Morphological studies of mesothelial cells in CAPD effluent and their clinical significance

We studied the mesothelial cells in the effluent of patients undergoing continuous ambulatory peritoneal dialysis (CAPD) and their relationship with CAPD duration, peritoneal function, peritoneal sclerosis (PS), and sclerosing encapsulating peritonitis (SEP) in 49 patients (26 men, 23 women) treated for 3 to 161 months with CAPD. Three patients had SEP and five patients had PS. The overnight effluent was drained and centrifuged. The cell differentiation and surface area of mesothelial cells were studied by a computed light microscope system after cytospin preparation staining. The surface area of 50 cells was measured. The mesothelial cells were classified into three types according to their morphological appearance: normal cell type, with a mean surface area of 335.6+/-31.0 microm2 and mean nucleocytoplasmic ratio (N/C ratio) of 0.66+/-0.01; dyskaryotic cell type, with a mean surface area of 570.5+/-35.9 microm2 and N/C ratio 0.58+/-0.06; and giant cell type, with a mean surface area of 1,821.0+/-68.8 microm2 and N/C ratio of 0.06+/-0.01. There was a low but significant correlation between the fast peritoneal equilibration test and surface area (r=0.495; P=0.0120) and a highly significant correlation between CAPD duration and mean surface area (r=0.719; P < 0.0001). This increased cell surface area was because of both an increased surface area of normal and dyskaryotic cells and an increase in the number of dyskaryotic and giant cells. The mean surface area in patients with SEP was 709.3+/-125.4 microm2 and that in patients with PS was 586.6+/-55.2 microm2. Giant cells were found in the effluent of all three patients with SEP and three of the patients with PS. In conclusion, a marked correlation was found between the surface area of effluent mesothelial cells and the duration of CAPD. Giant cells were almost always found in the effluent of patients with SEP and PS. The surface area of mesothelial cells in the effluent might reflect morphological changes in the peritoneum during CAPD. These morphological changes and the measurement of the size of mesothelial cells may predict critical derangement of peritoneal membrane.