Can constipation cause a mild fever in a toddler? There are no other symptoms besides constipation and fever at 101-99

Not from my experia. I think most of my patients go thru a constipation phaze at one time or another, or it just seems so, but they don't generally run temp with it. The exception are some chronic retainers who in mid to late childhood skip the function for a week or so and end up so full & stressed that serial enemas are needed to clear them. I did have a 14 yo with 103 that resolved with enemas.
It shouldn't . Please have the child seen.