In a postmortem examination, a veterinarian will open up the GI tract and look for lesions that are consistent with coccidia (see Figure 1 on page 23). Finally, the veterinarian will collect a sample of the intestine and look at the material under the microscope. A definitive diagnosis can be made from this examination.
It is important to remember that because coccidia is so prevalent, it is often found in the feces or intestines of chickens at necropsy. The significance of that finding is weighed against the visual and microscopic damage to the intestines.