The estimation of the thyroid volume before surgery--an important prerequisite for minimally invasive thyroidectomy

Langenbecks Arch Surg. 2008 Sep;393(5):721-4. doi: 10.1007/s00423-008-0399-y. Epub 2008 Aug 9.


Introduction: Actually, thyroid volume >25 ml, obtained by preoperative ultrasound evaluation, is a very important exclusion criteria for minimally invasive thyroidectomy. So far, among different imaging techniques, two-dimensional ultrasonography has become the more accepted method for the assessment of thyroid volume (US-TV). The aims of this study were: (1) to estimate the preoperative thyroid volume in patients undergoing minimally invasive total thyroidectomy using a mathematical formula and (2) to verify its validity by comparing it with the postsurgical TV (PS-TV).

Materials and method: In 53 patients who underwent minimally invasive total thyroidectomy (from January 2003 to December 2007), US-TV, obtained by ellipsoid volume formula, was compared to PS-TV determined by the Archimedes' principle. A mathematical formula able to predict the TV from the US-TV was applied in 34 cases in the last 2 years.

Results: Mean US-TV (14.4 +/- 5.9 ml) was significantly lower than mean PS-TV (21.7 +/- 10.3 ml). This underestimation was related to gland multinodularity and/or nodular involvement of the isthmus. A mathematical formula to reduce US-TV underestimation and predict the real TV was developed using a linear model. Mean predicted TV (16.8 +/- 3.7 ml) perfectly matched mean PS-TV, underestimating PS-TV in 19% of cases. We verified the accuracy of this mathematical model in patients' eligibility for minimally invasive total thyroidectomy, and we demonstrated that a predicted TV <25 ml was confirmed post-surgery in 94% of cases.

Conclusions: We demonstrated that using a linear model, it is possible to predict from US the PS-TV with high accuracy. In fact, the mean predicted TV perfectly matched the mean PS-TV in all cases. In particular, the percentage of cases in which the predicted TV perfectly matched the PS-TV increases from 23%, estimated by US, to 43%. Moreover, the percentage of TV underestimation was reduced from 77% to 19%, as well as the range of the disagreement from up to 200% to 80%. This study shows that two-dimensional US can provide the accurate estimation of thyroid volume but that it can be improved by a mathematical model. This may contribute to a more appropriate surgical management of thyroid diseases.

MeSH terms

  • Adult
  • Cicatrix / etiology
  • Esthetics
  • Female
  • Follow-Up Studies
  • Goiter, Nodular / diagnostic imaging*
  • Goiter, Nodular / surgery*
  • Humans
  • Hyperthyroidism / diagnostic imaging*
  • Hyperthyroidism / surgery*
  • Linear Models
  • Male
  • Middle Aged
  • Minimally Invasive Surgical Procedures / methods*
  • Organ Size / physiology
  • Pain Measurement
  • Pain, Postoperative / etiology
  • Postoperative Complications / etiology
  • Thyroid Gland / diagnostic imaging*
  • Thyroid Gland / pathology*
  • Thyroid Neoplasms / diagnostic imaging*
  • Thyroid Neoplasms / surgery*
  • Thyroid Nodule / diagnostic imaging*
  • Thyroid Nodule / surgery*
  • Thyroidectomy / methods*
  • Ultrasonography