Differences in the pressures of canal anal and rectal sensitivity in patients with fecal incontinence, chronic constipation and healthy subjects

Introduction: There exist a great variability in the manometric findings between patients with anal incontinence (AI) and healthy subjects. The correlation between the pressures of the anal canal and the AI is not exact by the wide rank of normal values. Objectives: Prospective study to evaluate differences in the pressures of the anal canal and in rectal sensitivity in patients with AI, chronic constipation (CC) and healthy subjects. Material and methods: Ninety four patients with AI, 36 patients with CC and 15 healthy subjects were included. The following data were obtained: age, sex, resting pressure, anal canal length (ACL), squeeze maximum pressure (SMP)., squeeze pressure duration (SPD), first sensation, urge and maximum tolerated volume (MTV). Statistical study: test of Kruskal-Wallis, test of Mann-Whitney, and multinomial logistic regression test. Results: There were significant differences in the resting pressure (p < 0.001), the ACL (p < 0.001) and the SMP (p < 0.01) in the group of AI with respect to the other two groups. The volume for the first sensation was significantly lower in the healthy subjects than that in the other two groups (p < 0.05). The urge volume and the MVT were smaller in the group with AI with respect to the other groups (p < 0.001). In multivariate analysis the age, the resting pressure and the volume for the first sensation and urge increase the relative risk for AI. Conclusions: The greater age, the decrease in anal canal resting pressure and the alteration of rectal sensation increase the risk for AI.