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Based on the CT report and your symptoms it is most likely to be Inflammatory Bowel Disease (IBD) but can never say precisely since a colonoscopy and biopsy would be the gold standard to confirm diagnosis in such a case. That is why it has been scheduled as the next step. Your doctor's wanted to go from non-invasive to invasive tests that is why they did the CT abdomen first and this is the protocol.
The soft tissue lesion in the right iliac fossa can be a previously inflammed appendix, appendicular mass, benign tumors like carcinoids (which would present with diarrhoea, anxiety, palpitations, flushing of the face etc), and possibly a malignant growth of either the cecum or the appendix, but that can only be ruled out on a colonoscopy with biopsy of the lesion.
Certain factors like history of malignancy in the family, genetic, dietry and life style can all lead to assumptions and educated guesses, but like I mentioned before it would be required that a formal colonoscopy be done and a biopsy obtained and sent to the lab for histopathology.
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