Aim: Therapy for endemic goitre after surgical resection depends on the residual thyroid volume. Post-operative changes have been known to impair the fundamental sonographic evaluation of residual thyroid tissue. It was our aim to determine whether THI is a feasible method for thyroid volumetry after surgery.
Methods: 48 patients underwent thyroidectomy, hemithyroidectomy, near total resection, or partial resection of the thyroid gland. In all patients THI of the neck was performed 4 (mean; range: 2-7 days) days after surgery using an Elegra sonographic device (Siemens, Erlangen, Germany) with a transmitted frequency of 3.4 MHz and received frequency of 6.8 MHz. The examiner was blinded to the patient's diagnosis and the type of surgery. The residual tissue volume measured by means of THI and intra-operative volumetry were both compared to sonographic volumetry 12 weeks after surgery, the latter serving as the gold standard. Accuracy of THI and intraoperative volumetry were tested for significant differences using a paired t-test.
Results: Volumetry by the surgeon was available in 26 patients (54%). The men error of THI volumetry was 2.4 ml (SD: 3.3 ml; maximum: 17 ml). The mean error of intraoperative volumetry was 1.4 ml (SD: 1.9 ml; maximum: 6 ml). The mean difference between THI and intraoperative volumetry was 1 ml (SD: 2.7 ml; maximum: 7 ml; p = 0.085).
Conclusions: THI permits early volumetry of the residual tissue after thyroid surgery comparable with the intraoperative volumetry. Thus, THI may be helpful in guiding the substitution of thyroid hormones.