Fecal incontinence in systemic sclerosis is secondary to neuropathy

Systemic sclerosis (SSc) is a chronic multi-system autoimmune disorder with gastrointestinal tract (GIT) involvement in up to 90% of patients and anorectal involvement occurs in up to 50% of patients. The pathogenesis of gastrointestinal abnormalities may be both myogenic and neurogenic. We aimed to identify which anorectal physiological abnormalities correlate with clinical symptoms and thus understand the pathophysiology of anorectal involvement in SSc.

In total, 44 SSc patients (24 symptomatic (Sx) (fecal incontinence) and 20 asymptomatic (ASx)) and 20 incontinent controls (ICs) were studied. Patients underwent anorectal manometry, rectal mucosal blood flow (RMBF), rectal compliance (barostat), and rectoanal inhibitory reflex assessment (RAIR).

Anal squeeze pressure was lower in the IC group compared with both the ASx and Sx groups (IC: 46.95 (30-63.9)) vs. ASx: 104.6 (81-128.3) vs. (Sx: 121.4 (101.3-141.6); P < 0.05). Resting pressure was lower in the IC group. RMBF and rectal compliance did not differ between groups. Anal, but not rectal, sensory threshold, was significantly attenuated in Sx patients (Sx: 10.4 (8.8-11.4) vs. ASx: 6.7 (5.7-7.7) vs. IC: 8.5 (6.5-10.4); P < 0.05). There was a positive correlation between anal sensory thresholds and incontinence score in SSc patients (r = 0.54; P < 0.05). RAIR was absent in 11/24 Sx patients but only in 2/20 ASx and in 1/20 IC patients.

Fecal incontinence in SSc is related to neuropathy as suggested by absent RAIR and higher anal sensory threshold and is related less so to sphincter atrophy and rectal fibrosis.