Impaired anal sensation and early diabetic faecal incontinence

Faecal incontinence develops in up to 20% of diabetic patients. To try to determine the relative contributions of sensory and motor neuropathy in this troublesome complication, anorectal function was examined in 10 male diabetic patients with early faecal incontinence (mucus leakage or faecal staining without the need to wear a pad), 10 asymptomatic male diabetic patients, and 10 normal control subjects. Motor function was tested using anal manometry to determine the resting and maximum squeeze pressure, and the functional anal canal length. No significant differences were found between the groups. Sensory function was tested by measuring the mucosal sensitivity to electrical stimulation, and the response to inflation of a balloon in the rectum. In the mid-anal canal position the symptomatic patients had a significantly higher sensory threshold at 6.6 +/- 2.8 mA compared with 3.0 +/- 1.2 mA in the normal control subjects (p less than 0.002), and in the high anal zone symptomatic patients had a significantly elevated sensory threshold at 9.1 +/- 2.0 mA compared with 4.6 +/- 1.6 mA in asymptomatic patients and 3.6 +/- 1.3 mA in the normal control subjects (both p less than 0.001). There were no significant differences in the first sensation of fullness, maximum tolerated volume or percentage fall from resting pressure between the groups on inflation of the balloon. Elevation of the sensory threshold in the upper anal canal is an early abnormality in the development of diabetic faecal incontinence.