Thanks for choosing health care magic for posting your query.
I have gone through your question in detail and I can understand what you are going through.HCG
diet may not be the cause for this kind of pain. Yes it can be due to kidneys and ureters. Many times a ureteric calculi may cause such pains and for that you need to get a USG scan of the abdomen.You may also get a routine urine examination which may show up RBCs if it was indeed a ureteric calculi.
Hope I am able to answer your concerns.
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Wish you good health,
Dr. Srikanth Reddy M.D.