Preoperative Lobe Volume on Ultrasound Can Determine Appropriate Incision Length for Minimally Invasive Thyroid Surgery

Deborah Brauser

September 29, 2009

September 29, 2009 (Palm Beach, Florida) — The preoperative thyroid lobe volume, as assessed by ultrasound, can be used to determine the appropriate incision length needed for minimally invasive nonendoscopic thyroid surgery, according to results of a new retrospective chart review.

This study was presented in a poster session here during the American Thyroid Association 80th Annual Meeting by investigative team member Austin P. Daly, BA, medical student from the Department of Otolaryngology, Head and Neck Surgery at Thomas Jefferson University in Philadelphia, Pennsylvania.

He told Medscape Endocrinology that previous studies have tried to define minimally invasive thyroid surgery by a specific incision size, with some classifying it as less than 6.0 cm and others at between 2.5 and 3.0 cm.

"In reality, a predetermined surgical incision size independent of thyroid variables is an unrealistic goal," said Mr. Daly. "The surgery should be defined by the minimal incision length required to remove a gland of a given size and should not be based on an absolute number."

He added that "with various advancements with ultrasound and with smaller incision sizes, we felt that being able to predetermine an incision length preoperatively would be very helpful for both preoperative and postoperative recovery."

In this study, the investigators sought to "correlate preoperative ultrasonic thyroid lobe dimensions with an appropriate preoperatively determined minimally invasive incision length."

They examined data from 71 patients (83% female; average age, 50.2 years; age range, 19 - 78 years) who underwent a thyroid ultrasound before undergoing minimally invasive nonendoscopic thyroid surgery between January 2007 and May 2009. Of these, 31 underwent a total thyroidectomy and 40 underwent a lobectomy.

Both ultrasonic preoperative thyroid lobe volumes and the operative incision lengths were analyzed in all patients.

Incision Length Correlates With Lobe Volume

Overall, Mr. Daly and his team found that the incision length was significantly different between the 2 groups (< .001).

After the median lobe volume was determined for those who had the thyroid lobectomy, this value was used to subdivide the patients into groups with lobe sizes of either less than 28.32 mL (n = 20) or more than 28.32 mL (n = 20).

The incision length of the first subgroup ranged from 2.0 to 3.8 cm (mean, 3.13 cm ± 0.53) and of the second subgroup ranged from 2.5 to 5.0 cm (mean, 3.7 cm ± 0.71). The incision size difference between the 2 subgroups was significant (t test, < .01).

"Our data show that 50% of the thyroid lobes in the first subgroup were removed by an incision that was less than 3.1 cm, and 95% of the lobes this size were removed by an incision less than 3.6 cm," explained Mr. Daly.

The total thyroidectomy patients were also subdivided, with groups having a median total thyroid volume of either less than 49.24 mL (n = 16) or more than 49.24 mL (n = 15).

In the smaller volume group, the incision length ranged from 2.5 to 4.0 cm (mean, 3.4 cm ± 0.53). In the larger volume subgroup, length ranged from 3.6 to 6.0 cm (mean, 5.1 cm ± 0.99).

"Again, the incision length correlated with the thyroid lobe volume on ultrasound [t test, P < .00001]," reported Mr. Daly. "Also, 50% of the thyroid glands less than 49.24 mL were removed with an incision that was less than 3.4 cm, and 95% of the thyroid glands less than this size were removed with an incision less than 3.9 cm. These numbers represent a point of reference and provide the preliminary data necessary for further research."

Just a Starting Point

In further analyses of all the patients, a strong correlation was found between the largest thyroid lobe volume and incision size (r = 0.73), and a moderate correlation was found between the largest lobe dimension and incision size (r = 0.51).

"Our study suggests that in preparation for thyroid surgery, surgeons can use thyroid lobe volumes as determined by preoperative ultrasound to assist in planning an optimal incision length for removal of the gland," said Mr. Daly.

"In our opinion, there are no absolute contraindications to a minimally invasive approach, including large gland size," he continued. "Instead, the appropriate incision length necessary to remove that gland should be accepted as minimally invasive."

Mr. Daly reported that the next step in their study is to increase the patient numbers and to correlate incision length with ultrasonographic lobe volume. "This is just a starting point," he said. "In the future, for every 10 mL increase in thyroid lobe volume, we would like to be able to correlate an appropriate incision length for safe removal of the gland."

A Novel Approach

"I think this study confirms what a lot of surgeons have found as we've changed the technique of thyroidectomy, over the past 15 or 20 years, from using a longer incision of 10 to 12 cm to remove the entire thyroid gland to a much smaller incision," said Gerard M. Doherty, MD, professor of surgery, section head of general surgery, and chief of the Endocrine Surgery Division at the University of Michigan Health Systems in Ann Arbor, in an interview with Medscape Endocrinology.

Dr. Doherty, who was not involved with this study, is also the current secretary-treasurer of the International Association of Endocrine Surgeons.

"In the old way of making a larger incision that many of us trained in, we could expose everything all at once and make it all visible, but that was actually not necessary. We now make a smaller incision so that we can see everything we need to see," said Dr. Doherty.

"The approach in this study is a very novel way to determine incision length objectively with the thyroid lobe volume by ultrasound," noted Dr. Doherty. "It reflects another trend in thyroid surgery of actively using ultrasound in the office and in the operating room to help with the clear management of the patients."

He added: "I think this is important information for the people who do thyroid surgery to have and to know that there's another way they can use ultrasound as they try to figure out how big an incision is needed for a patient."

Mr. Daly and Dr. Doherty have disclosed no relevant financial relationships.

American Thyroid Association (ATA) 80th Annual Meeting. Abstract: Short Call Poster 13. Presented September 24, 2009.

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