Altered serotonin immunoreactivities in the left colon of patients with colonic inertia

BACKGROUND: Serotonin is an important positive regulator of colonic motility and transit. Its quantity and distribution in the left colon could be abnormal in patients with colonic inertia (CI) and contribute to the disease. AIM: To evaluate serotonin positive cells and immuno-reactivities in the mucosa, submucosa and muscularis propria of the left colon from patients with CI was compared to a control group. PATIENTS AND METHODS: Nineteen patients who underwent subtotal colecotomy for CI were assessed. The control group consisted of 15 patients who underwent left hemicolectomy for colonic cancer; histologically normal tissue specimens were used. Immunohistochemical staining for serotonin was performed. In the mucosa, the average number of serotonin positive cells per microscopic field (200 x ) was determined. The positively stained area (square pixels) in the mucosa, submucosa and muscularis propria per microscopic field (200 x ) was calculated utilizing a computer image analysis program. RESULTS: In the mucosa, both the number of serotonin positive cells and positively stained area were significantly higher in the patient group than in controls (P < 0.05). The difference in serotonin positive area in the submucosa in the CI group compared to the control group was not statistically significant. There was a very significant correlation between the serotonin positive area in the submucosa and muscularis propria in controls (r=0.65, p < 0.01), but not in patients with CI. CONCLUSION: The increased serotonin level in patients with CI may contribute to the disease or be an adaptive response to some other pathology. The lack of a positive correlation in serotonin levels between the submucosa and muscularis propria in CI patients suggests that the coordinated distribution of serotonin may be disrupted in CI.