A four-gland exploration is described. Image guided selective neck exploration is being more frequently employed. This procedure is not described or illustrated. The right lobe is freed by blunt index finger dissection (Chapter 115, figures 19 and 20) in preparation for identification of the course of the recurrent laryngeal nerve and the tan/yellow-colored parathyroid glands at the upper and lower poles of the thyroid gland. After the two glands on the right side have been identified, a similar search is made on the left side. The parathyroid glands may appear normal or only slightly enlarged when hyperplasia is involved, especially in the MEN I syndrome. A solitary adenoma, when found, may be the size of a small marble or several centimeters in diameter.
Further mobilization of the right lobe results when the middle thyroid vein is ligated and tied (figure 2). A small hemostat is used to grasp the thyroid and retract it upward and medially. The surgeon may retract the thyroid with the left thumb over a piece of gauze on the upper pole of the thyroid. The relationship of the recurrent laryngeal nerve to the middle thyroid artery and the arterial blood supply to the upper pole of the thyroid should be clearly verified (figure 3). The loose tissue is gently pushed aside with forceps and gauze until the color identifiable as parathyroid is visualized.
Many times it is difficult to be certain whether discolored tissue is the parathyroid or a hematoma in fatty tissue. Using fine-tooth forceps, the adenoma, if identifiable, is very carefully dissected from the adjacent tissue, constantly keeping in mind the location of the recurrent laryngeal nerve (figure 3). Time is required to develop the rather frail vascular pedicle going to the superior parathyroid, which is double-clamped and ligated (figure 4).
A portion of a gland may be excised for immediate frozen-section examination to determine that it is parathyroid tissue. In some instances, a small biopsy may be taken from several areas believed to be parathyroid glands. A numbered diagram should be made of all biopsy sites along with the individual frozen-section reports of the specimens removed.
The extent of the operation should not be limited to the excision of one obviously enlarged gland that makes a gross diagnosis of adenoma quite likely. If a single enlarged gland is found and removed, repeat determination of a rapid PTH level should show a fall of at least 50% within 10 minutes or 85% by 15 minutes if this was the only abnormal gland. In a four-gland exploration, the other three glands should be identified and their locations recorded. Some prefer a biopsy verification of each one (figure 5), while others attach a fine, deep blue nonabsorbable suture to the gland remnant and bring a long end out into the subcutaneous tissue. The blue suture line serves as a visible guide to the site of the parathyroid biopsy should reoperation become necessary.
In patients with the familial MEN I syndrome, three normal-appearing glands may be excised as well as one-half of the fourth remaining gland. It is advisable to control any oozing with a small silver clip (figure 6) in order to ensure certain identification of the location of any remaining parathyroid tissue should hyperparathyroidism recur.
In rare patients with the familial MEN I syndrome, there is a disturbing rate of recurrent hyperparathyroidism because of the mutagenic potential of the MEN I syndrome. As a result, a radical parathyroidectomy leaving only one-half of one gland should be considered. Resection of the thymus should probably be considered, especially if one of the lower parathyroid glands is missing.
In general, in a patient with recurrent hyperparathyroidism after parathyroidectomy, the surgeon should assume that one or more glands in the cervical region have been overlooked or are aberrantly located or that the patient has the familial multiple neoplasia syndrome. Mediastinal involvement varies but may be present in as little as 2.5% of patients. Upper mediastinal tumors are usually intrathymic, near the innominate vein.
In patients with recurrent hyperparathyroidism, preoperative imaging is helpful if it presents good evidence that a tumor is present in the upper mediastinum. At operation, an effort is made to bring the thymus up into view above the suprasternal notch in the hope of finding a readily recognizable parathyroid gland within it. A transsternal approach to the thymus is rarely required.