Structural changes in the diaphragm under conditions of obstructive jaundice (an experimental study)

Obstructive jaundice is a prevalent condition in surgical wards. Despite the possibility of surgical removal of biliary obstruction, the high incidence of multiorgan damage during the postoperative period and the associated mortality remain significant challenges for clinical practice. The animal model of obstructive jaundice constitutes a significant component of the study of alterations in human organs, including the diaphragm. The aim of this study was to examine the impact of jaundice on the histological structure of the diaphragm, with a particular focus on the lumbar part, which is the most functionally important, and the costal and tendon components in the experimental rat model. The study was conducted on 30 adult rats weighing 225.0±20.0 g and aged 6 months. All animals were divided into 2 groups: intact and main. The intact group included animals that were not modeling with any pathological process. In the second group of animals, obstructive jaundice was modeling by ligation of the common bile duct, using laparotomic access under general anesthesia. The digital material was subjected using the software “Excel” and “STATISTICA” 5.5 using parametric methods for evaluating the obtained data. The results demonstrated significant destructive and degenerative alterations. In the main group, particular attention was directed towards circulatory disturbances in the microcirculatory system and medium-sized vessels. Capillaries, venules, and arterioles exhibited full blood content, accompanied by all indications of rheohemodynamic disorders, manifesting as blood stasis, erythrocyte sludge, and their parietal adhesion. The arterioles appeared to be thickened as a result of plasma saturation. The endothelium exhibited modifications, with the appearance of rounded cells with vacuolated cytoplasm. Some of these cells were exfoliated. Additionally, edema and smooth muscle dystrophy were observed in the vessel walls, with these changes being more pronounced in the lumbar part of the diaphragm. In the presence of jaundice, the tendon part of the diaphragm exhibited a distinct ratio of structural components compared to the intact group. The tendon layer demonstrated an increase in thickness, which was attributed to edematous loosening. The collagen fibres exhibited a tortuous appearance, and the unevenness of colour became more pronounced compared to the intact group. Additionally, increased cellular infiltration was observed, both diffuse and with the formation of focal infiltrates. The presence of macrophages was observed in the structure of infiltrates, alongside conventional cells. A statistically significant increase was identified in the morphometric parameters of the muscular part of the diaphragm, including the average diameter of the muscle fibre, the nuclei area, the cross-sectional area of the muscle fibre, and the nuclear-cytoplasmic ratio, in the primary group. Furthermore, under the conditions of experimental jaundice, microcirculation disorders with impaired rheohemodynamics, endothelial dysfunction, and dystrophic-destructive changes in the muscle and tendon components occur in parts of the diaphragm, and these are more severe in the muscles of the crus of diaphragm.