present with bilious emesis, tenderness to palpation, irritability, and possibly bloody stools if there has been significant intestinal ischemia Hirschsprung enterocolitis may present a history of difficulty passing meconium and with similar symptoms due to a large bowel obstruction There may be an explosive release of stool on digital rectal exam In all these conditions, fluid requirements are significantly increased because of bowel wall edema Plain films including AP and left lateral decubitus views are indicated to evaluate for obstruction, and contrast studies (upper GI series for volvulus, contrast enema for intussusception, and Hirschsprung enterocolitis) may be required to make a definitive diagnosis if the patient is stable Pyloric stenosis causes severe vomiting in the young infant This is most often seen in male infants to weeks old An infant with pyloric stenosis may present to the ED afebrile, with significant dehydration and lethargy A careful history reveals that increasingly projectile, nonbilious vomiting is the predominant feature of the illness, and there may be a positive family history for pyloric stenosis The physical examination reveals the classic abdominal mass, or “olive,” in less than half of the cases Rarely, a peristaltic wave is noted to pass over the epigastric area Electrolytes typically show hypochloremia, hypokalemia, and alkalosis Ultrasound of the upper gastrointestinal tract confirms the diagnosis Necrotizing enterocolitis (NEC) most often occurs in premature infants in the first few weeks of life, but can also occur in term infants, usually within the first 10 days of life A history of an anoxic episode at birth or other neonatal stresses may precede NEC These infants are quite ill, with lethargy, irritability, anorexia, distended abdomen, and bloody stools Radiographs of the abdomen may show pneumatosis intestinalis caused by gas in the intestinal wall Neonatal appendicitis is another rare event, but several cases have been reported to closely mimic sepsis Rapid diagnosis is essential as mortality is high, and perforation worsens the prognosis The most common presenting signs are nonspecific and can also be seen with SBO and NEC, including irritability, vomiting, and abdominal distention There may also be hypothermia, ashen color, and shock as the condition progresses, as well as edema of the right abdominal wall and possible erythema of the skin in that area The WBC count may be elevated, with a left shift, and there may be a metabolic acidosis as well as DIC Ultrasound may be unreliable in this age, and abdominal radiographs may show a paucity of gas in the right lower quadrant, evidence of free peritoneal fluid, or a right abdominal wall thickened by edema Neurologic Diseases