A morphologic study of the recovery of the rat submandibular gland after retrograde infusion. I. Water-soluble radiographic contrast medium

Enigmatic Formations Found in Routine Orthopantomography (OPG) Examinations: A Case Report

We describe two clinical cases of occasional radiographic findings on orthopantomography (OPG) that were performed routinely, for which the definitive diagnosis may be uncertain. After an accurate remote and recent anamnesis, for reasons of exclusion, we hypothesize a rare case of the retention of a contrast medium in the parenchyma of the major salivary glands (parotid, submandibular, and sublingual) and their excretory ducts as a consequence of sialography examination. In the first case we analyzed, we found it difficult to classify the radiographic signs on the sublingual glands, left parotid, and submandibular, while in the second case, only the right parotid was involved. Using CBCT, the spherical findings were highlighted, with multiple having different dimensions, as well as radiopaque in their peripheral portion and more radiolucent inside them. We could immediately exclude salivary calculi, which usually have a more elongated/ovoid shape and appear homogeneously radiopaque without radiolucency areas. These two cases (of hypothetic medium contrast retention with unusual and atypical clinical-radiographic presentation) have very rarely been comprehensively and correctly documented in the literature. No papers have a follow-up longer than 5 years. We conducted a review of the literature on the PubMed database, finding only six articles reporting similar cases. Most of them were old articles, demonstrating the low frequency of this phenomenon. The research was performed using the following keywords: "sialography", "contrast medium", "retention" (six papers) and "sialography", and "retention" (13 papers). Some articles were present in both searches, and the really significant ones (defined after a careful reading of the entire article and not only of the abstract) resulted only in six occurrences in a time span from 1976 to 2022.

Experimental sialography: the effects of retrograde infusion of radiographic contrast media on salivary gland morphology and function. A review article

An experimental model for sialography, involving retrograde infusion of contrast medium into the rat submandibular gland under continuous pressure monitoring, was developed. Morphologic alterations induced during infusion of water- and lipid-soluble radiographic contrast media and the distribution of the media were examined with light and electron microscopy. An uneven distribution of the media throughout the tissue and variations in the degree of the alterations in different parts of the gland were seen at all stages of filling. The changes primarily consisted of dilation of the luminal system, which successively became more pronounced as infusion continued. Infusion of the lipid-based medium consistently resulted in more severe alterations, including changes in the acini. Tracer studies showed that the water-soluble medium leaked out through the intercellular spaces and to the surrounding tissue, whereas the lipid-based medium appeared to be confined to the luminal space. Ductal filling with either medium resulted in a relatively fast recovery; after prolonged infusion, recovery was slower and additional alterations occurred. The acini showed confluence of secretory granules and vacuole formation. After infusion of the lipid-based compound, autophagic vacuoles and granulomatous alterations developed. Prolonged infusion with either medium resulted in atrophy of the parenchyma and connective tissue proliferation in some glands. An inflammatory infiltrate was present in all glands during the recovery period. Functional alterations, primarily consisting of a decrease in flow rate, were noted after prolonged infusion. The increase in intraluminal pressure induced during infusion was most likely the primary cause of the alterations. In addition, the presence of contrast medium contributed to the long-term effects of the procedure.

Saliva secretion from the rat submandibular gland after retrograde infusion of radiographic contrast media

Rat submandibular saliva was collected at various times after retrograde infusion of water-soluble (Renografin 60%) or lipid-soluble (Lipiodol UF) radiographic contrast medium. Significant alterations in flow rate occurred following heavy parenchymal filling with both types of contrast media. Occasional changes in protein concentration, lactoperoxidase activity, and K+ levels were also noted. These changes were relatively mild and transient, and gland function had generally returned to normal by one wk after infusion. No alterations in glandular function were detected after infusion of contrast medium to a degree (ductal filling) comparable to that usually employed in clinical sialography.

A morphologic study of the recovery of the rat submandibular gland after retrograde infusion. II. Lipid-soluble radiographic contrast medium

Lipid-soluble radiographic contrast medium was infused retrogradely through the main excretory duct of the rat submandibular gland until ductal and slight parenchymal filling or heavy parenchymal filling was achieved, as determined by the developing intraglandular pressure. The glandular tissue was fixed by vascular perfusion at different times following infusion, and examined by light and electron microscopy. Dilation of the intralobular ducts and scalloping of the luminal border were pronounced after both degrees of filling. Widening of the acinar lumina and intercellular canaliculi occurred early. Masses of fused secretory granules were commonly seen in the cytoplasm of the acinar cells and formation of vacuoles occurred frequently. In some acinar cells, densely packed granules filled the major part of the cytoplasm. Large lysosomes and autophagic vacuoles, frequently present in the various parenchymal cells, often contained apparent contrast medium. In addition, widening of the intercellular spaces between parenchymal cells was seen, particularly in the acini and intercalated ducts. An inflammatory cell-infiltrate, primarily comprised of polymorphonuclear leukocytes, was particularly prominent at 20 h and 30 h after infusion. The changes were generally more pronounced and persisted for a longer time in glands subject to heavy parenchymal filling. Large cyst-like spaces surrounded by inflammatory cells were seen in the lobules and in the interlobular connective tissue of these glands. At later times, areas containing apparent contrast medium surrounded by macrophages, were frequently observed in the connective-tissue stroma. Atrophy of the parenchymal cells was seen later, after heavy parenchymal filling, and a proliferation of the connective tissue had occurred. The changes were most probably caused by the elevated intraglandular pressure induced during infusion, and the subsequent cell damage and inflammatory reaction. A foreign body reaction, induced by the retained lipid-soluble contrast medium, was probably partly responsible for the morphological alterations observed, following infusion.