Incidental parathyroidectomy during total thyroidectomy is not a direct cause of post-operative hypocalcaemia

BACKGROUND: Post-operative hypocalcaemia is the most common complication after total thyroidectomy, with a reported incidence of transient hypocalcaemia up to 50% and permanent hypocalcaemia 1.5-4%. The impact of incidental parathyroidectomy (IPE) on post-operative hypocalcaemia remains controversial. This study evaluated the risk factors for IPE following total thyroidectomy and compared post-operative calcium levels serially between patients with and without IPE. METHODS: A retrospective analysis of patients undergoing total thyroidectomy from January 2009 to October 2016 at Western Health was conducted. Histopathology reports were reviewed to identify specimens that included parathyroid tissue. Risk factors and dichotomous data were analysed by exact test of difference in binomial proportions. Group comparison of serial calcium levels (preoperative to 48 h post-operative) between the no IPE and IPE patients were analysed by calculating the area under the curve producing a time series summary. RESULTS: Four hundred and sixty-eight patients were included: 395 were females (81%), with a median age of 51 years. IPE was confirmed histologically in 84 patients (17.7%) and was more likely to occur in patients undergoing total thyroidectomy with central neck dissection (P = 0.0003), and in patients with malignant disease (P = 0.0005). The difference in area under the curve for serial post-operative calcium levels between the no IPE and the IPE groups was 0.61 (P = 0.21, 95% confidence interval: -0.37 to 1.58). CONCLUSION: Total thyroidectomy for malignancy and with central node dissection had a higher risk of IPE but did not result in significant changes in post-operative serum calcium levels