Unilateral parathyroid exploration
Primary hyperparathyroidism is a common disease and many patients experience symptoms and demonstrate complications of their hypercalcaemia; surgical intervention in the form of cervical exploration is now being implemented with increasing frequency.
In a high proportion (80-90 per cent) of individuals the underlying pathological lesion is a solitary parathyroid adenoma. In the remaining patients multiglandular disease is present. The standard operative strategy has been bilateral neck exploration, attempted identification of all four parathyroids, and removal of obviously enlarged glands. This approach has resulted in unnecessary surgical exploration of the contralateral side of the neck in the great majority of patients whose hyperparathyroidism was caused by a solitary adenoma.
Against this background, unilateral cervical exploration for patients with a single parathyroid adenoma represents an attractive surgical option, if the side of the solitary tumour can be identified; this may occur either by chance at operation (i.e. on the first side exposed) or before surgery using ultrasonographic or scintigraphic localization techniques.
The philosophy of unilateral parathyroid exploration was first expounded by Roth and colleagues' and developed by Tibblin and associates'. Both of these groups practised blind exploration of the neck with termination of the operation if an adenoma was located on the side initially explored. Compared with patients who underwent bilateral cervical exploration, Tibblin et al. found that those who had a unilateral operation experienced less hypocalcaemia after surgery and had a significantly shorter mean operation time'. More important, no patient who underwent unilateral exploration experienced recurrent hypercalcaemia during a follow-up of between 2 and 7 years.
The availability of non-invasive localization techniques, such as ultrasonography and, particularly, thallium-technetium isotope subtraction scanning, now allows accurate lateralization of a significant proportion of solitary parathyroid adenomas before operation. In this hospital thallium-technetium scanning has been used routinely since 1983 for patients who are about to undergo neck exploration for primary hyperparathyroidi~m~. After experience with the investigation developed, and with an awareness of the very high incidence of single adenoma in this disease, a prospective study of scan-directed unilateral parathyroid exploration for those patients who had a positive scan was started. Such a surgical approach produced encouraging results in a small series of patients reported by Biller and colleagues4 in 1986.
Since 1985 the surgical strategy, for patients coming to first-time cervical exploration for primary hyperparathyroidism and who have an isotope scan showing a single 'hot-spot', has involved a scan-directed unilateral operation with removal of the parathyroid adenoma and biopsy of the ipsilateral normal gland. Bilateral cervical exploration is performed if: (1 ) the isotope scan fails to demonstrate an adenoma;
( 2 ) the scan shows more than one 'hot-spot'; ( 3 ) two enlarged parathyroids are encountered on the side initially explored; or ( 4 ) familial hyperparathyroidism or multiple endocrine neoplasia is suspected. If an adenoma is not located on the side suggested by the scan, exploration of the contralateral side of the neck is, of course, carried out. This policy has resulted in a significant reduction in operating time for those patients submitted to unilateral exploration (mean 26 min) and, critically, leaves them no more vulnerable to persistent or recurrent hypercalcaemia than those undergoing standard bilateral cervical exploration5. It is acknowledged that the isotope subtraction scan will prove to be of positive help in guiding the surgeon to the site of the tumour in only 55-60 per cent of patients with solitary parathyroid adenoma, but this is not a reason for failing to use the scan information for those individuals in whom the investigation is positive. The logic of a scan-directed but routine bilateral cervical exploration for patients with a single parathyroid adenoma is difficult to follow6.
The advantages of unilateral parathyroid exploration for solitary adenoma include not only a reduced operating time without jeopardizing the potential for cure, but also elimination of the risk of recurrent laryngeal nerve and parathyroid injury on the unexplored side and, possibly, a consequent reduction in the incidence of hypocalcaemia after operation. Opponents of the philosophy of unilateral exploration