Introduction
SURGICAL resection is the treatment of choice for the majority of patients with benign multinodular goitre (MNG). Current indications for surgery are compression-induced symptoms, suspected malignancy, hyperthyroidism and cosmesis. Surgical options for the management of IvING include bilateral subtotal thyroidectomy (BST), near total thyroidectomy (NTT – total lobectomy on the dominant side and a subtotal optimal surgical procedure for these patients the choice of surgical technique must take into account the potential benefits and complications of each procedure.
The main reason for performing BST is a presumed lower incidence of post-operative complications, including recurrent laryngeal nerve (RLN) palsy and hypoparathyroidism, and an attempt to achieve post-operative euthyroid status. However, there is a risk that the goiter will recur (9-435/) and an increased surgical morbidity during re-operation. Furthermore, a number of patients treated by sub-total thyroidectomy will still require thyroxin replacement following surgery.
There are increasing numbers of publications recommending TT for bilateral MNG. The authors who favour TT state that this operation has low complication rates in the hands of experienced thyroid surgeons and has an incidence of iatrogenic injuries that is similar to a subtotal procedure.
Discussion
In the presence of MNG, there are currently several options for the type of surgery that can be offered to these patients. In recent years there has been a change in the surgical treatment of multinodular thyroid disease, with an increasing number of surgeons performing total or near-total thyroidectomy. Following a decision to operate for MNG the advantages and disadvantages of each procedure should be considered and discussed with the patient to select the most appropriate procedure.
In several regions of Turkey, goitre is still an endemic disease and MNG patients constitute a large part of the workload of both general and endocrine surgeons. Since the clinical and pathophysiological evidence suggests that MNG affects the entire gland, any surgery that leaves potentially abnormal thyroid tissue in situ carries a risk of recurrent disease.
The popularity of BST for MNG is decreasing with time. It has the disadvantage of high recurrence rates and carries the risk for increased surgical morbidity during the course of re-operation. The incidence of recurrence after subtotal thyroidectomy varies in different studies and may be as high as 23%. The recurrence rate following BST is largely dependent on the length of follow-up, and has been reported as 42% in one study with thirty-year follow-up. Two patients (1.2% – 2/170) in this study experienced recurrent disease following BST, one of them 2 years and the other 2.5 years after the initial operations but the follow-up period is too short to make any comparison between BST, NTT and TT.
Re-operation for recurrent disease carries a significant risk of damage to both RLNs and the parathyroid glands and during completion thyroidectomy there is a ten-fold increase in iatrogenic injuries. As a general rule, the risk of complications increases with the number of re-operations performed. The re- operation rate in our study is 0.4% (31750). All three patients initially treated by BST underwent completion thyroidectomy for malignancy with no subsequent complication.
One potential reason for performing BST is the maintenance of euthyroid status without thyroxin replacement. It has been well documented, however, that to leave a small thyroid remnant in situ will not prevent the onset of hypothyroidism. This finding has been confirmed in our study with 100% of all patients treated by BST, for benign MNG, requiring at least 100 pg L-thyroxine daily. Furthermore, in the presence of unrecognized malignancy, BST may represent inadequate surgery. The incidence of occult malignancy is generally thought to be 7%-10%. The tumours are usually well-differentiated cancers and are often either papillary or follicular in nature. In this study the overall occult malignancy rate is 7.7% (58/750) and was noted to be lower in the BST group (4.7% – 8/170) because of the selection criteria of NTT or TT for nodules suspicious of malignancy. Moreover, malignant transformation in the thyroid remnant after subtotal resection ranges from 4% to17%.
The potential benefits of TT include adequate removal of the disease, prevention of recurrence, and avoidance of the need for completion surgery in the presence of occult malignancy. The only real argument against TT is the potential increase in the rate of complications.
