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Biomedical subjects

W M Sun

Publications and source records attributed to W M Sun.

At least 19 recordsLinked to original sources
PubMed1992

Haemorrhoids are associated not with hypertrophy of the internal anal sphincter, but with hypertension of the anal cushions.

A combined manometric and ultrasonographic study of the internal anal sphincter was carried out in 20 patients with haemorrhoids and 20 age-matched normal controls. Mean(s.e.m.) basal anal pressure was significantly higher in patients than in controls, 62(4) versus 45(6) cmH2O (P less than 0.05), although there were no significant differences in mean maximum basal and squeeze pressures. During rectal distension 90 per cent of patients showed no reduction in anal pressure in the outermost anal channel, although the internal sphincter electromyogram was suppressed and the external sphincter electromyogram did not necessarily increase above baseline. The mean(s.e.m.) maximum residual pressure was significantly higher in patients, 70(6) versus 45(6) cmH2O (P less than 0.05). Direct pressure measurement in anal cushions exhibited abnormally high median pressure in patients compared with controls, 35 versus 10 cmH2O (P less than 0.001). Pressures recorded during coughing and straining were also significantly higher in patients than in controls (P less than 0.001). Ultrasonographic study of the anal canal revealed a clear image of the internal sphincter, the thickness of which could easily be measured. The mean(s.e.m.) thickness of the sphincter was not significantly different, 2.3(0.2) versus 2.1(0.1) mm, between patients with haemorrhoids and controls (P = 0.18). The absence of any significant differences in the internal sphincter thickness between normal subjects and patients with haemorrhoids suggests that the high anal pressure in patients with haemorrhoids is of vascular origin.

Adult↗
PubMed1992

Anorectal function in patients with complete supraconal spinal cord lesions.

Anorectal manometry and sphincter electromyography were performed in 23 patients with complete supraconal traumatic spinal injuries and 30 age and sex matched control subjects. Basal pressures in the spinal group were similar to those in normal subjects but conscious control of sphincter activity was abolished in all spinal patients. Discriminant rectal sensation was also abolished during rectal distension, but 40% of patients experienced a dull pelvic ache at maximum levels of distension. Phasic rectal contraction and anal relaxation were present but exaggerated and induced at lower distending volumes than in normal subjects. The configuration of the rectal pressure/volume relationship was linear in patients compared with a reversed 'S' shape in normal subjects. The external anal sphincter response to rectal distension was noticeably attenuated, reinforcing the view that this spinal reflex is heavily modulated by supraspinal centres under normal circumstances. The external anal sphincter response to increases in abdominal pressure was also attenuated, and the anal pressures were strongly correlated with the level of the lesion and the abdominal pressure the patient could generate. No spinal patient showed a decrease in external anal sphincter activity during straining 'as if to defecate.' The exaggerated anorectal smooth muscle responses to rectal distension and the attenuated external sphincter response explain why patients with complete supraconal spinal lesions experience uncontrollable reflex defecation, while the persistance of external and sphincter contraction and the absence of any external anal sphincter relaxation during straining 'as if to defecate' might explain the difficulty that these patients have in consciously expelling rectal contents.

Adolescent↗
PubMed1992

Utility of a combined test of anorectal manometry, electromyography, and sensation in determining the mechanism of 'idiopathic' faecal incontinence.

Combined tests of anorectal manometry, sphincter electromyography and rectal sensation were carried out in 302 patients with faecal incontinence (235 women, 67 men). The results obtained were compared with 65 normal subjects (35 women, 30 men). A mechanism for incontinence was identified in all and the majority of patients had more than one abnormality. Two hundred and seventy eight patients (92%) had a weak external anal sphincter, 185 of these (67%, mostly women) also showed abnormal perineal descent, and 14 women showed clinical evidence of sphincter damage as a result of obstetric trauma. Ten per cent of patients with impaired external anal sphincter contraction showed associated evidence of spinal disease (impaired rectal sensation plus attenuated or enhanced reflex external anal sphincter activity). Unlike the other groups, the 'spinal' group contained equal numbers of men and women. Ninety seven patients (32%) had evidence of a weak internal anal sphincter. The external sphincter was also very weak and 92% of these patients also had perineal descent. Eighty two patients (27%) showed an unstable internal sphincter, characterised by prolonged 'spontaneous' anal relaxation under resting conditions and an abnormal reduction in anal pressure after conscious contraction of the sphincter or an increase in intraabdominal pressure. One hundred and forty two patients (47%) had a hypersensitive rectum associated with enhanced anorectal responses to rectal distension. All these patients had an abnormally weak external sphincter, suggesting that the hypersensitive or 'irritable' rectum should not be regarded as a cause of faecal incontinence unless accompanied by external sphincter weakness. Twenty four patients (8%) showed a normal basal and squeeze pressures and impaired rectal sensation; six showed giant rectal contractions during rectal distension. The results show that idiopathic faecal incontinence is not caused by a single abnormality, and it is suggested that combined anorectal manometry, electromyography, and sensory testing is a useful technique to identify the causes of faecal incontinence and provide a basis for appropriate treatment.

