Surgical significance of undescended parathyroid gland in renal hyperparathyroidism

Background In renal hyperparathyroidism, in which basically all parathyroid glands are hyperplastic, overlooking one undescended parathyroid gland becomes important. Methods Between July 1973 and December 2004, 1750 patients in our department underwent parathyroidectomy for severely advanced renal hyperparathyroidism. We evaluated the frequency and location of undescended parathyroid glands and the clinical findings and the prognosis of patients with such glands. Results Undescended parathyroid glands in our series of renal hyperparathyroidism numbered 16 of 1750 cases (0.91%). In 9 patients, the glands were removed at the initial parathyroidectomy in our hospital. Two of these glands were detected by preoperative imaging; 6 glands were removed with an undescended thymus. The mean weight of the undescended parathyroid glands that were removed at initial operations was 470 mg (30 to 1392 mg). In 7 other patients, unrecognized undescended glands were responsible for persistent hyperparathyroidism in 6 patients and recurrent disease in 1 patient. In 4 of these 7 patients, the initial parathyroidectomy was performed at our hospital; in the other 3 patients, the initial parathyroidectomy had been done at another hospital, and the glands were removed on reoperation. The mean weight of these glands was 1295 mg (range, 444-2396 mg). In 12 of a total of 16 patients with undescended glands, there appeared to be an inferior parathyroid gland, and the other 4 glands appeared to be a superior gland. No glands were detected by sestamibi scans. Conclusion In operations for renal hyperparathyroidism, an undescended parathyroid gland can be readily overlooked, which leads to persistent or recurrent hyperparathyroidism. Because an undescended parathyroid gland is not always an inferior gland, in surgery for persistent and/or recurrent renal hyperparathyroidism, it is very important to examine carefully the submandibular portion to detect such an undescended gland.