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


METHODS
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.
Ruggieri
M
M
Department of Surgery Francesco Durante, University of Rome La Sapienza, Viale del Policlinico 00161, Rome, Italy. massimo.ruggieri@uniroma1.it
Fumarola
A
A
Straniero
A
A
Maiuolo
A
A
Coletta
I
I
Veltri
A
A
Di Fiore
A
A
Trimboli
P
P
Gargiulo
P
P
Genderini
M
M
D'Armiento
M
M
D000328:Adult; D002921:Cicatrix / Q000209:etiology; D004954:Esthetics; D005260:Female; D005500:Follow-Up Studies; D006044:Goiter, Nodular / Q000000981:diagnostic imaging* / Q000601:surgery*; D006801:Humans; D006980:Hyperthyroidism / Q000000981:diagnostic imaging* / Q000601:surgery*; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D019060:Minimally Invasive Surgical Procedures / Q000379:methods*; D009929:Organ Size / Q000502:physiology; D010147:Pain Measurement; D010149:Postoperative Pain / Q000209:etiology; D011183:Postoperative Complications / Q000209:etiology; D013961:Thyroid Gland / Q000000981:diagnostic imaging* / Q000473:pathology*; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging* / Q000601:surgery*; D016606:Thyroid Nodule / Q000000981:diagnostic imaging* / Q000601:surgery*; D013965:Thyroidectomy / Q000379:methods*; D014463:Ultrasonography