What are the possible causes and management options for a breastfed 2-month-old infant presenting with hematochezia (blood in stool)?

Blood in Stool of Breastfed 2-Month-Old Infant

In a breastfed 2-month-old infant with blood in the stool, the most likely diagnosis is cow's milk protein allergy (CMPA), which accounts for 53.3% of cases and should be managed with a 2-4 week maternal elimination diet removing at least milk and eggs from the mother's diet. 1, 2

Most Common Causes in Order of Frequency

The differential diagnosis for hematochezia in this age group includes:

• Cow's milk protein allergy (53.3%) - most common cause overall 2
• Swallowed maternal blood (10.0%) - from cracked nipples during breastfeeding 2, 3, 4
• Viral enteritis (9.7%) - often with virus particles visible on colonic epithelium 1, 2
• Necrotizing enterocolitis (8.3%) - more common in preterm infants 2
• Non-specific enteritis (7.3%) 2
• Anal fissure (5.0%) 2

Initial Diagnostic Approach

First, perform the Apt-Downey test (alkali denaturation test) to differentiate swallowed maternal blood from infant blood - this is the single most important initial test to avoid unnecessary workup. 3, 4

Key Clinical Features to Assess

• Feeding pattern: Document if exclusively breastfed (68% of cases are fully breastfed) 1
• Stool characteristics: Bloody stools typically occur irregularly, averaging 2.1 episodes per day for a mean of 6 days 1
• Presence of atopic eczema: Found in 38% of cases and associated with persistent CMPA at 1 year 1
• Growth parameters: Normal growth argues against serious pathology 1
• Clinical stability: Most infants (87.5% in one series) can be managed outpatient 1

Warning Signs Requiring Urgent Evaluation

Look for signs indicating surgical conditions or serious pathology:

• Bilious vomiting 5
• Abdominal distension or tenderness 5
• Fever or lethargy 5
• Hemodynamic instability 5
• Prematurity (higher NEC risk) 2

Management Algorithm

Step 1: Rule Out Swallowed Maternal Blood

• Perform Apt-Downey test immediately - if positive for maternal hemoglobin, reassure and discharge 3, 4
• Examine maternal nipples for cracks or bleeding 4

Step 2: If Infant Blood Confirmed, Initiate CMPA Trial

Implement a strict 2-4 week maternal elimination diet removing at least cow's milk and eggs - this is the evidence-based first-line treatment. 5, 1

• Small amounts of cow milk protein ingested by mother are expressed in breast milk and can trigger symptoms 5
• Continue exclusive breastfeeding during elimination diet 5
• Do NOT empirically stop breastfeeding - breastfeeding should continue whenever possible 5

Step 3: Monitor Response

• Bloody stools typically resolve within mean of 24 days (range 1-85 days) from presentation 1
• If symptoms persist beyond 1 month on elimination diet, proceed to further workup 1

Step 4: Additional Testing if No Response to Elimination Diet

Order the following if bleeding persists after 2-4 weeks of maternal elimination diet:

• Stool culture for Salmonella, Shigella, Yersinia, Campylobacter, and C. difficile 1
• Fecal viral studies for rotavirus, adenovirus, and enterovirus 1
• Consider colonoscopy if bleeding persists - typically shows focal mucosal erythema and aphthous ulcerations 1

Step 5: Formal CMPA Diagnosis

Perform cow's milk challenge at appropriate time to confirm diagnosis - this is essential to avoid false-positive diagnoses and unnecessary prolonged dietary restrictions. 1

Important Caveats

A cow's milk elimination diet does NOT affect the duration of rectal bleeding in the short term - bleeding resolves over the same timeframe regardless of dietary intervention, but the diet prevents recurrence. 1

Only 18% of infants with rectal bleeding actually have confirmed CMPA - the majority remain idiopathic, making challenge testing critical to avoid overdiagnosis. 1

Surgical intervention is extremely rare (1.7% of cases) - this is a generally benign, self-limiting condition. 2

Exclusive breastfeeding is protective - only 28% of infants with bloody stools were exclusively breastfed, suggesting formula feeding increases risk. 2

Prognosis

• 100% survival rate in recent case series 2
• Most infants are symptom-free by 1 year of age 1
• At 1 year follow-up, approximately 18% still have confirmed CMPA, with some developing multiple food allergies 1
• Presence of atopic eczema and histopathologic colonic inflammation at presentation predict persistent CMPA at 1 year 1