The age of the infant is important. If the infant is <7 days old, swallowed maternal blood is a likely cause; in older infants, this is unlikely. Ask the mother about medications taken during pregnancy. Is the infant breast-feeding? Get a detailed description of the stool since type of stool and color of blood can all help to differentiate the bleeding source (see Section III above).
Physical examination
Evaluate the infant's peripheral perfusion. An infant with NEC can be poorly perfused and may appear to be in early or impending shock. Bruising may suggest a coagulopathy.
Examine naso-/oropharyngeal area for a source of bleeding.
Abdominal examination. Check for bowel sounds and tenderness. Hyperactive bowel sounds are more common in upper gastrointestinal bleeding. If the abdomen is soft and nontender and there is no erythema, a major intra-abdominal process is unlikely. If the abdomen is distended, rigid, or tender, an intra-abdominal pathologic process is likely. Abdominal distention is the most common sign of NEC. Abdominal distention may also suggest intussusception or midgut volvulus. If there are red streaks and erythema on the abdominal wall, suspect NEC with peritonitis. Malrotation with ischemic bowel can also present with peritonitis. If there is an abdominal mass, consider duplication. Consider Hirschsprung disease or malrotation if there is obstruction. Hepatomegaly, splenomegaly, or jaundice may indicate liver disease.
GU/anal examination. Does the infant have a rash? If the infant's condition is stable, perform a visual examination of the anus to check for anal fissure or tear. Look for polyps, masses, or fistulas. Gentle digital rectal examination with a lubricated pinky finger may reveal fissures or polyps. Bedside “anoscopy” can be done by placing a lubricated blood collection tube into the anus.
Laboratory studies
Initial studies
Fecal occult blood testing (FOBT). Hemoccult or other test for the presence of blood. This is not useful for screening for NEC. It is positive in more cow's milk–fed infants than formula-fed infants.
Apt test. To differentiate maternal from fetal blood if swallowed maternal blood is suspected. A positive test indicates that the blood is due to either gastrointestinal or pulmonary bleeding from the neonate. A negative test would indicate that the blood is of maternal origin.
CBC with differential. If a large amount of blood is lost acutely, it takes time for it to be evident on hemoglobin results; therefore, initial hemoglobin values may be unreliable. An increased white blood count suggests infection or thrombocytopenia (can be associated with NEC, sepsis).
Chemistry panel. High BUN can be seen in upper GI bleeding (resorption of blood in GI tract).
Coagulation studies. To rule out DIC or a bleeding disorder. The usual studies are partial thromboplastin time (PTT), prothrombin time (PT), fibrinogen level, and platelet count. Thrombocytopenia can also be seen with cow's milk–protein allergy. An elevated PT can indicate a coagulopathy. A prolonged PTT may indicate hemophilia.
Suspected NEC. If NEC is suspected, the following studies should be performed:
CBC with differential. To establish an inflammatory response and to check for thrombocytopenia and anemia.
Serum potassium levels. Hyperkalemia secondary to hemolysis may occur.
Serum sodium levels. Hyponatremia can be seen secondary to third spacing of fluids.
Blood gas levels. To rule out metabolic acidosis, which is often associated with sepsis or NEC.
Further studies
Stool studies. Certain pathogens cause bloody stools, but they are rare in the neonatal nursery. Obtain stool cultures for common pathogens, ova, and parasites. Stool smear for white blood cells (WBCs; elevated with colitis) and eosinophils (suggests allergic colitis).
Allergic enterocolitis diagnosis. Difficult because there is no specific laboratory test. Eosinophilia may be present in the serum and can be present in the stool. A rectal mucosal punch biopsy can show eosinophilic infiltration suggestive of an allergic origin.
Imaging and other studies
Immediate study
Abdominal radiograph. A plain radiograph of the abdomen is useful if NEC or a surgical abdomen is suspected. Look for an abnormal gas pattern, a thickened bowel wall, pneumatosis intestinalis, or perforation. Pneumatosis can appear as a “soap bubble” area (see Figure 11–23). If a suspicious area appears on the abdominal radiograph in the right upper quadrant, it is usually not stool. A left lateral decubitus view of the abdomen may show free air if perforation has occurred and it cannot be seen on a routine anteroposterior (AP) film. Surgical conditions usually show signs of intestinal obstruction. Most common sign in intussusception in premature infants is dilated bowel loops.
Additional studies
Abdominal ultrasound with color Doppler studies to diagnose intussusception. A pseudo kidney (longitudinal appearance of the intussuscepted segment of bowel) is seen with intussusception and Meckel diverticulum.
Contrast studies can be done for diagnosis of obstruction.
Endoscopy of upper gastrointestinal tract allows visualization of the esophagus, stomach, and duodenum and helps to identify the site of bleeding in the upper tract.
Electronic gastroscopy can be done in infants at 0–3 months. This can be used to assess upper gastrointestinal bleeding.
Meckel scan (technetium-99m pertechnetate nuclear scan) can help diagnose Meckel diverticulum.
Radioactive tagged red blood cell (RBC) scan can localize the site of lower GI bleeding if the source is unknown.
Colonoscopy can be done to rule out colitis, polyps, or other masses.
Rectal mucosal biopsy can show eosinophilia in the lamina propria in cases of allergic enterocolitis.
CT scan to evaluate for obstruction or see gastrointestinal hemangiomatosis.