What are the causes and treatment options for a baby presenting with hematochezia (blood in stool)?

Blood in Stool in Babies: Causes and Management

In infants presenting with hematochezia (blood in stool), the vast majority of cases are benign and self-limiting, with cow's milk protein allergy being the most common cause (53.3% of cases), followed by swallowed maternal blood, viral enteritis, and anal fissures. 1

Immediate Assessment Priority

Begin by assessing hemodynamic stability using the shock index (heart rate ÷ systolic blood pressure)—a value >1 indicates instability requiring immediate hospital referral and urgent intervention. 2

• Check vital signs including heart rate, blood pressure, capillary refill time, and mental status to identify signs of hypovolemia 2
• Obtain hemoglobin/hematocrit levels if available to assess bleeding severity 2
• Calculate shock index immediately—this single parameter determines whether the infant needs emergency care versus outpatient evaluation 2

Diagnostic Approach Based on Stability

For Hemodynamically Stable Infants:

Perform a digital rectal examination to identify anal fissures, hemorrhoids, or palpable masses as the first diagnostic step. 2

• Most infants with rectal bleeding (94%) are hemodynamically stable and can be managed outpatient, though 6% have underlying pathology requiring definitive diagnosis 2
• Obtain focused history including feeding type (breast vs. formula), onset timing, stool characteristics, and associated symptoms 2
• Consider the Apt test (alkali denaturation test) in newborns to distinguish maternal blood from infant blood—this is particularly important in the first days of life 3

For Hemodynamically Unstable Infants:

Immediate hospital transfer is mandatory with shock index >1, signs of hypovolemia, or hemodynamic instability. 2

• Transfuse packed red blood cells if hemoglobin <7 g/dL (target 7-9 g/dL) 2
• Perform CT angiography immediately to localize bleeding source before endoscopic intervention 2
• Always consider an upper GI source even with apparent hematochezia in unstable patients 2

Common Causes by Age and Clinical Context

Neonatal Period (First 28 Days):

Cow's milk protein allergy accounts for 53.3% of cases, making it the leading cause of bloody stools in neonates. 1

• Swallowed maternal blood syndrome occurs in 10% of cases—use Apt test for confirmation 1, 3
• Necrotizing enterocolitis (NEC) stage II or higher occurs in 8.3% of cases, more common in preterm infants and those who are bottle-fed 1
• Anal fissures account for 5% of cases 1
• Viral enteritis represents 9.7% of cases 1
• Median onset age for bloody stools is 12 days after birth 1

Critical distinction: Only 1.7% of neonates with bloody stools require surgery, with NEC being the most common surgical cause. 1

Beyond Neonatal Period (>28 Days to 2 Years):

Persistent symptoms beyond 1 month or recurrent bleeding requires colonoscopy to exclude polyps, inflammatory bowel disease, or structural lesions. 2

• Meckel's diverticulum should be considered if significant bleeding occurs without obvious source 2
• Colonoscopy after adequate bowel preparation is the preferred diagnostic test for persistent lower GI bleeding 2

Management Algorithm

Step 1: Hemodynamic Assessment

• Calculate shock index immediately
• If >1 or unstable → immediate hospital referral 2
• If ≤1 and stable → proceed to Step 2

Step 2: Physical Examination

• Digital rectal examination for fissures, hemorrhoids, masses 2
• If obvious benign cause identified (anal fissure) → conservative management
• If no clear source → proceed to Step 3

Step 3: Age-Specific Considerations

For newborns (0-7 days):

• Perform Apt test to rule out swallowed maternal blood 3
• If maternal blood confirmed → reassurance, no further workup needed
• If infant blood → obtain abdominal radiograph to evaluate for NEC 3, 4

For infants beyond newborn period:

• Trial of cow's milk protein elimination (maternal diet if breastfeeding, or hydrolyzed formula) 1
• If bleeding persists >1 month → colonoscopy referral 2

Step 4: Feeding Modifications

Exclusive breastfeeding is associated with lower rates of bloody stools and later onset age compared to formula feeding. 1

• For breastfed infants: maternal elimination of cow's milk protein for 2-4 weeks 1
• For formula-fed infants: switch to extensively hydrolyzed or amino acid-based formula 1
• Bottle-fed neonates with NEC have earlier onset of bloody stools compared to breastfed 1

Red Flags Requiring Urgent Evaluation

The following findings mandate immediate hospital assessment regardless of hemodynamic status:

• Shock index >1 2
• Signs of peritonitis (abdominal distension, tenderness, guarding) 5
• Bilious emesis suggesting obstruction 5
• Pneumatosis intestinalis on imaging suggesting NEC 6
• Coagulopathy (prolonged INR, PT, PTT) 6
• Severe electrolyte abnormalities (hypernatremia >150 mmol/L, metabolic acidosis) 6
• Preterm infants with any bloody stools (higher NEC risk) 1

Common Pitfalls to Avoid

Do not attribute bleeding to hemorrhoids or fissures without full evaluation in infants with persistent or recurrent bleeding—this may lead to missed diagnoses of inflammatory bowel disease or polyps. 7

• Do not delay Apt test in newborns—waiting for results while assuming benign cause can miss serious pathology like NEC 3, 4
• Do not assume stability will persist—approximately 6% of initially stable presentations have underlying pathology requiring intervention 2
• Do not perform nasogastric tube placement routinely, as it does not reliably aid diagnosis and can cause complications 7
• Do not continue cow's milk protein exposure without adequate trial of elimination (minimum 2-4 weeks) before declaring treatment failure 1

Prognosis and Follow-up

Bloody stools in neonates is generally a benign, self-limiting disorder with 100% survival rate and only 1.7% requiring surgical intervention. 1

• Most cases resolve with conservative management or dietary modification 1
• Preterm neonates have longer hospital stays and later onset of bloody stools compared to term infants 1
• Outpatient follow-up within 24-48 hours is appropriate for stable infants with benign causes 3
• Colonoscopy is indicated for persistent symptoms beyond 1 month or recurrent bleeding episodes 2