Original Contribution
The American Journal of Gastroenterology (2005) 100, 106–114; doi:10.1111/j.1572-0241.2005.40021.x
Rectal Hyposensitivity: A Disorder of the Rectal Wall or the Afferent Pathway? An Assessment Using the Barostat
This work was presented in part at the 19th International Symposium on Gastrointestinal Motility, Barcelona, Spain, October 2003, and appears in abstract form in Neurogastroenterol Motil 2003;15:82.
Marc A Gladman MRCOG, MRCS (Eng), Lee S Dvorkin MRCS (Eng), Peter J Lunniss MS, FRCS, Norman S Williams MS, FRCS and S Mark Scott PhD
Centre for Academic Surgery (Gastrointestinal Physiology Unit), Barts and The London, Queen Mary's School of Medicine & Dentistry, Whitechapel, London E1 1BB, United Kingdom
Correspondence: Dr S Mark Scott, PhD, Senior Clinical Scientist, Gastrointestinal Physiology Unit, 3rd Floor Alexandra Wing, The Royal London Hospital, Whitechapel, London E1 1BB, UK.
Received 26 July 2004; Accepted 7 September 2004.
Abstract
OBJECTIVE:
Rectal hyposensitivity (RH) relates to a diminished perception of rectal distension. Diagnosis on the basis of abnormal threshold volumes on balloon distension alone may be inaccurate due to the influence of differing rectal wall properties. The aim of this study was to investigate whether RH was actually due to impaired afferent nerve function or whether it could be secondary to abnormalities of the rectal wall.
METHODS:
A total of 50 patients were referred consecutively to a tertiary referral unit for physiologic assessment of constipation (Rome II criteria), 25 of whom had associated fecal incontinence. Thirty patients had RH (elevated threshold volumes on latex balloon distension), and 20 patients had normal rectal sensation (NS). Results were compared with those obtained in 20 healthy volunteers (HV). All subjects underwent standard anorectal physiologic investigation, and assessment of rectal compliance, adaptive response to isobaric distension at urge threshold, and postprandial rectal response, using an electromechanical barostat.
RESULTS:
Mean rectal compliance was significantly elevated in patients with RH compared to NS and HV (p < 0.001). However, 16 patients with RH (53%) had normal compliance. Intensity of the urge to defecate during random phasic isobaric distensions was significantly reduced in patients with RH compared to NS and HV (p < 0.001). The adaptive response at urge threshold was reduced in patients with RH compared to NS and HV (p < 0.001), although spontaneous adaptation at operating pressure was similar in all three groups studied (p= 0.3). Postprandially, responses were similar between groups.
CONCLUSION:
In patients found to have RH on simple balloon distension, impaired perception of rectal distension may be partly explained in one subgroup by abnormal rectal compliance. However, a second subgroup exists with normal rectal wall properties, suggestive of a true impairment of the afferent pathway. The barostat has an important role in the identification of these subgroups of patients.
