Dr. Mark Fishbein at Central Dupage Hospital/Children's Memorial ###-###-####). He and his staff were great. Our then-infant son had serious gastroenterology problems for a short while around 7 months old caused by something called intussusception, for which he had to have emergency surgery at CDH, and we were given an appointment with Dr. Fishbein for his follow-up care. We only needed to go see him a couple of times since our son's issues pretty much resolved themselves. That was a year ago, so I don't know if Dr. Fishbein is still there, but you can't go wrong with any of the pediatric doctors at CDH/Children's.
My son was also seen by 2 other pediatric gastroenterologists: Dr. Esperanza Garcia-Alvarez at Lutheran General Hospital in Park Ridge, and Dr. Barbara Kirschner at University of Chicago, both of whom were highly recommended to us. They were both great as well, but they are not in the cities you requested. Dr. Garcia-Alvarez immediately diagnosed the fact that our son's diarrhea was probably the result of a particular strain of bacteria common in hospitals that he would have acquired during his hospitalization the previous week. She ordered a test to be done, which confirmed her probable diagnosis, so that he was able to be given medication to alleviate the problem. Dr. Kirschner was knowledgeable as well, but my son was pretty much fine by the time she saw him. She works with one of the top-rated pediatric gastroententerologists in the country - Dr. Stefano Guandalini, who I believe is head of the pediatric gastroenterology department at U of C.