The point of taking temperature is that you DON'T necessarily know what's happening.
Ileus (GI Stasis) is not a disease. It is a SYMPTOM of a problem. Stress, pain, discomfort all can trigger ileus. So treating the ileus alone will often not get to the root of the problem.
Ileus can result from fever. It also can result from hypothermia (which can be caused by shock, which can be caused by pain, etc.)
So taking temperature is an absolutely VITAL part of determing your bunny's state, and what to tell the vet. The most important thing is to learn to take temperature safely, which you can learn here.
Dana Krempels, PhD
Senior Lecturer
Department of Biology
University of Miami