The role of rectal hyposensitivity in the development of functional hindgut disorders: clinical significance and pathophysiology

Abstract

Background Rectal hyposensitivity (RH) is associated with functional hindgut disorders. It is hypothesized to involve afferent pathway dysfunction. However, little is known regarding its clinical impact. Aims To assess whether RH is: • clinically important and associated with specific symptoms; • secondary to afferent neuronal dysfunction; and • primarily a pelvic abnormality. Methods Epidemiological studies were conducted: (1) a case-controlled study stratified by sensory status, assessing symptoms of constipation and incontinence, health status and quality of life; (2) an observational study exploring RH in faecal incontinence in men; (3) an observational study examining the impact of RH on defaecatory urge. Pathophysiological studies were also conducted: (1) transmission of visceral sensory information was evaluated using rectal evoked potentials;(2) somatic sensory function and visceral efferent function were examined in patients with and without RH. Results RH is associated with constipation. Patients with RH have more severe symptoms and worse health status and quality of life. Constipated patients report altered defaecatory urge compared to controls, most notably in those with RH. RH is associated with concurrent constipation and evacuatory dysfunction in males with incontinence. Patients with RH have delayed evoked potential latencies, without alteration of cortical activation. A proportion have elevated somatic sensory thresholds although efferent function is similar between groups. Conclusions 1. In patients with constipation, those with RH have a worse clinical phenotype, with poorer health status and quality of life. Patients with constipation, (particularly those with RH), have alteration of defaecatory urge. 2. RH and constipation may contribute to incontinence in males where sphincter dysfunction is less important. 3. RH is associated with delayed afferent transmission indicating primary afferent pathway dysfunction. In a proportion, reflecting a possible generalised sensory neuropathy. These studies confirm that intact rectal sensation is fundamental to normal hindgut function. Impaired visceral sensation is thus an important therapeutic target.