Editor's note: This episode contains frequent and mildly graphic mentions of poop. It may cause giggles in children, and certain adults. When Dr. Andy Tagg was a toddler, he swallowed a Lego piece.

Sonia Grego works in a world of poop. Scatological-themed artwork hangs outside her office alongside peer-reviewed papers on human waste. “We have poop emojis everywhere,” she said, pointing to a ...