Adolescent↗
PubMed1991

Reflex anal dilatation: effect of parting the buttocks on anal function in normal subjects and patients with anorectal and spinal disease.

Anal dilatation in response to gentle parting of the buttocks has been advocated as a sign of sexual abuse in children, but nothing is known of the physiology of this response or its existence in normal subjects, in patients with spinal disease, and in patients with a weak sphincter and whether it can be elicited after training. To answer these questions we investigated the effect of parting the buttocks on anal function. Combined anal manometry and electromyography was conducted in six normal subjects (five men, one woman, aged 19-53 years), in 18 patients with faecal incontinence (three men, 15 women, aged 30-80 years), and in seven paraplegic patients (six men, one woman, aged 25-36 years), in four of whom the posterior sacral roots had been cut. Parting the buttocks in normal subjects reduced the pressure in the anal canal from 102 (20) to 14 (3) cm H2O (mean (SEM), p less than 0.00001), but did not cause the anus to gape. This drop in pressure was associated with increased electrical activity in the external anal sphincter. Normal subjects could consciously relax the external anal sphincter and reduce the anal pressure but not so as to result in anal gaping during traction on the buttocks, even after anal dilatation. Stimulation of the anal lining by moving a probe in and out of the anal canal increased the activity of the external anal sphincter, raising anal pressures. Paraplegic patients who had lost conscious control of their external sphincters showed anal gaping when the buttocks were parted. A similar phenomenon was seen in patients with faecal incontinence who had weakness of the external anal sphincter, while incontinent patients with weakness of both sphincters showed anal gaping even at rest. Inasmuch as the results of our study can be applied to children, the data suggest that reflex anal dilatation should only be used to support a diagnosis of sexual abuse if sphincter function is otherwise normal and there is no evidence of cerebrospinal disease. Although our results do not support the notion that children could become so conditioned to repeated digital or penile penetration of the anus that they can cause the anus to gape when the buttocks are parted, neither do they exclude it.

Adult↗
PubMed1990

Control of defecation in patients with spinal injuries by stimulation of sacral anterior nerve roots.

OBJECTIVE: To observe the effects of stimulation of the sacral anterior roots on anorectal and low colonic pressures and to programme implanted stimulators to produce defecation. DESIGN: Prospective study of 12 consecutive patients. SETTING: Spinal injuries unit and university gastrointestinal physiology department. PATIENTS: 12 Patients with complete supraconal spinal cord lesions. Their injuries had been sustained at least two years before the study. INTERVENTIONS: A Brindley-Finetech intradural sacral anterior root stimulator was implanted in all patients. Three months postoperatively the stimulator settings were adjusted after measurement of simultaneous anorectal and low colonic pressures. MAIN OUTCOME MEASURES: Full defecation. RESULTS: Six patients achieved complete rectal evacuation of faeces using the implant and subsequently did not require manual help for defecation. For all but one of the patients the total time taken to complete defecation was reduced, and all were free from constipation, the most prevalent gastrointestinal symptom in patients with spinal injuries. CONCLUSIONS: Sacral anterior root stimulators can be programmed to achieve complete unassisted defecation and can considerably improve the quality of life of patients with spinal injuries.

Adult↗
PubMed1990

Hypertensive anal cushions as a cause of the high anal canal pressures in patients with haemorrhoids.

