Areas of inflammation or ulceration are easily seen. Masses and strictures are also visible. In most cases, no. The endoscope has a tiny channel through which a biopsy instrument can be passed. Precise biopsies can be taken of areas of any of these organs that appear abnormal.
Many diseases cause changes that can only be detected by an inspection of the cells.
Even if the organ appears normal, biopsies are taken. In most cases, biopsy of the stomach of a vomiting cat or of the colon of a cat with diarrhea will be very helpful in determining the disease present. This depends on the size of the cat and the size of the endoscope. The vast majority of the small intestine is not accessible to endoscopy. Most diseases of the small intestine require other tests to be diagnosed.