The mechanics of the anal sphincter complex.

The anal sphincter complex consists of circumferentially arranged muscle fibres, which surround a relatively thick anal lining. This apparatus was modelled mechanistically as two concentric homogeneous isotropic linear elastic cylinders. The inner cylinder (anal lining) was considered to be thick walled, while the outer (the circular muscle) was assumed to be thin walled. The model predicts that the anal sphincter tension varies linearly with luminal diameter. This prediction was confirmed experimentally under normal conditions as well as during external sphincter contraction and internal sphincter relaxation. Under conditions of negligible hoop stress in the anal lining the model also predicts that the intra-luminal pressure falls to zero before the luminal diameter reaches zero. Hence, an autoregulatory mechanism of anal cushion thickening, as the luminal pressure falls to zero, to produce anal closure was proposed. Deficiencies in this autoregulation mechanism may explain anal incontinence and the obstructed defaecation often found in subjects with haemorrhoids.

A haematuria diagnostic service in a district general hospital.

Four years experience of a haematuria diagnostic service in a District General Hospital, comprising 215 patients, has identified 42 new cases of bladder cancer, 5 of renal cell cancer and 3 of renal pelvis cancer. Urine and blood tests were non-contributory in their diagnosis but intravenous urography was diagnostic in the majority. The period of time between presentation to the general practitioner and treatment of the cancer has been reduced to less than the time normally spent on the Out-Patient waiting list.

Peristomal varices--life threatening or luminal?

Bleeding from the edge of an ileostomy site is a common problem. In those who have undergone a proctocolectomy with ileostomy formation in conjunction with a risk of chronic liver disease (even with normal liver function tests), this may be due to peristomal varices. If this is the case, significant, difficult-to-control and potentially life-threatening bleeding is likely in the future and may require transfusion. Improvements in radiological imaging techniques can give quick, sensitive and specific information to diagnose and guide management in this group. In those patients with major bleeding episodes, an initial conservative management policy should be adopted with the knowledge that, if bleeding persists, propanolol therapy, portosystemic shunt insertion or even liver transplantation may be indicated.

Preservation of faecal continence during rises in intra-abdominal pressure: is there a role for the flap valve?

Studies were carried out in 15 normal subjects and 14 patients with idiopathic faecal incontinence to test whether a rectoanal flap valve could be responsible for maintaining faecal continence in man. Intraluminal pressures were recorded from the rectum and from three sites in the anal canal during serial increases in intra-abdominal pressure, produced by forced expiration into a sphygmomanometer keeping the height of the column of mercury at prescribed levels. The anal pressures in the normal volunteers always remained higher than the intrarectal pressures even when these were as high as 230 cm H2O. This pressure gradient was the reverse of that which would be found if an anterior rectal flap valve maintained continence and suggests instead that continence is normally maintained by a reflex contraction of the external anal sphincter. The anal pressures in patients with idiopathic faecal incontinence, however, fell below the rectal pressure as the intra-abdominal pressure increased, creating the conditions for a flap valve. The valve was incompetent, however, because fluid infused into the rectum leaked from the anus whenever the rectal pressure exceeded the anal pressure.

Effect of aging on anorectal function.

Measurements of anorectal function were conducted on 37 elderly (66-87 years) and 48 young (19-55 years) normal subjects. Elderly subjects had decreased anal pressures compared with younger subjects, required lower rectal volumes to inhibit anal sphincter tone and had increased rectal pressures upon balloon distension. The rectal volume required to cause the desire to defecate and the maximum tolerated volume were lower in the elderly, but the corresponding rectal pressures were similar, indicating the sensations were mediated by tension, or pressure receptors. Rectal contractions were generated at similar degrees of rectal distension. A lower proportion of elderly, compared with young subjects could defecate a sphere 18 mm in diameter within 20 seconds. The degree of perineal descent was greater in the elderly female subjects compared with the young women, although there was no difference in this measurement between men. The anorectal angle was similar in young and old. The changes in anorectal function in the elderly would tend to make them more susceptible to faecal incontinence.

Role of constipation and anal hypertonia in the pathogenesis of haemorrhoids.

