Apparatus and methods are described for use with feces of a subject that are disposed within a toilet bowl, and an output device. One or more light sensors are configured to receive light from the toilet bowl, while the feces are disposed within the toilet bowl. A computer processor analyzes the received light, and, in response thereto, detects a currently-occurring inflammatory bowel disease episode, and/or a predicted upcoming inflammatory bowel disease episode. The computer processor generates an output on the output device, at least partially in response thereto. Other applications are also described.