Adaptation of the small intestine mucosa after gastric bypass surgery with a single anastomosis

Objective. To compare the morphological and morphometric changes of the small intestine mucosa in its common and biliopancreatic loops at different times after gastric bypass surgery with a single anastomosis. Materials and methods. The study included 36 patients who received surgical treatment at the Department of Thoracoabdominal Surgery of the Shalimov National Research Center for Surgery and Transplantation of the National Academy of Medical Sciences of Ukraine for morbid obesity, which consisted of gastric bypass surgery with a single anastomosis in various variants (long–loop, distal, mini–gastric bypass) in the period from 2016 to 2022. Further outpatient follow–up included scheduled endoscopic examinations at 3, 12, and 24 months after surgery. Results. At 3 months after the operation, no morphological and morphometric changes were detected in the studied biopsies of the mucous membrane of the biliopancreatic and common loops of the small intestine. The first morphological and morphometric changes in the small intestinal mucosa were observed 12 months after surgery. There was a statistically significant (p < 0.05) difference in the length of intestinal villi in the common and biliopancreatic loops of the small intestine – (0.390 ± 0.199) and (0.377 ± 0.184) mm, respectively. These changes indicate hypertrophy of villi in the colon to increase the absorption area. The thickness of the basal layer was greater in the biliopancreatic loop than in the total loop and amounted to (0.196 ± 0.068) and (0.167 ± 0.043) mm, respectively (p > 0.05). There was no statistically significant difference between the number of crypts containing Paneth cells in the biliopancreatic and common loops, so the regulatory function of these cells was preserved in any variant of gastric bypass with a single anastomosis. Conclusions. Morphological and morphometric changes in the small intestinal mucosa after gastric bypass with a single anastomosis may be associated with various physiological conditions and have clinical significance for understanding the mechanisms of absorption and intestinal protection. Additional studies with a larger number of samples and the use of modern methods of morphological analysis are needed to deepen the understanding of these processes.