Anorectal manometry and electrophysiology studies were conducted in 25 men with non-prolapsing haemorrhoids, ten men with prolapsing haemorrhoids, and 20 age-matched normal men. Mean(s.e.m.) minimum basal pressures were significantly higher in patients with non-prolapsing haemorrhoids than in normals (61(5) versus 43(7) cmH2O; P less than 0.05) or patients with prolapsing haemorrhoids (55(4) cmH2O; P less than 0.05). There were no significant differences in maximum basal pressures and maximum squeeze pressures. During rectal distension, all normal subjects showed relaxation in all anal channels. However, 92 per cent of patients with non-prolapsing haemorrhoids and 40 per cent of patients with prolapsing haemorrhoids showed no relaxation in the outer anal channels, even when relaxation occurred in the inner anal channels; internal sphincter electrical slow waves were suppressed and the integrated electrical activity of the external sphincter had returned to predistension values. Maximum residual anal pressures during balloon distension were significantly higher in patients with non-prolapsing haemorrhoids than normals (75(7) versus 45(7) cmH2O; P less than 0.01), or patients with prolapsing haemorrhoids (53(3) cmH2O; P less than 0.05). When subjects increased intra-abdominal pressure rectal pressure was significantly higher in patients with non-prolapsing haemorrhoids than in normal subjects (157(10) versus 105(15) cmH2O; P less than 0.05), but not in patients with prolapsing haemorrhoids (126(14) cmH2O). Resting anal cushion pressures in patients with non-prolapsing or prolapsing haemorrhoids were much higher than normal capillary or venous pressure and significantly higher than those recorded in normals (median 35, 35 versus 10 cmH2O; P less than 0.0001). Pressures recorded during coughing (60, 60 versus 30 cmH2O) and straining (78, 80 versus 55 cmH2O) were also significantly higher (P less than 0.0001) in patients than in normals. Pressures after straining were higher than those recorded before (38 versus 29 cmH2O; P less than 0.05) in 60 per cent of patients but no normal subjects and took 18-36 s to return to baseline. This study suggests that the abnormally high pressures in the anal canal in patients with haemorrhoids may be related to an increased vascular pressure in the anal cushions.

Action Potentials↗
PubMed1990

The role of transient internal sphincter relaxation in faecal 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 less than 0.05) and the pressures fell to lower values (19 +/- 1 vs 42 +/- 5 cm water, p less than 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 less than 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.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Effect of oral nicardipine on anorectal function in normal human volunteers and patients with irritable bowel syndrome.

Paired controlled studies were performed in 10 normal volunteers and 32 patients with irritable bowel syndrome to investigate the effect of the calcium channel blocker nicardipine, on the responses of the anorectum to rectal distension and a meal. Nicardipine was administered orally in standard (20 mg) and sustained-release (30 mg twice a day) formulations. In normal volunteers standard nicardipine had no significant effect on the rectal responses to distension but did significantly reduce the postprandial motility index (P less than 0.05). In the patients with irritable bowel syndrome, standard nicardipine caused a significant reduction in distension-induced rectal motor activity (P less than 0.05) and increased the rectal sensory thresholds for desire to defecate and discomfort (P less than 0.02). Slow-release nicardipine caused a significant reduction in distension-induced activity (P less than 0.05) but did not alter rectal sensory thresholds. Both formulations of nicardipine significantly reduced the postprandial motility index (P less than 0.05) and symptoms (P less than 0.05). In conclusion, this study confirms that calcium channel blockers may be useful in the management of irritable bowel syndrome.

Administration, Oral↗
PubMed1990

Sensory and motor responses to rectal distention vary according to rate and pattern of balloon inflation.

Anorectal motor activity and rectal sensation were recorded in 12 normal male subjects during ramp distention of the rectum with water and air at randomized rates of 10, 20, 50, and 100 mL/min and during intermittent rapid distention with air. There were no significant differences between the results of ramp inflation with water or with air, and the repeated infusion of the same medium yielded reproducible results. Ramp distention induced sigmoid pressure-volume profiles. Different sensations occurred at specific points on the pressure-volume curve and were maintained until succeeded by the next sensation. Initial perception of the distention occurred during the initial steep pressure increase, the sensation of wind occurred during the plateau phase, and the desire to defecate occurred at the onset of the final rapid ascent. Rectal sensations were induced at lower volumes at low infusion rates when the slope of the pressure-volume relationship was shallower than at high infusion rates. This suggests that the receptor triggering rectal sensation is not a simple volume or pressure receptor, but is more likely to be a slowly adapting mechanoreceptor lying parallel to the circular muscle of the rectal wall. During rapid intermittent distention, the rectal volumes required to elicit rectal sensations were lower than during ramp distention, although the pressure-volume curve was steeper. Moreover, sensations often only lasted a short period of time but recurred on deflation. These data suggest activation of an additional population of rapidly adapting or high threshold mechanoreceptors. Anal relaxation was always evoked by intermittent rectal distention and was almost always associated with a rectal sensation and an increase in external anal sphincter activity. In contrast, anal relaxation could be absent or delayed during ramp inflation, especially at lower infusion rates, suggesting that internal sphincter can maintain continence for a long period of time while the rectum is slowly filling. Rectal sensation and concomitant external anal sphincter activity was not associated with anal relaxation during ramp inflation; most subjects felt the sensation long after the pressure reached its lowest level. However, under all circumstances the onset of rectal sensation was associated with an increase of external anal sphincter electrical activity. In conclusion, the rectal sensory and anorectal motor responses to distention depend on the rate and pattern of distention, which may activate a different population of receptors. Results from different laboratories cannot be compared directly unless the pattern and rate of distension are the same.

