What Could Cause High Blood Urea Levels and How Can it Be Lowered?

I have a 7 yr. old nephew. Last year doctors found his blood urea was high. They did all series of tests but didn't find any cause. I'd like to get your opinion on that. What do you think can cause this or what kind of tests are useful?

I should first mention that I am a licensed acupuncturist and herbalist, so my scope of practice and expertise is not in western medicine. Therefore, not only am I not legally allowed to make a diagnosis according to western medicine, but that is also not the main way that I determine what is wrong with my patients. Granted, I can use information taken from western exams and diagnoses to also guide what I look for and what I do in my treatments, but that information is generally quite secondary to what I employ in my work as a practitioner of acupuncture and Oriental medicine (AOM). In AOM, we do a very detailed interview (of the patient or, when the patient is too young, we get information from the patient's relatives) and also look at the patient's tongue, pulses, skin, eyes, etc. We base our AOM diagnosis on symptoms (the subjective information about what the patient or patient's relatives tell us) and signs (the objective information we get from observing and examining the patient). This AOM diagnosis is important for us since our treatments with acupuncture and herbs are determined and understood on the basis of this traditional (rather than western medicine) diagnosis. Since I have not done a detailed interview and exam of your nephew and since I don't know anything about him except this one sign, it would be very difficult for me to try to make a determination about what is wrong, even according to AOM.
With that said, I did some investigation on what possible causes may be associated with high blood urea, according to western medicine. The list included possible kidney damage or kidney illness (including diabetes-caused nephropathy) hemolysis (excessive breakage of red blood cells), hypothyroidism, steroid usage, or temporary dehydration. Furthermore, these increased blood urea levels can indicate any condition that reduces the kidneys' ability to filter body fluids in the body or that interferes with protein breakdown. I don't know what sort of specialists in western medicine your nephew has been examined by, but it would seem, based on the above possible causes, that perhaps you might have him see a nephrologist, hematologist and/or endocrinologist. Without knowing how high his levels were, I don't know how far out of range his blood urea was. Also, I am assuming that you had the tests done more than one time and at different labs, in order to rule out the possibility of some errors in the test results. If that is not the case, then I would suggest you do that.
Lastly, if you're interested in pursuing treatment for your nephew with a practitioner of AOM, I would suggest you bring him to someone local to you who can examine your nephew in person. For more information on where or how to find qualified practitioners in your area, I would suggest you check out my reply on this website to a previous question on Richter's Chinese medicine Q & A, "Who Can I Turn To For Expert Information on Herbs?" This reply has some information and links in it about where to look on the internet for referrals to qualified AOM practitioners. You can look for practitioners who just do acupuncture or ones who do both acupuncture and herbs. I wish you much luck with your efforts to help your nephew.