Radiological and histological analysis of the structural changes in the rat parotid gland following release of Stensen's duct obstruction

Sialography is the preferred method for diagnosis and treatment planning in obstructive sialadenitis. Although many experimental studies have reported changes following duct obstruction, those following release of obstruction have not been examined. The present study was undertaken to clarify: (1) the relationship between sialographic and histological changes; (2) the effects of duration and pressure of obstruction on gland recovery; (3) the possibility of establishing those sialographic features which indicate the prognosis for gland recovery. Stensen's ducts of rat parotid glands were obstructed for two different periods and at three different pressures in order to induce varying degrees of degenerative changes in the gland. The structural alterations resulting from release of obstruction were investigated by means of qualitative and quantitative microsialography and histology. Gland structure was assessed visually from the latter and classified into six groups: normal, recovery, and slight, moderate and severe degeneration and fibrous. Microsialograms were evaluated based on these groups. Qualitatively, microsialograms of the operated glands had a stricture in the obstructed region and dilation of the major ducts. Histological differences between recovery and degeneration glands were reflected in the morphology of peripheral ducts. The former showed a branch-like morphology similar to that of the normal group, and the latter contained small granule-like structures. Quantitatively, dilation of major ducts in the recovery group decreased compared with the other operated groups. There were no distinct sialographic features in the degeneration and fibrous groups which correlated with the degree of degeneration observed histologically. Duration and pressure of obstruction were highly predictive for prognosis for recovery. However, it was difficult to determine the prognosis for gland recovery from sialographic findings at the time of release of obstruction.