Differential Diagnosis for a 12-month-old Female with a Bloody Diaper

Single Most Likely Diagnosis

• Anal Fissure: This is a common cause of rectal bleeding in infants, often resulting from the passage of a hard stool. The pain associated with an anal fissure can cause the infant to become constipated, creating a cycle of hard stools and further irritation.

Other Likely Diagnoses

• Gastroenteritis: Infections that cause diarrhea can lead to bloody stools, especially if the diarrhea is severe and causes rectal irritation.
• Food Allergy or Intolerance: Allergies to foods like cow's milk can cause gastrointestinal symptoms, including bloody stools.
• Intussusception: Although more common in older infants, intussusception (where a part of the intestine slides into another part) can cause bloody stools and is a significant concern.

Do Not Miss Diagnoses

• Intestinal Intussusception: As mentioned, this condition requires immediate medical attention because it can lead to bowel ischemia and necrosis if not treated promptly.
• Meckel's Diverticulum: A congenital anomaly of the small intestine that can cause painless rectal bleeding due to the presence of ectopic gastric mucosa.
• Hirschsprung's Disease: A condition characterized by the absence of ganglion cells in the distal bowel, leading to severe constipation and potentially enterocolitis, which can cause bloody stools.

Rare Diagnoses

• Juvenile Polyps: Benign growths in the colon that can cause rectal bleeding.
• Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease and ulcerative colitis are rare in infants but can cause chronic diarrhea, abdominal pain, and bloody stools.
• Vascular Malformations: Rare congenital conditions that can cause bleeding from the gastrointestinal tract.

Best Plan Moving Forward

1. History and Physical Examination: A thorough history to identify any recent changes in diet, stool pattern, or signs of infection, along with a physical examination to look for signs of distress, abdominal tenderness, or palpable masses.
2. Stool Tests: To check for infections (e.g., gastroenteritis) and blood.
3. Imaging Studies: Depending on the suspicion of conditions like intussusception or other structural abnormalities, an abdominal ultrasound or other imaging may be necessary.
4. Consultation with a Specialist: If the diagnosis is unclear or if there are concerns about conditions requiring specialized care (e.g., surgical conditions like intussusception or Meckel's diverticulum), consultation with a pediatric gastroenterologist or surgeon may be necessary.

Given the single episode of bloody diarrhea without additional symptoms, initial management may include monitoring for further episodes, dietary adjustments, and possibly a rectal examination or stool tests. However, any signs of distress, persistent bleeding, or other concerning symptoms should prompt immediate medical evaluation.