1. Medical School, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
2. Hospital de Clínicas de Porto Alegre, Pediatric Gastroenterology Unit, Porto Alegre, RS, Brazil
3. Department of Pathology, Hospital de Clínicas de Porto Alegre, Pathology Unit, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
4. Department of Pediatrics, Hospital de Clínicas de Porto Alegre, Pediatric Gastroenterology Unit, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil