Technical Aspects in Studying Peritoneal Morphology in Animal Models of Peritoneal Dialysis

Abstract

Objective Peritoneal biopsies are considered useful for gaining a better understanding of the pathophysiology of the peritoneum during experimental peritoneal dialysis (PD). Different peritoneal tissue samples (i.e., abdominal wall, liver, diaphragm, intestine, and omentum) may be used, but there can be artifacts due to peritoneal tissue processing. Aim To investigate differences in peritoneal membranes from different parts of the peritoneum, and also 2 different fixatives, in experimental PD and a peritonitis model in rats. Methods Peritoneal tissues from the anterior abdominal wall, liver, omentum, and intestine were taken from each of 3 groups of animals: sham, experimental PD, and peritonitis model. Tissue samples were immediately fixed with 4% formaldehyde and routinely processed for histological examination. Two parietal peritoneal tissue samples according to longitudinal and horizontal sections of anterior wall inner abdominal muscle were also taken. All samples were immediately fixed with 4% formaldehyde and B5 fixative (B5), and then routinely processed for histological examination. Results In all groups, histopathological findings were more commonly seen in the abdominal wall samples. There were no changes observed in peritoneal membranes other than those of anterior abdominal wall samples from both sham and PD model rats. However, there was a significant difference between anterior and posterior facets of liver in the peritonitis model. Furthermore, the antimesenteric site of intestinal peritoneum was less affected than the mesenteric site. There were no significant histopathological differences between B5 and 4% formaldehyde fixation ( p > 0.05). Conclusion Our results suggest that peritoneum obtained from the anterior abdominal wall is the most affected area and therefore the most suitable site to investigate peritoneal changes in the experimental rat PD model. There were no significant differences between fixation with 4% formaldehyde and B5 solution. Abdominal wall samples should be of the same direction of inner abdominal muscle, that is, horizontal sectioning should be used for measurements of the submesothelial area.

Proposal of peritoneal biopsy procedures for patients undergoing peritoneal dialysis

“…Additionally, there is a need to establish a biopsy area and fixation method for precise morphological examination of biopsy specimens. In an earlier study on experimental PD rat models, Duman et al [10] reported that the peritoneum obtained from the anterior abdominal wall was the most affected area and that there were no significant differences between fixation with 4% formaldehyde and B5 solution. Referring to this article, we sampled the parietal peritoneum of the anterior abdominal wall near the surgical wound, and the sampling site becomes almost always the same.…”

“…To the best of our knowledge, only a few studies have reported on the methodology of peritoneal biopsy [7][8][9][10]. Moreover, a detailed biopsy procedure has been described in only one study [7], where the authors have proposed a suture method for collecting peritoneal samples.…”

“…2g-i) [11]. The peritoneal wall anchor technique reportedly improves the catheter survival rate [10], although the catheter is blindly fixed to the abdominal wall at the area inferior to the catheter insertion in the absence of peritoneal biopsy. However, in addition to the aforementioned advantage [11], the present method employing biopsy area allows for the fixation of the catheter to the abdominal wall in a safe and simple manner.…”

Animal models in peritoneal dialysis

“…Among the technical problems that have to be faced when handling animal models, tissue-sampling problems must be highlighted. The peritoneal tissue is quite fragile, dries quickly when exposed to the air and can easily be damaged even after delicate contact with surgical gloves or instruments (Duman and Sen, 2009 ). Furthermore, in patients on PD the visceral peritoneum exhibits more pronounced alterations than the parietal peritoneum, while in many of the studies conducted in animal models the biopsy samples are obtained by the parietal peritoneum.…”