Bloody Stool in Infants: A Differential Diagnosis Approach for Neonatal Hematochezia

Bloody stool in infants, or hematochezia, is a concerning symptom that can present in newborns and young babies. While alarming for parents, it’s crucial to understand that the causes range from benign and self-limiting to serious conditions requiring immediate medical or surgical intervention. For clinicians, establishing a prompt and accurate differential diagnosis is paramount to ensure appropriate management and optimal outcomes for these vulnerable patients. This article provides a comprehensive overview of the differential diagnosis of bloody stool in infants, drawing upon recent research and clinical insights to guide healthcare professionals in their assessment and management.

Understanding the Broad Spectrum of Causes

The appearance of blood in an infant’s stool can be due to a variety of underlying factors. These can broadly be categorized into benign, self-resolving conditions and those that signal significant pathology. Recognizing this spectrum is the first step in formulating a differential diagnosis.

Benign and Self-Limiting Causes

Several causes of bloody stool in infants fall into the benign category, often resolving without specific intervention. These include:

• Swallowed Maternal Blood: This is a common cause in the first few days of life. Blood can be swallowed during delivery or from breastfeeding if the mother has cracked nipples. The infant is otherwise well, and the blood is digested, resulting in dark or black stools, but sometimes fresh red blood can also be seen.
• Anal Fissure: Small tears in the anal mucosa, often caused by constipation or hard stools, can lead to streaks of bright red blood on the stool or diaper. Infants may be fussy or cry during defecation.
• Cow’s Milk Protein Allergy (CMPA): This is a prevalent allergy in infancy. Exposure to cow’s milk protein, either through formula or breast milk (if the mother consumes dairy), can cause allergic colitis. Bloody stools are a common symptom, often accompanied by other signs like vomiting, diarrhea, eczema, and fussiness.

Serious and Potentially Life-Threatening Conditions

While many cases are benign, bloody stool can also be a sign of serious conditions that demand prompt diagnosis and treatment. These include:

• Necrotizing Enterocolitis (NEC): This is a severe intestinal disease, primarily affecting preterm infants, but also seen in term infants. NEC involves inflammation and necrosis of the intestinal wall and is a surgical emergency. Bloody stools are a key symptom, often preceded by feeding intolerance, abdominal distension, and lethargy.
• Infectious Enteritis: Viral or bacterial infections can cause inflammation of the intestines, leading to bloody stools. Common culprits include rotavirus, norovirus, Salmonella, Shigella, and Campylobacter. Other symptoms include fever, vomiting, and diarrhea.
• Intestinal Malrotation with Volvulus: This is a surgical emergency where the intestine twists on itself, cutting off blood supply. Bloody stools are a late sign, preceded by bilious vomiting, abdominal distension, and pain.
• Hirschsprung’s Disease: This congenital condition involves missing nerve cells in the colon, leading to bowel obstruction. While typically presenting with constipation and abdominal distension, bloody stools can occur due to enterocolitis.
• Coagulation Disorders: Rarely, bleeding disorders can manifest as bloody stools in infants. This might be due to vitamin K deficiency, hemophilia, or disseminated intravascular coagulation (DIC).
• Sepsis: Systemic infection can affect the gastrointestinal tract and lead to bloody stools, particularly in neonates.

Age of Onset: A Key Diagnostic Clue

The age at which bloody stools first appear can provide valuable clues in narrowing down the differential diagnosis.

• Early Onset (within the first few days of life): Swallowed maternal blood is the most likely cause in this period. Intestinal malrotation with volvulus, although rare, should also be considered as it can present very early.
• Onset within the First Week or Two: Anal fissures can occur in the first weeks. NEC typically presents within the first few weeks, especially in preterm infants. Viral enteritis can also manifest in this age group.
• Later Onset (after the first week or two): CMPA is a more common cause of bloody stools presenting after the first week of life, often around 2-8 weeks. Infectious enteritis, particularly bacterial, can occur at any age, but is more common as infants get older and are exposed to a wider range of pathogens.

