RECTAL HYPOSENSITIVITY: CLINICAL AND PHYSIOLOGICAL IMPACT ON PATIENTS WITH CHRONIC CONSTIPATION

Abstract

Intact rectal sensation is integral to normal anorectal function. Rectal hyposensitivity (RH) implies diminished rectal sensory perception and is currently diagnosed using standard anorectal physiology tests. There is currently a lack of understanding regarding the nature and severity of symptoms, and pathophysiological mechasnisms by which RH leads to symptoms of constipation. Symptom severity and physiological abnormalities (potential pathophysiological mechanisms) were studied in patients with RH referred to a tertiary centre for evaluation of their symptom of intractable constipation. A pilot study using a novel technique to study recto-anal and recto-rectal reflexes in health and in patients with RH is also presented. RH was not associated with more severe symptoms as assessed using a standard constipation severity questionnaire. RH is more commonly associated with rectal evacuatory dysfunction (functional type). RH is also associated with a specific pattern of transit delay, where there is more hold up of the isotope in the left colon and this is independent of rectal evacuatory dysfunction. Afferent dysfunction in the majority of patients with rectal hyposensitivity relates purely to visceral pathways. However, a combined viscero-somatic pelvic sensory neuropathy is present in a proportion of patients. Similarly, a combined sensori-motor dysfunction was also seen in a subgroup of patients. Patients with RH have abnormal sampling and rectal contractile response to distension and this may play an important role in the pathophysiology of symptoms. The level of interruption of afferent pathway is likely to be heterogenous in patients with RH and constipation. Patients with RH display distinct physiological abnormalities that may be important to identify to tailor management. Whether, this leads to improved clinical outcomes needs to be further evaluated.