Some Crohn's cases might be easy, but finding granulomas isn't. Once the trouble area get sufficiently large so it can be seen during a colonoscopy, it's an easy decision. But those visible lesions don't always appear early.
Finding the odd granuloma in a blood test or tissue scraping is not easy. They just aren't that prevalent. It took the docs 8 years to find the granulomas that gave me the sarcoid diagnosis.
And if the granuloma was found in the blood stream, I wonder how they distinguished between Crohn's and Sarcoidosis?
"In her Advanced Placement high school science class, she was looking under the microscope at slides of her own intestinal tissue -- slides her pathologist had said were completely normal -- and spotted an area of inflamed tissue called a granuloma, a clear indication that she had Crohn's disease."
It was a bonehead doctor.