The Study of Anorectal Function Using High-resolution Anorectal Manometry in Patients With Fecal Impaction

This study aims to evaluate anorectal function through high-resolution anorectal manometry (HRAM) in patients with constipation and fecal impaction, considering the limited information available on this subject.

HRAM conducted between January 2021 and November 2023 (785 procedures) were reviewed. Patients were identified as individuals who experienced at least one episode of hard stools in the last year that were unable to evacuate. They were compared with constipated patients without fecal impaction episodes (control group). HRAM was performed using solid-state equipment (Medtronic). Logistic regression analysis was done to identify demographic-clinical factors and manometric variables associated with fecal impaction.

Fecal incontinence was independently associated with fecal impaction [adjusted odds ratio (aOR): 20.4, 95% CI: 2.5-167.8] after adjusting for demographic and clinical variables. Severe rectal hyposensitivity (no perception of urgency from a volume of 200 mL) was present in 38.2% of patients with fecal impaction and 5.9% of controls ( P =0.001). Defecatory dyssynergia was diagnosed in 29.4% of patients with fecal impaction. Lower squeeze pressure and severe rectal hyposensitivity were independently associated with fecal impaction with an aOR of 0.98 (95% CI: 0.98-0.99) and aOR of 10.4 (2-54.1), respectively, and after adjusting for all manometric parameters. Hypotonia and hypo-contractility of the anal canal were found in 53.8% and 46.2% of patients with fecal impaction and incontinence, respectively.

Patients with fecal impaction often show rectal hyposensitivity and anal hypo-contractility, which are independent risk factors for impaction. Fecal incontinence is linked to fecal impaction, and their coexistence is associated with reduced anal canal pressures.