Differential Diagnosis for a 4-week-old Girl with Bright Red Blood in Stool
- Single most likely diagnosis:
- Allergic proctocolitis: This condition is a common cause of rectal bleeding in infants, especially those fed with cow's milk-based formula. The presence of bright red blood in the stool and the recent fussiness with feeds support this diagnosis.
- Other Likely diagnoses:
- Anal fissure: A possible cause of bright red blood in the stool, especially if the stool is hard or the infant is constipated. However, the looser-than-normal stool in this case makes it less likely.
- Infectious gastroenteritis: Although less common in breastfed infants, formula-fed infants like this patient can be affected. The presence of looser stool and blood could suggest an infection, but the lack of other symptoms such as fever or vomiting makes it less likely.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.):
- Intussusception: A life-threatening condition where a part of the intestine slides into another, causing bowel obstruction and potentially ischemia. Although it typically presents with currant jelly stool (a mixture of blood and mucus), any infant with rectal bleeding should be evaluated for this condition.
- Volvulus or intestinal malrotation: These are congenital anomalies that can cause intestinal obstruction and ischemia, presenting with bleeding, abdominal distension, and vomiting. Early diagnosis is crucial for survival.
- Hirschsprung's disease: A congenital condition characterized by the absence of ganglion cells in the distal bowel, leading to obstruction. It can present with enterocolitis, which may cause rectal bleeding.
- Rare diagnoses:
- Congenital vascular malformations: Abnormalities in blood vessels that can cause rectal bleeding, although these are rare and usually diagnosed prenatally or in early infancy.
- Inflammatory bowel disease (IBD): Conditions like Crohn's disease or ulcerative colitis are rare in infants and typically present with chronic diarrhea, weight loss, and abdominal pain, in addition to rectal bleeding.