-Original-

Identification of Pathological and Normal Parathyroid Tissue by Fluorescent Labeling with 5-aminolevulinic Acid during Endocrine Neck Surgery

Shingo Takeuchi², Kazuo Shimizu¹, Kazuhide Shimizu Jr³, Haruki Akasu¹ and Ritsuko Okamura¹

¹Department of Endocrine Surgery, Nippon Medical School
²Department of Thoracic Surgery, Nippon Medical School
³Department of Neurosurgery, Tokyo Medical and Dental University

Background: When performing parathyroid or thyroid surgery, surgeons must distinguish parathyroid tissue from the surrounding thyroid tissue, to preserve healthy parathyroid tissue while excising diseased thyroid tissue or to completely remove pathological parathyroid lesions. Here, we explored the feasibility of labeling the parathyroid glands for easy identification by administering 5-aminolevulinic acid (5-ALA) orally to patients undergoing endocrine neck surgery, because 5-ALA accumulates in the parathyroid and has a fluorescent metabolite, protoporphyrin IX.
Methods: Twenty-nine patients about to undergo endocrine (parathyroid or thyroid gland) neck surgery were orally given 5-ALA, a nontoxic substance that occurs naturally in the human body and has no known major side effects. During surgery, we used blue light to excite protoporphyrin IX, the fluorescent metabolite of 5-ALA, and viewed the resulting bright red fluorescence through an optical filter.
Results: In the majority of the patients, the parathyroid glands were defined by a clear fluorescence. In 23 patients with pathological parathyroid tissue, the fluorescence enabled us to identify and completely remove diseased parathyroid tissue. In 3 patients with thyroid disease, we were able to easily remove diseased thyroid tissue, and an accidentally removed parathyroid gland was autotransplanted during surgery.
Conclusions: In all but a few cases, 5-ALA clearly labeled parathyroid tissue, allowing for its clean removal or preservation according to the purpose of the surgery. This simple, benign technique is extremely useful for identifying parathyroid tissue, whether pathological or normal, during endocrine neck surgery.

J Nippon Med Sch 2014; 81: 84-93

Keywords
5-aminolevulinic acid, parathyroid, fluorescent labeling, video-assisted neck surgery, video-assisted thoracic surgery

Correspondence to
Kazuo Shimizu, Department of Endocrine Surgery, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8602, Japan
shimizukazuomdfacs@yahoo.co.jp

Received, November 1, 2013
Accepted, December 9, 2013