Ultrastructural changes of peritoneal lining cells in uremia

Some thirty years ago, peritoneal dialysis (PD) became a respectable modality of renal replacement therapy. That is why peritoneal membrane attracted the interest of investigators. Uremia is followed by changes in the morphology of serous membranes (uremic serositis). Uremic effects on pleura and pericardia have been studied for a long time, but the peritoneum is affected as well. The aim of our study was to examine the morphology of the peritoneum in uremic patients before the start of PD and to compare the findings with those from examinations of peritoneum in healthy controls. We examined 12 uremic patients and 10 healthy controls (kidney donors). Biopsies were taken from parietal peritoneum. The samples were prepared in the standard way for study by transmission electron microscopy (TEM). Certain pathological changes--deformation of mesothelial cells, their detachment from the basement membrane, and unusual bulging of apical surface--were identified at the light microscopy level on semi-fine sections. Paracrystalline intracytoplasmic inclusions were seen in mesothelial cells only by TEM. We hypothesize that the inclusions were causing deformation of the mesothelial cells and detachment of those cells from the basement membrane. Sacculate dilatations of rough endoplasmic reticulum (RER) cisternae with partly destroyed membranes and few ribosomes were also seen, with and without densely osmiophilic filaments within cisternae. Although these changes are mentioned in the literature, the exact reason for their appearance remains unknown.