How can one diseased parathyroid gland be found?

Find parathyroid. 1. Ultrasound because it's cheap and can be done by most high volume practitioners in their office. 2. 4D CT. This is new but far superior to the former number 2. 3. SPECT CT Tc 99 sestamibi or other sestamibi based scan. 4. If you go to 4 or beyond, your a special case and make sure you have a really experienced surgeon.
Ultrasound. An abnormal parathyroid gland may be detected by ultrasound examination of the neck or by a nuclear scan of the neck (sestamibi). If the abnormal gland is only slightly enlarged both tests may be negative. In that case an experienced surgeon is the solution to finding the gland at surgery.
Blood work and scan. The first step in diagnosis is blood work. Overactive parathyroid glands cause high levels of blood calcium. This can be found on routine blood work and patients often have no symptoms initially. A number of things can cause parathyroid problems, but if a parathyroid "adenoma" is the cause, parathyroid scanning will determine which of the 4 parathyroid glands in the neck are involved.
Several options. In my order of preference: parathyroid sestamibi scan, neck ultrasound, surgical exploration with gamma probe for radio guidance, ct scan of the neck, MRI of neck.