The Recto-Anal Inhibitory Reflex (RAIR): abnormal response in diabetics suggests an intrinsic neuro-enteropathy

Abstract

INTRODUCTION: The recto-anal inhibitory reflex (RAIR) is characterized by reflex relaxation of the anal canal in response to electrical stimulation of the rectal mucosa, and is mediated by nitrergic neural plexuses within the gut wall. Impairment of this reflex may lead to incontinence. AIM: To measure anal canal pressures, anal mucosal electrosensation and RAIR in diabetic patients and correlate these measurements with incontinence for gas or faeces. METHODS: Anal canal pressure, RAIR and continence was evaluated in 30 diabetic patients [Male:Female=13:17, median age 57 years (range 37- 70)], and these data were compared with similar data obatained from 22 age and sex matched 'healthy' controls [Male:Female= 9:13, median age 51 years (range 19 - 65 )]. Median duration of diabetes was 8 years (range 3 -30 ). 12 (40%) of the 30 diabetics had impaired continence for gas (n=12) and liquid faeces (n=3). None ofthe controls had incontinence. RESULTS: Maximum resting anal canal pressure (MRP) was [median (range)]: Patients 30mmHg (20-75) vs. Controls 40mmHg (20-105), P=0.61. Maximum squeeze pressure (MSP) [median (range)]: Patients 65mmHg (30- 150) vs. Controls 84mmHg (35-230), P=0.59. Threshold rectal mucosal eletrosensation (RMES-T) [median (range)]: Patients 27 mA (5-40) vs. Controls l3mA (5-28), P=0.03. Maximum tolerable rectal mucosal electrosensation [median (range)]: Patients 40 mA (20-60) vs. Controls 20 mA (10-30), P=0.042 (all comparisons using Wilcoxon rank test). RAIR was present in 8, abnormal in 5 (1 with incontinence), and absent in 17 (II with incontinence) diabetics while it was present in 18 and abnormal in 4 controls (test of proportion, P=0.03 I). CONCLUSIONS: RAIR was impaired in significantly more patients with diabetes than controls implying impairment of intrinsic neuronal function. All diabetic patients with incontinence had impaired or absent RAIR. Impairment of this reflex may be a useful predictor of incontinence in diabetics.