Colitis, persistent diarrhea, and soy protein intolerance.

Four infants with suspected soy protein intolerance were studied prospectively. All had vomiting, diarrhea, hematochezia, and weight loss of more than 10%. Laboratory abnormalities included anemia (3), acidosis (3), hypoalbuminemia (3), hypernatremia (1), hyponatremia (3), and mild eosinophilia (2). Symptoms developed between three hours and five days after systematic testing with increasing volumes of soy formula. After challenge with soy protein formula, proctosigmoidoscopy and rectal biopsy were performed within 24 hours of developing stools with gross blood. Proctosigmoidoscopy showed both spontaneous and induced friability and loss of vascular pattern in mucosa. Rectal biopsy showed acute colitis with crypt abscesses, depletion of mucus from rectal glands, and polymorphonuclear leukocytes within the lamina propria. Soy protein-induced colitis should be suspected in those infants who present with persistent and bloody diarrhea after being fed soy formula.