Differential Diagnosis for a 7-Month-Old Boy with Streaks of Blood in Stools
- Single Most Likely Diagnosis
- Anal Fissure: The presence of a small anal fissure at the 6 o'clock position, along with the introduction of new foods that can cause constipation (such as cow's milk-based formula and rice cereal), supports this diagnosis. The bright red blood on the outside of the stools is consistent with an anal fissure, which can cause pain and bleeding during defecation.
- Other Likely Diagnoses
- Constipation: The change in stool consistency to hard and pellet-like, occurring every 2-3 days, suggests constipation. This is a common issue in infants transitioning to solid foods or formula.
- Cow's Milk Protein Allergy or Intolerance: The introduction of cow's milk-based formula could be causing an allergic reaction or intolerance, leading to blood in the stool. However, the absence of other symptoms like vomiting, rash, or fever makes this less likely.
- Gastroenteritis: Although the patient has no fever or vomiting, a mild gastroenteritis could still cause blood in the stool. However, the lack of other symptoms and the specific pattern of stool changes make this less likely.
- Do Not Miss Diagnoses
- Intussusception: Although less common in this age group without a clear precipitant like a viral illness, intussusception is a life-threatening condition that requires immediate attention. The presence of blood in the stool and abdominal firmness could be indicative of this condition.
- Hirschsprung's Disease: This congenital condition affects the colon and can cause severe constipation and enterocolitis. The presence of constipation and blood in the stool, along with the absence of other clear causes, makes this a "do not miss" diagnosis.
- Rare Diagnoses
- Juvenile Polyps: These are rare in infants but can cause rectal bleeding. They are usually associated with a more significant amount of bleeding and might not fully explain the constipation.
- Inflammatory Bowel Disease (IBD): Although extremely rare in infants, IBD (including Crohn's disease and ulcerative colitis) can present with blood in the stool, diarrhea, and abdominal pain. The lack of systemic symptoms and the age of the patient make this diagnosis unlikely but not impossible.