Acute hyperglycaemia affects anorectal motor and sensory function in normal subjects

Background-The pathogenesis of anorectal dysfunction, which occurs frequently in patients with diabetes mellitus, is poorly defined. Recent studies indicate that changes in the blood glucose concentration have a major reversible effect on gastrointestinal motor function. Aims-To determine the effects of physiological changes in blood glucose and hyperglycaemia on anorectal motor and sensory function in normal subjects. Subjects-In eight normal subjects measurements of anorectal motility and sensation were performed on separate days while blood glucose concentrations were stabilised at 4, 8, and 12 mmol/l. Methods-Anorectal motor and sensory function was measured using a sleeve/sidehole catheter incorporating a balloon, and electromyography. Results-The number of spontaneous anal relaxations was greater at 12 mmol/l than at 8 and 4 mmol/l glucose (p<0.05 for both). Anal squeeze pressures were less at a blood glucose of 12 mmol/l when compared with 8 and 4 mmol/l (p<0.05 for both). During rectal distension, residual anal pressures were not significantly different between the three blood glucose concentrations. Rectal compliance was greater (p<0.05) at a blood glucose of 12 mmol/l when compared with 4 mmol/l. The threshold volume for initial perception of rectal distension was less at 12 mmol/l when compared with 4 mmol/l (40 (20-100) ml versus 10 (10-150) ml, p<0.05). Conclusions-An acute elevation of blood glucose to 12 mmol/l inhibits internal and external anal sphincter function and increases rectal sensitivity in normal subjects. In contrast, physiological changes in blood glucose do not have a significant effect on anorectal motor and sensory function.