Clinical Characteristics and Pathophysiology of Fecal Incontinence Mixed With Constipation: An Underrecognized Problem

INTRODUCTION: – Fecal incontinence (FI) and chronic constipation (CC) are diagnosed as distinct problems, although many suffer with both problems. The phenotypical features and underlying mechanisms of FI mixed with CC (FI-MC) is unclear. We investigated the clinical and pathophysiological characteristics of FI-MC and compared with FI alone and healthy controls.METHODS: – In a retrospective study, patients with FI were categorized as having FI-MC or FI alone. For comparison, we recruited healthy controls. All subjects completed bowel symptom questionnaire, anorectal manometry, balloon expulsion, neurophysiology, and anal ultrasound tests. Data were compared between the 3 groups.RESULTS: – We evaluated 165 patients with FI-MC, 184 with FI, and 31 controls. The prevalence of excessive straining, incomplete evacuation, pain, bloating, use of digital maneuvers, and enemas were higher (P < 0.001) in the FI-MC than FI group. Anal resting pressure was lower (P < 0.001) in FI than FI-MC group and controls. Anal squeeze and sustained squeeze pressures were lower (P < 0.001), and lumbar and sacral plexus nerve conduction was prolonged (P < 0.001) in the FI-MC and FI groups compared with controls, but similar between patient groups. Dyssynergic defecation was more (P < 0.01) prevalent in FI-MC than FI or controls. Rectal sensory thresholds were lower in the FI-MC group than controls (P < 0.05), but not between patient groups. The FI group had higher (P < 0.01) prevalence of anal sphincter defects than FI-MC.DISCUSSION: – Patients with FI can be categorized into 2 phenotypes as FI alone and FI-MC. Each group demonstrates distinct clinical characteristics and pathophysiology. Recognizing each phenotype may improve management of patients with FI.