Unilateral pudendal neuropathy is common in patients with fecal incontinence

Pudendal neuropathy and fecal incontinence frequently coexist; however, the contribution of neuropathy is unknown. The pudendal nerve innervates the external anal sphincter muscle, anal canal skin, and coordinates reflex pathways. Lateral dominance or a dominantly innervating nerve and its subsequent damage may have major implications in the etiology and treatment of fecal incontinence. This study was designed to establish the prevalence of pudendal neuropathy, in particular a unilateral one, and to examine the impact on anorectal function.

A total of 923 patients (745 females; mean age, 52 (range, 17-92) years) with fecal incontinence were studied using endoanal ultrasonography, anorectal manometry, rectal sensation, and pudendal nerve terminal motor latencies.

A total of 520 patients (56 percent) demonstrated a pudendal neuropathy, which was unilateral in 38 percent (351 patients; 169 right-sided, 182 left-sided). Neuropathy, whether it was bilateral (bilateral vs. normal; 56 (range, 7-154) cm H2O) vs. 67 (range, 5-215) cm H2O; P < 0.01) or unilateral (unilateral vs. normal; 61 (range, 0-271) cm H2O vs. 67 (range, 5-215) cm H2O; P = 0.04) was associated with reduced anal resting tone. This also was seen with respect to squeeze increments (bilateral vs. normal; 34 (range, 0-207) cm H2O vs. 52 (range, 0-378) cm H2O; P < 0.001, unilateral vs. normal; 41 (range, 0-214) cm H2O vs. 52 (range, 0-378) cm H2O; P < 0.01). In those with intact sphincters, unilateral neuropathy was associated with reduced squeeze increments (unilateral vs. normal; 60 (range, 10-286) cm H2O vs. 69 (range, 7-323) cm H2O; P = 0.01) but no significant reduction in resting pressures. There was no association between pudendal neuropathy and abnormal rectal sensitivity.

Unilateral pudendal neuropathy is a common abnormality in individuals with fecal incontinence and is significantly associated with both attenuated resting pressures and squeeze increments. Although there are limitations in the interpretation of pudendal nerve terminal motor latencies, this study demonstrates that further exploration of the concept of lateral dominance is needed.