enterocolitis, or pneumonia Obstruction may present with isolated vomiting A low-grade fever suggests an inflammatory process, including peritonitis A patient with episodic colicky pain with interposed quiet intervals, even in the absence of a “currant jelly” stool, should raise suspicion for intussusception or midgut volvulus An incarcerated hernia is a common cause of bowel obstruction in infants and young children Inguinal hernias may incidentally incarcerate during acute illnesses in young, crying infants and may be a cause of abdominal obstruction Signs of partial or complete obstruction with peritonitis indicate a perforated viscus from intussusception, volvulus, or, occasionally, appendicitis or Hirschsprung disease An upper GI radiographic series should be performed if malrotation is suspected Abdominal Pain Associated With Peritoneal Signs Rebound tenderness (including tenderness to percussion) or guarding suggests peritoneal inflammation Children with peritonitis will often avoid motion and keep their hips flexed to relieve tension on the abdominal musculature The abdomen may be distended, with decreased or absent bowel sounds In neonates and young infants, abdominal tenderness, which is associated with peritoneal findings or abdominal distention with or without emesis, should raise suspicion for necrotizing enterocolitis Systemic signs such as temperature instability, apnea, and lethargy may be present The presentation of a child with appendicitis may vary widely, and the clinical signs and symptoms depend upon the stage of disease Early in the course of illness children will most often complain of diffuse, nonspecific, periumbilical abdominal pain, nausea, and anorexia As disease progresses, vomiting, fever, and migration of pain to the right lower abdomen are common findings Ultrasound can be used to confirm the diagnosis of appendicitis, but the diagnosis cannot be excluded if the appendix is not well visualized, particularly early in the disease process CT imaging has excellent test characteristics in the diagnosis of appendicitis; however, the risk of radiation must be considered MRI has similar test characteristics to CT for the evaluation of appendicitis without the risk of radiation Various scoring systems, such as Alvarado Score and the Pediatric Appendicitis Score utilize historical factors, physical examination findings, and laboratory results such as peripheral white blood cell count to risk stratify patients for imaging or surgery (see Chapter 116 Abdominal Emergencies ) Peritonitis in a child with nephrotic syndrome or liver failure may be due to spontaneous bacterial peritonitis Pain localized to the epigastrium can be due to gastritis; however, the presence of peritonitis should raise suspicion for a perforated ulcer Cholecystitis and pancreatitis may also produce peritonitis, with