Thanks for the additional information,
Well the first things to do here would be to get a colonoscopy, mnay disease can be missed on a CT scan which would show up on a colonoscopy. The presence of chronic constipation, abdominal pain and loss of appetite suggests that you get this doen to rule out a few possiblities such as, Colon CA, it is unlikely that you get it at this young age but the possiblity exists and also to rule out inflammatory bowel disease which sometimes only presents with constipation which is unusual presentation.
It can also pick up on any other abnormality of the GI tract whgich has been missed on other tests.
Secondly, if you havent, you should undergo GI motility studies which will indicate if the stomach is emptying properly or not, sometimes the stomach emptying time is delayed and as a result these symptoms can occur. This is called Gastroparesis which can be a consequence of Diabetes, autonomic neuropathies etc.
Lastly instead of labelling you as a oatient with depression, the possiblity of Irritable Bowel Syndrome should also be considered its pretty common for irritable bowel syndrome to present as only constipation. It can bhe treated with many drugs including tegaserod.
Also its worthwhile ruling out metabolic and endocrine problems such as Diabetes mellitus, Addisons disease
....addisons is a disease in which the adrenals are damaged...its function can be checked by doing a serum cortisol level at different times of bthe day. this is a possiblity vthat can be looked at. Also the possiblity of abdomina;l tuberculosis can be there, that if you have travelled to a country where this is prevalent or been in contact with people with tuberculosis.
I hope i have provided you with some new possiblities if not please let me know
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