A mother brings a boy, 1 year old, to the Emergency Department with a 5 month history of diarrhea which is described as frequent liquid stools. There is no blood in the stool. The child has not been vomiting and has abdominal pain. Weight gain slowed significantly after about 6 months of age. There are no known sick contacts. The child is fully immunized and is formula fed plus a variety of solids. Family history reveals that the child's father has hypothyroidism. On examination the child looks pale. The vital signs are as follows, bp: normal, hr: normal and temp: 36.6°C. Abdomen is mildly distended. Perianal examination is normal. Skin examination is normal.