Frequency of ectopic and supernumerary intrathymic parathyroid glands in patients with renal hyperparathyroidism: analysis of 461 patients undergoing initial parathyroidectomy with bilateral cervical thymectomy.

BACKGROUND: The frequency of intrathymic parathyroid glands (IPGs) in patients undergoing parathyroidectomy for renal hyperparathyroidism (rHPT) varies considerably between 14.8% and 45.3%. Total parathyroidectomy with autotransplantation and subtotal parathyroidectomy are the most accepted surgical procedures to treat patients with rHPT. However, routine bilateral cervical thymectomy (BCT) is still discussed, although controversially.

METHODS: From a prospective database of patients who underwent parathyroid surgery for rHPT between 1975 and 2009, patients with routine BCT at initial PTX were further analyzed regarding the frequency of ectopic and supernumerary IPGs. Duration of hemodialysis and stage of chronic kidney disease were correlated with the frequency of supernumerary IPGs to elucidate a potential role of long-standing proliferation stimuli to any surplus parathyroid tissue.

RESULTS: Initial parathyroidectomy with BCT was performed in 461 patients. IPGs were resected in 205 of them (44.5%). They were ectopic in 181 (39.3%) and supernumerary in 30 patients (6.5%). The frequency of supernumerary IPGs in patients on permanent hemodialysis was 7.4% (29/392), 3.9% (1/26) in predialysis patients, and 0% (0/43) in patients after successful kidney transplantation. This differences reached no statistical significance.

CONCLUSIONS: BCT is essential in patients with fewer than four parathyroid glands identified at typical positions. Because of the low frequency of supernumerary IPGs and a suspected low proliferation stimulus, the relevance of BCT after resection of four glands in predialysis patients and those after successful kidney transplantation must be questioned. Nevertheless, routine BCT seems to be acceptable and can be recommended in patients on permanent hemodialysis not awaiting kidney transplantation until proven otherwise by prospective trials.