the second and third phases being replacement of ongoing losses and continuation of normal feeding Education on how to replace ongoing fluid losses after discharge from the ED should be provided Symptoms will generally improve over a few days to a week