Differential Diagnosis for a 6-week-old Girl with Blood in Stool
- Single most likely diagnosis
- Allergic proctocolitis: This condition is a common cause of rectal bleeding in infants, especially those who are exclusively breastfed. The presence of blood and mucus in the stool, without other symptoms such as fever or vomiting, supports this diagnosis. The fact that the infant is well-appearing and has been gaining weight also points towards a benign condition like allergic proctocolitis.
- Other Likely diagnoses
- Anal fissure (despite none being found on examination, it's still possible for a fissure to be present and not visible): Anal fissures can cause bleeding in infants, especially if they are constipated or have hard stools. However, the absence of an anal fissure on rectal examination and the description of soft stools make this less likely.
- Infectious gastroenteritis: Although the patient has not had any fever, vomiting, or sick contacts, infectious gastroenteritis can still present with isolated rectal bleeding. The loose stools with blood and mucus could be indicative of an infection.
- Cow's milk protein allergy (in breastfed infants, this would be due to the mother consuming dairy products): This condition can cause rectal bleeding, diarrhea, and other gastrointestinal symptoms in infants. The fact that the patient is exclusively breastfed does not rule out this possibility, as the mother's diet can affect the breast milk.
- Do Not Miss
- Intussusception: Although this condition typically presents with intermittent abdominal pain, vomiting, and currant jelly stools, it can occasionally present with isolated rectal bleeding. Intussusception is a medical emergency that requires prompt diagnosis and treatment.
- Hirschsprung's disease: This congenital condition can cause rectal bleeding, diarrhea, and failure to thrive. Although the patient's weight is at the 25th percentile and has increased since the last checkup, Hirschsprung's disease is a condition that should not be missed due to its potential for serious complications.
- Volvulus or other intestinal obstruction: These conditions can cause rectal bleeding, abdominal pain, and vomiting. They are medical emergencies that require prompt diagnosis and treatment.
- Rare diagnoses
- Juvenile polyps: These are rare in infants and can cause rectal bleeding due to the presence of a polyp in the colon or rectum.
- Inflammatory bowel disease (IBD): Although extremely rare in infants, IBD can cause rectal bleeding, diarrhea, and abdominal pain.
- Congenital vascular malformations: These are rare conditions that can cause rectal bleeding due to abnormal blood vessels in the colon or rectum.