The hypothesis that haemorrhoids result from chronic constipation was investigated by studying bowel habit, anal pressure profiles and anal compliance in 13 men and 10 women with prolapsing haemorrhoids, 12 women with severe constipation and 14 male and 11 female control subjects. Defaecation was less frequent in women than in men (P less than 0.01) but was independent of the presence of haemorrhoids. Patients with haemorrhoids and control subjects reported similar stool consistency and rarely admitted to straining. Severely constipated women complained of infrequent defaecation, straining at stool and hard motions, but none had prolapsing haemorrhoids. Haemorrhoids were associated with significantly longer anal high-pressure zones and significantly greater maximum resting pressures at all levels of anal distension (P less than 0.01), but minimum residual pressure during rectal distension and maximum squeeze pressure were not significantly different from control subjects. Maximum resting pressure was increased in patients of both sexes with haemorrhoids, but this reached statistical significance only in men (P less than 0.001). Constipated women had normal anal pressure profiles and maximum anal pressures. These data show that patients with haemorrhoids are not necessarily constipated but tend to have abnormal anal pressure profiles and anal compliance. Chronically constipated women do not necessarily have haemorrhoids but have normal anal pressure profiles and compliance. This casts doubt upon the hypothesis that haemorrhoids are caused by constipation.

Phosphorc onverter camera for near-infrared laser-beam profile recording.

A compact camera system, made up of an IR sensitive phosphor activated by a photographic flashgun and with Polaroid film recording, has been developed for use in laser beam diagnostics at 1.315 microm. Detection thresholds, phosphor camera sensitivity, linearity, saturation, and time response have been determined. Estimates are made of the performance of a phosphor combined with an electronic system based on silicon vidicons or photodiode arrays.

An analysis of anal sphincter pressure and anal compliance in normal subjects.

To investigate anal sphincter mechanics, anal pressure was measured in 14 normal males and 11 normal females using probes of 0.4 to 3 cm in diameter. Resting pressure profiles on insertion and withdrawal did not differ significantly. Anteroposterior pressure differences could be explained by leverage of rigid probes against the anterior rectal wall. A maximal voluntary squeeze increased pressure throughout the anus, whereas the recto-anal inhibitory reflex resulted in a greater reduction in pressure in the upper part of the anal canal. Resting pressure, squeeze pressure and minimum residual pressure (during rectal distension) rose with increasing anal diameter. Estimated sphincter tension was linearly related to anal diameter and the slope of this relationship was increased by sphincter contraction and reduced by sphincter relaxation. The deviation from linearity of this relationship at low anal diameters may be due to swelling of the anal cushions to maintain anal pressure when muscular tension approaches zero.

Effect of stool size and consistency on defecation.

The ability of subjects to expel from the rectum objects simulating stools of different characteristics was assessed in paired studies carried out in a total of 58 normal subjects and 25 young women with severe constipation. Our results showed that a lower percentage of normal subjects and a lower percentage of constipated patients were able to pass a 1.8 cm incompressible sphere compared with a 50 ml deformable balloon, although constipated patients found it more difficult than normal subjects to expel both types of simulated stool. It was also more difficult for normal subjects to pass a soft compressible silicon rubber simulated stool than a stool made up of a similar volume of incompressible 1 cm wooden spheres contained in a cylindrical latex envelope, but both objects were much easier to pass than the same number of 1 cm spheres placed loose within the rectum. When normal subjects were instructed to expel single incompressible spheres of different sizes placed in the rectal ampulla, the intrarectal pressure and the time needed to pass these objects varied inversely with their diameter. These results suggest that more effort is required to expel stools from the rectum if they are small and hard than if they are large and soft.

Effect of bile acid on anorectal function in man.

The effects of rectal infusions (500 ml) of deoxycholic acid (1 mmol/l, 3 mmol/l) or normal saline on basal anorectal motility and responses to rectal distension were studied in 11 normal volunteers. Deoxycholic acid (1 mmol/l) did not alter anorectal motor patterns under basal conditions but reduced the rectal volumes required to induce a desire to defecate (deoxycholic acid 76 (12) ml v saline 123 (12) ml; mean (SEM) p less than 0.01), and to produce anal relaxation (deoxycholic acid 83 (14) ml v saline 152 (24) ml; p less than 0.05) and perception of the rectal balloon (deoxycholic acid 56 (10) ml v saline 104 (17) ml; p less than 0.01) that were sustained for the period of distension (1 min). Seven of 10 subjects could not tolerate an infusion of 3 mmol/l deoxycholic acid. Between two and 30 minutes after the start of the infusion they experienced an extreme urge to defecate which was associated with large amplitude pressure waves in the rectal channels (amplitude 30 (5) mmHg, duration 0.7 (0.1) min, frequency 1.7 (0.4)/min). Such contractions were never seen during saline infusion. Thus, rectal infusion of deoxycholic acid at physiological concentrations increases the sensitivity of the rectum to distension, and promotes an urgent desire to defecate in normal subjects.

Urological abnormalities in young women with severe constipation.