There is no doubt that a well-trained endocrine surgeon can achieve extremely low complication rates, especially when using the technique of capsular dissection, staying close to the thyroid gland, and preserving the blood supply to the parathyroid glands, along with identification and preservation of the recurrent laryngeal nerve 1281 In addition further studies have demonstrated that surgical residents can perform TT just as safely as experienced endocrine surgeons, provided they have appropriate supervision. As a result the number of patients with MNG treated by TT is increasing and now exceeds 80%.
The three main complications following thyroid surgery include RLN palsy, hypoparathyroidism and postoperative hemorrhage. There were no patients in this study who required re-operation for hematoma. The reason for this may be one by one ligation of the each branch of the vessels of the superior and inferior pole close to the thyroid gland. In experienced hands the incidence of permanent RLN palsy ranges from 0 – 0.7% following TT and from 0-1.3% following BST. It has long been recognized that failure to recognize the RLN increases the risk of damaging it. The authors (SK & SA) are performing the described technique since 1992 for identifying the RLNs and the parathyroid glands. The permanent RLN palsy rate was low in all three groups in keeping with previous series by experienced surgeons and within current guidelines (permanent vocal cord palsy rate <1%) issued by the British Association of Endocrine Surgeons. There was no significant difference between these groups.
Every effort should be made to preserve parathyroid glands with their own blood supply however, this may not be sufficient to prevent the occurrence of transient hypoparathyroidism and transient post-thyroidectomy hypocalcemia, secondary to hypoparathyroidism, is common. Delbridge et al. state that transient hypoparathyroidism should be an accepted outcome of bilateral thyroid surgery rather than a complication. It is noted that the degree and duration of hypocalcemia increase with the extent of thyroid surgery. Our results concur with the literature with an incidence of temporary hypoparathyroidism increased with the extent of surgery (Table 1). There was, however, no difference in the rates of permanent hypoparathyroidism between the three groups (BST 0%; NTT 0%; TT 0.4%).
A number of patients in this series had near-total thyroidectomy. This procedure offers an alternative to TT by performing a total lobectomy on the dominant side and a subtotal lobectomy on the contra lateral side, leaving behind nearly 1-2 g of thyroid tissue on the less affected side. It has been suggested that this procedure combines the advantages of TT (no recurrences) with those of subtotal thyroidectomy (low incidence of transient and permanent hypoparathyroidism). However, Pappalardo et al, suggested that no advantages be offered by this procedure, when compared with TT, with the possible exception of a lower incidence of temporary hypoparathyroidism, which can easily be managed medically. Despite this we believe that there may be specific indications for this procedure especially when there is doubt about the integrity of RLN on the lobectomy side or when a patient may be at increased risk of hypoparathyroidism during the operation. In our series 42.6% (320/750) of cases had NTT as the initial operation for benign NI-NG. This was performed to remove the diseased thyroid gland, with a low recurrence rate, and to attempt to reduce the incidence of hypoparathyroidism and RLN palsy. In addition a small thyroid remnant renders it accessible to 1311 ablation if an occult cancer is found in the specimen and avoids re-operation for completion thyroidectomy. In this series there was a transition from NTT to TT as the surgeons realized that by careful dissection and appropriate surgical technique TT could be performed as safely as NTT. Although there is no recurrence in the NTT group, our follow-up period is too short to compare with TT at this stage.
It is known that retrospective reviews often fail to detect all cases and the retrospective design of the study may prevent any firm conclusion on the incidence of complications. However, considering the large number of patients included in this study, our results show that experienced endocrine surgeons performing total or near total thyroidectomy for benign MNG can achieve low permanent complication rates. We conclude that the operative skills and experience determine the complication rates rather than the type of operative procedure.
Reference:
Ozbas S, Kocak S, Aydintug S, Cakmak A, et al., “Comparison of the Complications of Subtotal, Near Total and Total Thyroidectomy in the Surgical Management of Multinodular Goitre”, Endocrine Journal, vol. 52, no. 2, pp. 199-205, 2005.
