Altered Colorectal Compliance and Anorectal Physiology in Upper and Lower Motor Neurone Spinal Injury May Explain Bowel Symptom Pattern.

Abstract

Supraconal spinal cord injury (SCI) and lower motor neurone spinal cord injury (LMN-SCI) cause bowel dysfunction; colorectal compliance may further define its pathophysiology. The aim of this study was to investigate rectal (RC) and sigmoid (SC) compliance and anorectal physiology parameters, in these subjects. Twenty-four SCI subjects with gut symptoms (14 RC, 10 SC) and 13 LMN-SCI subjects (9 RC, 4 SC) were compared with 20 spinal intact controls (10 RC, 10 SC). Staircase distensions were performed using a barostat. Anorectal manometry, including rectoanal inhibitory reflex (RAIR) measurement, was performed in all. Data presented as mean±standard error (SCI/LMN-SCI vs. controls). SCI subjects had a higher RC (17.0±1.9 vs. 10.7±0.5 ml/mm Hg, P<0.05) and SC (8.5±0.6 vs. 5.2±0.5 ml/mm Hg, P=0.002). LMN-SCI subjects had a lower RC (7.3±0.7 ml/mm Hg, P=0.0021) while SC was unchanged (8.3±2.2 ml/mm Hg, P>0.05). Anal resting pressure was decreased in SCI (55±5 vs. 79±7 cmH2O, P=0.0102). Anal squeeze pressure was decreased in LMN-SCI (76±13 vs. 154±21 cmH2O, P=0.0158). In SCI and LMN-SCI, the amplitude reduction of the RAIR was greater (62±4% and 70±6% vs. 44±3%, P=0.0007). Colorectal compliance abnormalities may explain gut symptoms: increased RC and SC contributing to constipation in SCI, reduced rectal compliance contributing to fecal incontinence (FI) in LMN-SCI. Reduced resting anal pressure in SCI and reduced anal squeeze pressure in LMN-SCI along with a greater RAIR amplitude reduction may be factors in FI. These co-existing abnormalities may explain symptom overlap, and represent future therapeutic targets to ameliorate neurogenic bowel dysfunction.