Adult↗
PubMed1990

Anorectal function in incontinent patients with cerebrospinal disease.

Anorectal manometry and the electrical activity of the external anal sphincter were measured in 20 patients with well-defined, incomplete spinal lesions who were referred because of fecal incontinence and in 30 normal subjects. Six patients had a high spinal lesion, 11 had a low spinal lesion, and 3 had mixed high and low spinal lesions. Patients with high spinal lesions had normal basal pressures but abnormally low squeeze pressures and impaired rectal sensation. Unlike normal subjects, there was no relationship between the depth of sphincter relaxation and the distention volumes. The external sphincter responses to rectal distention and increases in intraabdominal pressure were enhanced, and leakage of perfusion fluid was uncommon. Patients with low spinal lesions had abnormally low basal and squeeze pressures, blunted rectal sensation, and showed impaired external anal sphincter responses to rectal distention or increases in intraabdominal pressures. Most of these patients leaked the infused fluid during these maneuvers. Sphincter function in patients with mixed lesions was more severely impaired than in patients with low and high spinal lesions. Patients with mixed lesions showed abnormally low basal and squeeze pressures, impaired rectal sensation, and no external anal sphincter responses to either rectal distention or increases in intraabdominal pressure. Leakage occurred during these maneuvers in all patients with mixed lesions.

Adult↗
PubMed1990

Relation between rectal sensation and anal function in normal subjects and patients with faecal incontinence.

The relation between sensory perception of rapid balloon distension of the rectum and the motor responses of the rectum and external and internal anal sphincters in 27 normal subjects and 16 patients with faecal incontinence who had impaired rectal sensation but normal sphincter pressures was studied. In both patients and normal subjects, the onset and duration of rectal sensation correlated closely with the external anal sphincter electrical activity (r = 0.8, p less than 0.0001) and with rectal contraction (r = 0.51, p less than 0.001), but not with internal sphincter relaxation. All normal subjects perceived a rectal sensation within one second of rapid inflation of a rectal balloon with volumes of 20 ml or less air. Six patients did not perceive any rectal sensation until 60 ml had been introduced, while in the remaining nine patients the sensation was delayed by at least two seconds. Internal sphincter relaxation occurred before the sensation was perceived in three of 27 normal subjects and 11 of 16 patients (p less than 0.001), and could be associated with anal leakage, which stopped as soon as sensation was perceived. The lowest rectal volumes required to induce anal relaxation, to cause sustained relaxation, or to elicit sensations of a desire to defecate or pain were similar in patients and normal subjects. In conclusion, these results show the close association between rectal sensation and external anal sphincter contraction, and show that faecal incontinence may occur as a result of delayed or absent external anal sphincter contraction when the internal anal sphincter is relaxed.

Adult↗
PubMed1989

A common pathophysiology for full thickness rectal prolapse, anterior mucosal prolapse and solitary rectal ulcer.

Anorectal pressures at rest, during conscious contraction of the external sphincter, during serial distension of the rectum and during straining to inflate a balloon were measured in 56 patients (21 patients with full thickness rectal prolapse, 24 patients with anterior mucosal prolapse, 11 patients with solitary rectal ulcer) and in 30 normal subjects. Both basal and squeeze pressures were significantly lower in the three groups of patients compared with matched normal controls (P less than 0.05). During increases in intra-abdominal pressure, anal pressure remained above maximum rectal pressure (P less than 0.05) in normal controls, with the highest anal pressures being recorded in the most caudal anal channels. In contrast, anal pressures tended to be lower than rectal pressures during this manoeuvre in patients with rectal prolapse, anterior mucosal prolapse and solitary rectal ulcer, and the highest pressures were recorded in the channels nearest the rectum. During serial distension of the rectum, 64 per cent of patients with solitary rectal ulcer, 75 per cent with anterior mucosal prolapse and 76 per cent with rectal prolapse, but only 10 per cent of controls, showed repetitive rectal contractions. The highest anal pressure always remained higher than rectal pressure during rectal distension in normal subjects (P less than 0.05) but not in patients. The threshold rectal volume required to cause a desire to defaecate and the maximum tolerable volume were significantly lower (P less than 0.05) in each of the patient groups, compared with normal subjects. The similarity in the results from patients with rectal prolapse, anterior mucosal prolapse and solitary rectal ulcer support the hypothesis that they share a common pathophysiology. In each of the groups, the rectum is hypersensitive and hyper-reactive, and weakness of the anal sphincter creates the conditions for prolapse of the rectum to occur into or through the anal canal.

