Observations on some motility disturbances of the human distal bowel and pelvic floor

Abstract

The following paragraphs summarise the principal findings and conclusions drawn from results of the studies described in the previous Sections. | 1. The use of a microtransducer in anorectal manometry avoids many of the drawbacks of conventional fluid-filled systems. The data obtained is highly reproducible and probably more accurate. | 2. The proctometrogram provides a reproducible and useful method of evaluating the pressure-volume distension characteristics of the rectum in health and disease. The expected correlation between compliance and volume is confirmed. There do not appear to be significant variations in rectal volume or compliance with age in healthy subjects. | 3. The electrophysiological latency of the pudendo-anal reflex in health is 38.5±5.8 ras ( Mean±SD, n=38 ). It is completely reproducible and does not appear to vary with age or sex. | 4. In symptomatic chronic radiation anorectal injury: | 4.1 The manometric function of the internal anal sphincter is compromised with diminution in sphincter length, basal pressure and abnormalities of the rectosphincteric reflex. | 4.2 The external anal sphincter remains manoraetrically normal. Its mean motor unit potential duration is increased although the latency of the pudendo-anal reflex is unaffected. These findings suggest possible minor damage to its terminal innervation. | 4.3 The volume and compliance of the rectum are severely diminished, there being a significant positive correlation between these parameters. The manometric changes correlate well with symptomatic and sigmoidoscopic findings. | 5. Following colo-anal sleeve anastomosis for severe chronic radiation injury to the rectum the organic complications are resolved but some of the functional abnormalities persist. These are in part due to: | 5.1 Persisting internal anal sphincter dysfunction. | 5.2 External anal sphincter dysfunction on rectal distension and defaecation straining. | 5.3 Persisting severe reduction in rectal volume and compliance. | 5.4 Reduction in rectal sensory threshold volume, although rectal 'proprioception' remains intact. | 6. Some of the sphincteric and rectal manoraetric and symptomatic disturbances in chronic radiation injury and those following colo-anal sleeve anastomosis may be secondary to damage to the myenteric plexus which is histologically demonstrable. | 7. Following complete transection of the spinal cord above the sacral segments, severe constipation may result. The differential effects on colorectal and pelvic floor motility of sacral anterior root stimulators in five such patients may be summarised as follows: | 7.1 There is an increasing influence on striated pelvic floor muscle activity from S2 to S4. | 7.2 S2 stimulation results in occasional low pressure phasic colorectal contractions. | 7.3 S3 stimulation results in high-pressure phasic colorectal contractions reminiscent of peristaltic activity. This response is frequency dependent. | 7.4 S4 stimulation results in tonic pressure increases in the colon and rectum. These may simply be the cosequence of increase in intra-abdominal pressure due to pelvic floor contraction. | 8. Two groups of elderly patients who suffer from chronic constipation are identifiable as defined by the proctometrogram. One group has a significantly increased rectal capacity and compliance - a 'megarectum' syndrome. The second group shows significant reduction in rectal volume and compliance demonstrating hypertonicity of the distal bowel, both groups have blunting of rectal sensation to distension. Increased gastrointestinal transit times seem mainly due to rectal stasis. Abnormalities of the pudendo-anal reflex suggest that neurogenic deficits of the sacral spinal cord may contribute to these disturbances of colorectal function. | 9. Electrophysiological studies in young women with chronic idiopathic constipation suggest the possibility of a neurogenic deficit in the conus medullaris in the presence of normal sphincteric innervation. | 10. In neurogenic faecal incontinence the latency of the pudendo-anal reflex is significantly prolonged and its amplitude diminished. It may be absent in some patients. A significant correlation exists between the latency of the reflex and the corresponding mean motor unit potential duration of the external anal sphincter. These findings confirm the its usefulness as an index of neuropathy in neurogenic faecal incontinence. | 11. In genuine female stress urinary incontinence the latency of the pudendo-anal reflex is significantly prolonged, as are the latencies of two other polysynaptic sacral reflexes ( dorsal nerve to urethral sphincter, urethral mucosa to external anal sphincter ). The electrosensitivity of both the dorsal nerve and urethral mucasa is significantly blunted. These observations point to a strong neurogenic element in this disorder. The clinical and manometric response to pelvic floor physiotherapy is disappointing.