Rectal Compliance in Patients with Functional Constipation and Constipation-predominant Irritable Bowel Syndrome

Background:Rectal compliance is considered an important feature of rectal motor function,and may be one of the main pathophysiologic factors in the pathogenesis of constipation.Aims:To investigate the differences in the rectal sensation and rectal compliance in patients with different subtypes of constipation,and to understand the clinical significance of rectal compliance.Methods:Using a computerized barostat with a 500 ml polyethylene balloon,the visceral sensation and compliance in the rectum were determined in patients with functional constipation(FC),constipation-predominant irritable bowel syndrome(C-IBS)and normal controls.The pressure was controlled by rapid phasic distention.Results:The rectal compliance was significantly decreased in FC and C-IBS patients than that in the normal controls(6.34 ml/mm Hg±2.26 ml/mm Hg and 6.50 ml/mm Hg±2.48 ml/mm Hg vs.9.57 ml/mm Hg±2.77 ml/mm Hg,P0.05),but no difference was found between that in FC and C-IBS patients.The rectal compliance was significantly increased in patients with rectal hypersensitivity,however,the relationship between rectal sensation and rectal compliance in FC and C-IBS patients were not consistent.Conclusions:Impaired perception of rectal distension may be partially explained by abnormal rectal compliance in some constipation patients.Basing on the changes of rectal compliance and rectal sensation,one may be able to differentiate the different subtypes of constipation.