Digestive, Anorectal, and Urogenital Functions in Patients with Type 2 Diabetes Mellitus, Impaired Glucose Tolerance and Normal Glucose Tolerance: Association with Autonomic Neuropathy.

Aims: Gastrointestinal disorders, including constipation and fecal incontinence, are common in type 2 diabetes mellitus (T2DM) and may derive from diabetic autonomic neuropathy, severe intestinal bacterial overgrowth, or a dysfunctional anorectal sphincter. The present study aims to characterize the correlation between these conditions.

Methods: Patients with T2DM, prediabetes, and normal glucose tolerance (NGT) were included. The anorectal function was assessed with high-resolution anorectal manometry. Patients were screened for autonomic neuropathy by measuring olfactory, sweat, and erectile dysfunction as well as heart rate variability. Constipation and fecal (in-)continence were evaluated using validated questionnaires. Breath tests were used to assess severe intestinal bacterial overgrowth.

Results: We included 59 participants (32 (54.2%) with T2DM, 9 (15.3%) with prediabetes, and 18 (30.5%) NGT). The presence of autonomic neuropathy, severe bacterial overgrowth, and symptoms of constipation and incontinence were comparable. HbA_1c was correlated with an increased anorectal resting sphincter pressure (r=0.31, P=0.019) and constipation symptoms (r=0.30, P=0.031). In patients with a long-standing diagnosis of T2DM, significantly higher values for maximum anorectal resting pressure (Δ=+27.81±7.84 mmHg, P=0.0015) and baseline pressure (Δ=20.50±9.74 mmHg, P=0.046) were found compared with NGT, but not with prediabetes.

Conclusions: Long-standing T2DM increases anorectal sphincter activity, and constipation symptoms are associated with higher HbA_1c levels. The lack of an association of symptoms with autonomic neuropathy suggests glucotoxicity as the primary mechanism.