The anatomy of primary hyperparathyroidism.

Although several classic anatomic studies describing the number, location, size, and weight of normal parathyroid glands have been reported, as detailed description of the parathyroid glands in a large series of patients with primary hyperparathyroidism has not been available. Drawings were made of the exact locations of each of the normal and enlarged parathyroid glands identified, immediately following neck explorations in all patients with primary hyperparathyroidism during a 4-year period (1977 to 1981). The enlarged glands were also measured and weighed after excision. The records of 273 patients were reviewed. Single gland enlargement (adenoma) was found in 218 patients (80%). Hyperplasia of all identified parathyroid glands was found in 42 patients (15%). Two adenomas (at least two other glands grossly and microscopically normal) were found in seven patients (2.6%). Seven patients (2.6%) with biochemical evidence of the disease had only normal glands at neck exploration. Adenomas in ectopic locations were frequent. However, their locations, with few exceptions, were predictable. The larger an adenoma, the more likely it was to be ectopic. Right superior gland adenomas (mean size 2.6 cm) were ectopic in 39%. Left superior glands (mean size 2.62 cm) were ectopic in 36%. No superior parathyroid adenomas were intrathyroidal. five of 223 (2%) adenomas were entirely surrounded by thyroid parenchyma in the lower pole. Nearly all inferior gland adenomas within the thymus could be readily excised through the cervical incision. In the seven cases in which only normal parathyroids were identified, no fewer than three glands wer proven in each. Three patients have had subsequent mediastinal exploration and excision of an adenoma. This failure rate of cervical exploration (4%) is attributed to mediastinal adenomas, and a second adenoma, and incorrect diagnosis. An awareness of the frequency of ectopic adenomas and their usual locations is of considerable benefit to the surgeon. Identification of the normal glands is of great importance as the search for a specific missing gland (adenoma) can be conducted in a logical sequence based on anatomic and embryologic knowledge of the parathyroids.