title: Enhanced ALA-induced fluorescence in hyperparathyroidism.
abstract: BACKGROUND
  Intraoperative localization of parathyroid glands can be challenging especially in minimally invasive surgery. Fluorescence diagnosis using the photosensitizer aminolevulinic acid (ALA) has been described to identify normal parathyroid glands during experimental bilateral neck exploration. The present study evaluated fluorescence differences between hyperplastic and normal parathyroid glands as a precondition for a clinical application of the technique.
  
  
  METHODS
  Polycystic kidney disease (PKD) rats with hyperparathyroidism due to hyperplastic parathyroid glands and Wistar rats with normal parathyroid glands were photosensitized by peritoneal lavage with ALA solution. After surgical exposure of thyroid and parathyroid glands the operative site was observed under blue light conditions using the d-light system to assess fluorescence characteristics of each tissue. Fluorescence intensities of parathyroid glands and surrounding thyroid tissue were measured by spectrometry. Parathyroid hormone in serum of the rats was determined by enzyme-linked immunosorbent assay (ELISA).
  
  
  RESULTS
  Observation of the exposed thyroid site showed a subjectively stronger red fluorescence of the parathyroid glands in the PKD rats in comparison to the Wistar rats, whereas thyroid tissue appeared equally fluorescent. In the PKD animals, spectrometric fluorescence intensity was 10 times higher in the parathyroid glands than in the thyroid gland, whereas in the Wistar rats the ratio was 3.2:1. Fluorescence intensity in the parathyroid glands was more than twice in the PKD rats than in the Wistar rats, however slightly lower in the thyroid tissue. ELISA confirmed the pathophysiological change of a hyperparathyroidism with significantly increased serum levels of parathyroid hormone in the PKD rats.
  
  
  CONCLUSIONS
  Hyperparathyroidism enhances ALA-induced fluorescence of the parathyroid glands. A combined surgical fluorescence strategy may justify a unilateral, minimally invasive approach in selected patients and serve to improve the capability of the surgeon to safely and efficiently manage parathyroid diseases.
authors.affiliation: Department of Surgery, University Hospital Mannheim, Ruprecht-Karls-University of Heidelberg, Theodor-Kutzer-Ufer 1-3, 68167 Mannheim, Germany. ruediger@prosst.de
authors.forename: Ruediger L
authors.initials: RL
authors.lastname: Prosst
authors.forename: Lioba
authors.initials: L
authors.lastname: Schroeter
authors.forename: Johannes
authors.initials: J
authors.lastname: Gahlen
mesh_terms: D000622:Aminolevulinic Acid; D000818:Animals; D005453:Fluorescence; D006961:Hyperparathyroidism / Q000175:diagnosis* / Q000601:surgery; D017319:Photosensitizing Agents; D051381:Rats; D017208:Rats, Wistar; D013050:Spectrometry, Fluorescence / Q000379:methods
chemical_list: D017319:Photosensitizing Agents; D000622:Aminolevulinic Acid