volvulus and signifies vascular compromise NEC, most common in preterm infants (although 10% occur in term infants), signifies sections of bowel tissue necrosis The diagnosis of Hirschsprung disease should be considered in any newborn who does not pass meconium in the first 24 to 48 hours of life Twenty-five percent of neonates with Hirschsprung disease have enterocolitis that may present with GI bleeding The risk of enterocolitis remains high until about months of age Infancy (1 Month to Years) In the first years of life, anal fissures and colitis (including infectious and allergic) are among the most common causes of rectal bleeding Anal fissures are usually associated with constipation or trauma (rarely, this trauma can be nonaccidental) Infectious enterocolitis as a cause of bloody diarrhea is common in all age groups Pseudomembranous colitis should be considered in any infant or child with bloody stools and a history of recent antibiotic therapy “Nonspecific colitis” is a common cause of hematochezia in infants younger than months of age and may represent a variation in the colonic response to viral invasion Milk- or soy-allergic enterocolitis causes bloody diarrhea and usually occurs during the first month of life, but can occur in older children depending on food exposure Trialing a change in formula from cow’s milk or soy protein to an elemental formula (Nutramigen, Alimentum, Pregestimil) can also help to assess for milk protein allergy Breast-fed infants whose mothers drink cow’s milk may develop an allergic colitis that responds to removal of cow’s milk from the mother’s diet Food protein–induced enterocolitis syndrome (FPIES) represents a rare (affects up to 0.34% of infants) but severe, non–IgE-mediated food hypersensitivity that causes severe vomiting and diarrhea (often bloody) within hours of offending food ingestion Symptoms, including hypovolemic shock, typically begin in the first month of life, with a mean age at initial presentation of 5.5 months Infants typically react to one or two specific foods with the most common being soy and cow’s milk, and, less commonly, rice, vegetables, fruits, meats, oats, egg, and fish Most children develop tolerance to the offending food trigger by years of age Meckel diverticulum should be suspected in infants or young children who present with intermittent painless rectal bleeding (dark or red blood) that may cause massive GI hemorrhage Sixty percent of complications from Meckel diverticulum (hemorrhage and intestinal obstruction) occur in patients younger than years of age Idiopathic intussusception may occur in infancy, with 80% occurring before years of age Lymphonodular hyperplasia is an uncommon cause of rectal bleeding in this age group and may cause mild, painless hematochezia that is self-limited Intestinal duplications are also an uncommon cause of lower GI bleeding and, when diagnosed, are usually found in children younger than years of age Duplications can be found anywhere in the GI tract but are most common in the distal ileum and usually present with obstruction and lower GI bleeding