Rectal Hyposensitivity and Altered Anorectal Tone, Capacity and Motor Function in Faecal Incontinence after Surgery for Anal Fissure and Rectal Prolapse

Aim: To investigate the rectal and anal sphincter factors that might contribute to the development of fecal incontinence (FI) after anal fissure and rectal prolapse surgery. Methods: Fourteen patients with FI after sphincterotomy (n = 8) and rectal prolapse surgery (n = 6) were studied [clinical assessment, rectosigmoidoscopy, anorectal manometry, including rectoanal inhibitory reflex (RAIR) measurement, and barostat (rectal sensitivity, tone, compliance and capacity) and compared with 10 asymptomatic healthy subjects (HS). The time after surgery was over 22 months. The continence score was after sphincterotomy 12.8 ± 1 and after rectal prolapse surgery 14.4 ± 2 (St Mark’s FI grading system). Results: Compared with HS, rectal tone was increased in patients who had undergone sphincterotomy (p = 0.042), and rectal capacity lessened after rectal prolapsed procedures (p = 0.037). All patients at similar pressures as HS reported a noxious stimulus of pain. In sphincterotomy patients, the thresholds for non-noxious stimuli of the sensations of gas (p = 0.016) and urge to-defecate (p = 0.043) were reported at higher pressures compared with HS. Patients with sphincterotomy showed greater anal resting pressures (p = 0.014), greater anal squeeze pressure (p = 0.004) and a higher amplitude of relaxation in their RAIR (p = 0.0006) than HS. Patients with rectal prolapse surgery showed lesser percentages of relaxation (p = 0.029). Conclusion: Anorectal surgical procedures alter continence mechanisms in diverse ways. Patients with sphincterotomy present motor alterations, impaired rectal tone and rectal hyposensitivity for non-noxious stimuli. Patients after rectal prolapse surgery present altered rectal capacity and RAIR with lesser percentage of relaxation. The results also suggest that impaired afferent nerve pathways and abnormal rectal structures and functions are involved in the pathogenesis of FI after anal fissure and rectal prolapse surgery.