Gastro-intestinal tract

Abstract

These are a group of exocrine glands whose principal function is secretion of saliva into the oral cavity. The parotid and to a lesser extent submandibular glands have the ability to take up iodide and other anions of similar ionic radius (including pertechnetate) in sufficient concentration to be imaged. They also concentrate gallium, almost certainly by a different mechanism. The sublingual and minor salivary glands cannot be visualized in this way, but pertechnetate secreted into the oral cavity adheres to mucosal surfaces too firmly to be eliminated by rinsing the mouth with water. The appearance is easily misinterpreted as visualization of these glands. In contrast to thyroid, but like gastric mucosa, iodide once trapped is not organified in the salivary glands and therefore has no advantage for imaging over pertechnetate. Uptake is blocked by perchlorate and by atropine but salivary glands may still be visualized despite a dose of (stable) iodide sufficient to block pertechnetate uptake by thyroid.