When one has found 3 normal or hyperplastic glands and one is missing the upper parathyroid, look behind the oesophagus and pharynx. If the lower is missing open up the carotid sheath from the carotid bifurcation down to the upper mediastinum. If the fourth gland is still missing perform a cervical thymectomy on the side of the missing parathyroid. Cervical thymectomy is easy to do with virtually no complications. Identify the thymus at the lower pole of the thyroid .
Thymic tissue has unlike fat a distinct structure to it.
Separate the thymus from the thyroid and divide the thyro-thymic ligament, pick up the upper end of the thymus and pull the thymus by continual traction out of the chest. As the thymus is delivered a single vessel is see posteriorly and divided. Thymectomy should be virtually bloodless and often produces the missing gland. In parathyroid hyperplasia it is our policy to perform bilateral excision of both thymic lobes even though four glands have already been found. I f after all this dissection the fourth gland is still missing perform a total lobectomy of the thyroid on the relevant side in the hope that the missing gland is intra-thyroidal.