Risks and consequences of incidental parathyroidectomy during thyroid resection

Background: Inadvertent removal of the parathyroid glands during elective thyroid surgery occurs more frequently in certain high-risk patients and can lead to symptomatic hypocalcaemia. Methods: A case-control study was carried out at a tertiary referral, academic medical centre between May 1994 and August 2001. Five hundred and thirteen patients underwent thyroid resection. Pathology reports were reviewed to identify patients who had the inadvertent removal of a parathyroid gland during their thyroid surgery. Thirty-three (6.4%) patients had inadvertent resection of a parathyroid gland. The outcomes of these 33 patients (INCIDENTAL) were compared with the other 480 patients who did not have resection of parathyroid tissue (NO INCIDENTAL). Results: Risk factors for inadvertent parathyroid resection included younger age (P = 0.003), bilateral thyroid resection (P = 0.001) and malignant pathology (P = 0.002). Factors that did not increase the risk of incidental parathyroidectomy included gland weight, sex, presence of a goitre, previous neck exploration and concurrent lymph node dissection. In the INCIDENTAL group 24% had a postoperative calcium levels less than 7.0 mg/dL (P = 0.001). Symptomatic hypocalcaemia developed in 12% of INCIDENTAL patients, compared to 4% in the NO INCIDENTAL group (P = 0.06). Conclusion: Incidental removal of parathyroid tissue occurred in 6.4% of thyroid resections. Younger patients undergoing a total or subtotal thyroidectomy for malignancy were at the highest risk. These patients had lower postoperative calcium levels, but the majority (88%) experienced no clinical consequences.