Anorectal and urodynamic studies were carried out in 10 young women with severe constipation and the results compared with those obtained in controls. The lowest volumes that provoked a desire to defecate (constipated 200 +/- 50 v controls 110 +/- 10 [mean +/- SEM] ml: p less than 0.05), and a desire to micturate (constipated 560 +/- 40 v controls 295 +/- 15 [mean +/- SEM] ml: p less than 0.001), were significantly greater in constipated patients compared with controls. The maximum tolerable rectal volume (380 +/- 30 v 290 +/- 20 [mean +/- SEM] ml: p less than 0.05) and the bladder capacity (720 +/- 50 v 540 +/- 10 [mean +/- SEM] ml: p less than 0.001) were also increased in the constipated subjects compared with controls. Electromyographic studies show failure of relaxation of the external anal sphincter (EAS) on attempted defecation in all 10 patients; and eight of these patients actually contracted their EAS when they strained to defecate, causing a functional outlet obstruction. Urodynamic studies showed normal urinary flow rates, normal detrusor pressures and normal radiology during voiding. Thus, these studies suggest that constipated patients have an increase in capacity and a reduction in sensitivity in the urinary bladder as well as in the rectum, but showed no evidence of obstruction to urine flow.

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.

Physiological studies in young women with chronic constipation.

Manometric, radiological and neurophysiological investigations were performed on 34 women, aged between 14 and 53, who suffered with chronic constipation refractory to treatment, and on 27 age-matched normal female control subjects. The constipated patients had more difficulty in evacuating simulated stools than control subjects and 13 out of 19 patients tested obstructed defaecation by contracting the external sphincter during straining. The constipated group required a greater degree of rectal distension than control subjects to induce rectal contractions, anal relaxation and a desire to defaecate. Other modalities of rectal sensation were normal in the constipated subjects. Compared with controls, constipated patients had significantly lower anal pressures, an abnormal degree of perineal descent on straining and an obtuse anorectal angulation at rest. These results were compatible with weakness of the pelvic floor and neuropathic damage to the external sphincter. Mouth to anus transit time was abnormally prolonged in 60% of constipated patients, but was within the normal range in the remainder. Anorectal function in patients with slow transit was not significantly different from that in patients with a normal transit time. The mouth to caecum transit time of a standard meal was prolonged in constipated patients irrespective of the duration of the whole gut transit. Gastric emptying was not significantly prolonged.

Local recurrence after low anterior resection using the staple gun.

Eleven early anastomotic recurrences have occurred after 34 low anterior resections for carcinoma of the rectum performed during the past 2 years using the EEA staple gun. These recurrences all occurred after resection of locally advanced tumours and caused distressing symptoms, and it is suggested that this technique might be best reserved for more favourable growths.

Impairment of defecation in young women with severe constipation.

Anorectal manometry, radiology, and tests of simulated defecation were carried out in 14 severely constipated young women and 29 age-matched controls. The resting anal sphincter pressures were reduced in the patients, but the squeeze pressures, rectoanal inhibitory reflex, and rectal pressures upon balloon distention were all normal. At rest, the anorectal angle was more obtuse in the constipated group, but there was no overall increase in perineal descent in constipated patients compared with controls. The presence of a balloon in the rectum and the onset of pain were perceived in constipated patients at volumes that were not significantly different from those in normal volunteers. Constipated patients, however, required higher rectal volumes to induce the desire to defecate and to stimulate regular rectal contractions. Constipated patients also found it more difficult to pass simulated stools from the rectum than the normal controls and, unlike most normal controls, failed to inhibit their external anal sphincter on attempted defecation. These findings suggest that young women with severe constipation have great difficulty initiating the coordinated set of events that constitute a normal defecation response.

Anorectal sensitivity and responses to rectal distention in patients with ulcerative colitis.

Anorectal function in ulcerative colitis was assessed by measuring pressures at multiple sites in the anus and rectum under basal conditions and during balloon distention of the rectum in 29 patients with ulcerative colitis (12 active, 11 quiescent, and 6 during both phases) and in 12 normal controls. Resting and squeeze sphincter pressures were similar in the three groups. The lowest rectal volume that could be perceived, the volume required to induce a desire to defecate, and the maximum tolerable rectal volume were all lower in patients with active colitis than in patients with quiescent colitis (p less than 0.001) and controls (p less than 0.001). The rectal volume required to cause a sustained anal relaxation was lower in patients with active colitis (p less than 0.05) than in controls. Both peak and steady state rectal pressures in response to rectal distention were significantly higher in patients with active colitis than in patients with quiescent colitis (p less than 0.05) and controls (p less than 0.02). Paired studies showed that during remission of disease there was a decrease in rectal sensitivity (p less than 0.05) and an increase in rectal compliance (p less than 0.05). These results suggest that the frequent and urgent defecation, i.e., the predominant feature of active colitis, is related to a hypersensitive and poorly compliant rectum, which, upon distention, is more reactive and is more likely to induce prolonged sphincter relaxation.

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.