Feeding Method and its Relation to Bloody Stool

Feeding choice plays a significant role in the differential diagnosis of bloody stool in infants.

• Exclusively Breastfed Infants: While breast milk is generally protective, CMPA can still occur in exclusively breastfed infants if the mother consumes cow’s milk products. Swallowed maternal blood from nipple fissures is also relevant in this group.
• Formula-Fed Infants: Formula feeding, particularly with cow’s milk-based formulas, is a major risk factor for CMPA. NEC is also more commonly seen in formula-fed preterm infants compared to exclusively breastfed preterm infants.

Delving Deeper into Specific Conditions

To further refine the differential diagnosis, it’s essential to understand the specific characteristics and diagnostic approaches for the most common causes of bloody stool in infants.

Cow’s Milk Protein Allergy (CMPA)

CMPA is a leading cause of bloody stool in infants, especially those presenting after the first week of life.

• Clinical Presentation: Besides bloody stools (allergic colitis), infants with CMPA may exhibit vomiting, diarrhea, excessive crying, eczema, and poor weight gain. Symptoms often develop gradually after the introduction of cow’s milk protein.
• Diagnosis: Diagnosis is primarily clinical, based on history and symptom improvement upon elimination of cow’s milk protein from the infant’s diet (or the mother’s diet if breastfeeding). Oral food challenges can be used to confirm the diagnosis but are not always necessary. Stool tests for occult blood or inflammatory markers (like fecal calprotectin) may support the diagnosis.

Necrotizing Enterocolitis (NEC)

NEC is a critical differential diagnosis, particularly in preterm infants, due to its severity and need for urgent intervention.

• Clinical Presentation: NEC typically presents with feeding intolerance, abdominal distension, vomiting (often bilious), lethargy, temperature instability, and bloody stools. Symptoms can progress rapidly.
• Diagnosis: Diagnosis is based on clinical findings combined with radiographic evidence of pneumatosis intestinalis (air in the bowel wall) on abdominal X-ray. Blood tests may show signs of infection and metabolic disturbances. Bell’s staging criteria are used to classify NEC severity.

Swallowed Blood Syndrome

This benign condition needs to be differentiated from true gastrointestinal bleeding.

• Clinical Presentation: Infants with swallowed blood syndrome are typically well-appearing, with no other symptoms. The bloody stools may be dark or bright red, and the onset is usually in the first few days of life.
• Diagnosis: A key diagnostic test is the Apt-Downey test, which can differentiate fetal hemoglobin (from swallowed maternal blood) from adult hemoglobin (indicating infant bleeding). Careful history taking regarding maternal nipple trauma or delivery events is crucial.

Viral Enteritis

Infectious causes must be considered, especially in older infants and those in daycare settings.

• Clinical Presentation: Viral enteritis typically presents with watery diarrhea, vomiting, fever, and abdominal cramps. Bloody stools, if present, are usually less prominent than in CMPA or NEC.
• Diagnosis: Diagnosis is often clinical, based on symptoms and epidemiological factors (outbreaks, daycare exposure). Stool viral PCR testing can identify specific viral pathogens if needed, but is not routinely performed in mild cases.

Anal Fissure

This is a common, benign cause of rectal bleeding in infants.

• Clinical Presentation: Anal fissures present with streaks of bright red blood on the stool surface or diaper. Infants may be fussy during defecation, and examination may reveal a visible fissure in the anal verge.
• Diagnosis: Diagnosis is usually clinical, based on the characteristic presentation and physical examination.

Figure 1: Causes of Bloody Stool in Infants: A Comparison Between Preterm and Term Infants, highlighting the prevalence of Cow’s Milk Protein Allergy (CMPA) and Necrotizing Enterocolitis (NEC).

