THE ROLE OF TRANSIENT INTERNAL SPHINCTER RELAXATION IN FECAL INCONTINENCE

Twenty-five (18%) of 140 incontinent patients and 6 (17%) of 35 normal controls showed episodes of spontaneous internal sphincter relaxation during 30 min multiport manometric and electromyographic recording under resting conditions. The episodes lasted at least 15 s and reduced the pressure in the outermost anal channels by at least 20 cm of water. Patients exhibited more episodes of relaxation than controls (4.3±0.6 vs 2.3±0.2 per subject; mean±SEM; p<0.05) and the pressures fell to lower values (19±1 vs 42±5 cm water, p<0.01), but the duration of relaxation was not significantly different (53±4 vs 40±7 s). Episodes of spontaneous relaxation were associated with simultaneous rectal contractions in 33% of the normal subjects and 45% of incontinent patients. Unlike normal subjects, most of the episodes of transient relaxation recorded in the incontinent group were not associated with compensatory increases in the electrical activity of the external anal sphincter (77% vs 17%; p<0.05). Over 50% of the incontinent patients who showed spontaneous relaxation also showed post squeeze or post-strain IAS relaxations whereas these were seen in less than 6% of the normal subjects with spontaneous relaxation. The rectal volumes, required to elicit anal relaxation (10±0 vs 28±7 ml; p<0.05), to incude sustained relaxation (60±8 vs 82±5 ml; p<0.05), to elicit a sensation of 'wind' (19±3 vs 27±8 ml; p<0.05) and to cause a desire to defaecate (36±4 vs 63±9 ml; p<0.05) were all lower in the incontinent patients who showed spontaneous relaxations than in the incontinent control group. In conclusion, spontaneous relaxation of the internal sphincter may be an important factor leading to faecal incontinence in patients with a sensitive rectum, especially as they tend to occur in these subjects in the absence of a compensatory increase in external sphincter activity. © 1990 Springer-Verlag.