Adult↗
PubMed1989

External and internal anal sphincter responses to rectal distension in normal subjects and in patients with idiopathic faecal incontinence.

The responses of the external anal sphincter and the internal anal sphincter to rectal distension were studied in 18 female patients who had idiopathic faecal incontinence with perineal descent and 11 female control subjects, by measuring pressures at six sites within the anal canal and the electrical activity of the external sphincter. The pressure profile in the normal anal canal, at rest, was asymmetric with the highest pressure recorded in the outermost channels. Rectal distension caused a transient increase in the activity of the external sphincter, which was associated with an increase in anal pressure, particularly in the outermost two channels. This was followed by a symmetrical reduction in anal pressure throughout the anal canal, caused by relaxation of the internal sphincter and shortening of the high-pressure zone. Two patterns of response were observed in the patients with idiopathic incontinence. Twelve patients (group 1) showed normal anal relaxation, but the maximum anal pressures recorded during rectal distension or a conscious squeeze were abnormally low, suggesting weakness of the external anal sphincter. The remaining six subjects (group 2), who were older than the group 1 patients, had much lower resting pressures and showed only external sphincter contraction in response to rectal distension, with no obvious internal sphincter relaxation. However, the maximum pressures recorded during a conscious contraction of the external sphincter were lower in this group than in the normal control subjects. These results suggest that group 2 patients have impaired internal anal sphincter tone, as well as external anal sphincter weakness. This may explain why all except one of the group 2 patients, compared with only 17 per cent of group 1 patients, reported incontinence to both solids and liquids.

Adult↗
PubMed1989

Idiopathic constipation associated with impaired urethrovesical and sacral reflex function.

Sixteen chronically constipated women (age range 20-66 years) and 29 healthy control subjects (age range 22-53 years) underwent neurophysiological assessment of the integrity of pelvic spinal reflexes. The results were compared with videourodynamic studies and multiport anorectal manometry combined with external anal sphincter electromyography. The neurophysiological assessment consisted of electrical stimulation of the dorsogenital nerve, while recording any evoked reflex activity in the external anal and urethral sphincters with concentric needle and surface electrodes. Of these constipated women, 75 per cent had absence of one or more evoked sacral reflexes (compared with 20 per cent of healthy controls, P less than 0.05). Sensory thresholds and motor unit potentials in the external anal sphincter were similar in healthy and constipated women. Nine (56 per cent) constipated women displayed urodynamic abnormalities (increased bladder capacity, acontractile bladder and genuine stress incontinence). Only 38 per cent of constipated women perceived a desire to defaecate during rectal distension with up to 100 ml, compared with 95 per cent of normal subjects (P less than 0.0005). Moreover, 73 per cent of constipated women did not relax the external anal sphincter during defaecation, compared with 12 per cent of controls (P = 0.001). Taking into account the possible significance of our data in relation to previous findings it is suggested that the integration of sensory information within the sacral cord may be impaired in chronic idiopathic constipation.

Adult↗
PubMed1989

Anorectal function in normal human subjects: effect of gender.

Multiport anorectal manometry and external anal sphincter (EAS) and internal anal sphincter (IAS) electromyography were conducted in 15 males (41 +/- 3 years) and 20 females (43 +/- 2 years; 5 nulliparous) during rest, maximum conscious sphincter contraction, rectal distension and increases in intra-abdominal pressure. The basal pressure declined within 15 minutes of insertion of the manometric probe to a stable plateau, 55 +/- 4% of the initial value. The maximum basal (91 +/- 5 vs 61 +/- 6 cm water; mean +/- SEM), minimum basal (43 +/- 7 vs 27 +/- 3 cm water) and the maximum squeeze pressures (257 +/- 20 vs 107 +/- 13 cm water) were higher (p less than 0.05) in males than females. Distension of a rectal balloon caused a reduction in pressure in all anal channels, that increased in depth and duration as the distending volume was increased. These anal relaxations were associated with rectal contractions and transient increases in the electrical activity of the EAS. Upon deflating the balloon, the anal pressure increased to values that exceeded the pre-inflation values. The pre-inflation (89 +/- 4 vs 49 +/- 4 cm water), post-inflation (104 +/- 9 vs 62 +/- 7 cm water) and residual (47 +/- 4 vs 30 +/- 2 cm water) pressures during rectal distension were significantly higher in males than in females (p less than 0.05). The higher residual pressure in males was associated with a higher EAS index during rectal distension (0.94 +/- 0.10 vs 0.65 +/- 0.10 mv s; p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