Diagnostic Approach: A Step-by-Step Guide

When faced with an infant presenting with bloody stools, a systematic diagnostic approach is crucial:

1. History and Physical Examination:

   • Detailed History: Age of onset, feeding history (breast milk, formula type), stool characteristics (color, consistency, frequency), associated symptoms (vomiting, fever, abdominal distension, rash), maternal health history, and delivery history.
   • Thorough Physical Exam: General appearance, vital signs, abdominal examination (distension, tenderness, bowel sounds), perianal examination (anal fissures), and assessment for dehydration.

2. Initial Investigations:

   • Stool Studies: Fecal occult blood test (if not overtly bloody), stool culture (if infectious enteritis suspected), stool for viral PCR (if viral enteritis suspected, especially in outbreaks), and fecal calprotectin (may be elevated in CMPA and inflammatory bowel disease, though less specific in neonates). Apt-Downey test if swallowed maternal blood is suspected.
   • Blood Tests: Complete blood count (CBC), electrolytes, blood glucose, coagulation studies (PT/INR, PTT) if bleeding disorder suspected, C-reactive protein (CRP) or procalcitonin (PCT) if sepsis or NEC suspected.

3. Imaging Studies:

   • Abdominal X-ray: Essential in suspected NEC or intestinal obstruction. Look for pneumatosis intestinalis, dilated loops of bowel, or free air.
   • Abdominal Ultrasound: May be helpful to rule out pyloric stenosis (if vomiting is prominent), or to assess for free fluid or other abdominal pathology.
   • Contrast Enema: May be considered in older infants if Hirschsprung’s disease is suspected, but not typically the first-line investigation for bloody stools in neonates.

4. Specialized Investigations (if indicated):

   • Endoscopy/Colonoscopy: Rarely needed in neonates with bloody stools, but may be considered in older infants with persistent or unexplained rectal bleeding to visualize the mucosa and obtain biopsies.
   • Allergy Testing: If CMPA is suspected and dietary elimination is not diagnostic, allergy testing (skin prick test or serum IgE for cow’s milk protein) may be considered, although these tests have limitations in infants with non-IgE mediated CMPA (allergic colitis).

Management and Treatment Strategies

Management of bloody stool in infants is guided by the underlying diagnosis.

• Swallowed Maternal Blood and Anal Fissures: These are usually self-limiting and require no specific treatment other than reassurance and addressing constipation if present in cases of anal fissure (e.g., with dietary fiber or stool softeners in older infants).
• CMPA: Management involves eliminating cow’s milk protein from the infant’s diet. For formula-fed infants, switch to extensively hydrolyzed or amino acid-based formulas. For breastfed infants, maternal dairy elimination is necessary.
• NEC: Requires urgent medical and often surgical management. This includes NPO (nothing per os), intravenous fluids, antibiotics, respiratory support, and surgery if bowel perforation or severe disease is present.
• Infectious Enteritis: Management is primarily supportive with oral or intravenous rehydration. Antibiotics are generally not indicated for viral enteritis. Bacterial enteritis may require antibiotics depending on the pathogen and severity.
• Intestinal Malrotation with Volvulus and Hirschsprung’s Disease: These conditions require surgical intervention.
• Coagulation Disorders and Sepsis: Require specific medical management directed at the underlying condition.

Figure 2: Age of Onset of Bloody Stool in Infants as a Diagnostic Indicator: Differentiating Causes Based on Onset within or after the First 7 Days of Life, including CMPA and NEC.

Conclusion

Bloody stool in infants presents a diagnostic challenge requiring a systematic and thoughtful approach. While many cases are benign, it is crucial to promptly identify and manage serious underlying conditions like NEC and intestinal obstruction. Understanding the differential diagnosis based on age of onset, feeding history, associated symptoms, and appropriate investigations allows clinicians to provide timely and effective care, ensuring the best possible outcomes for these young patients. A strong emphasis on breastfeeding support and judicious use of antibiotics are important considerations in the overall management strategy.

References

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