Anismus in chronic constipation

Constipation and paradoxical puborectalis contraction in anismus and Parkinson's disease: a dystonic phenomenon?

Anismus, or constipation due to functional obstruction at the pelvic outlet by paradoxical contraction of the striated sphincter muscles during defaecation straining, is described in ten constipated patients and four patients with Parkinson's disease and constipation. The dysfunctional pattern of muscle recruitment resembled that characteristic of dystonia elsewhere in the body and was indistinguishable in patients with idiopathic anismus and those with extrapyramidal motor disturbance due to Parkinson's disease. These findings suggest that anismus may be a focal dystonic phenomenon.

Pelvic floor physiology

Pelvic floor physiology is poorly understood. The funnel shape of the pelvic floor and anal canal is uniquely developed to provide discriminatory continence of gas, liquid, and solid. Proximally, the pelvic floor consists of the pubococcygeus and iliococcygeus muscles. Distally, the anal canal is surrounded by the internal and external sphincter muscles. The anorectal ring is situated between the proximal pelvic floor and the distal anal canal. It is the site of the puborectalis muscle, which is anatomically, neurologically, and functionally merged with the deep portion of the external sphincter muscle. It is at this site that unique forces act to create both a flutter valve and the anorectal angle with the flap valve. Extrinsic pressures at this level reinforce both the flap valve and the flutter valve. Intrinsic pressures are generated by all of the surrounding muscles to produce a high-pressure zone. These factors are critical, but many other factors, such as rectal capacity, compliance, colonic transit, motility, and sensory mechanisms, also interact in a complex way to provide normal continence and defecation. Not surprisingly, no single test allows a complete assessment of the interactions of all these factors. Nevertheless, analysis of components thought to be important in pelvic floor physiology has contributed significantly to the understanding of normal as well as abnormal physiology. Although clinical evaluation continues to be the cornerstone of the diagnosis of pelvic floor disorders, anorectal physiological testing has contributed significantly to our understanding of the dynamics of the pelvic floor. With the refinement of existing techniques and the addition of new investigative tools, it is anticipated that knowledge of pelvic floor physiology will continue to grow.

Function of the striated anal sphincter during straining in control subjects and constipated patients with a radiologically normal rectum or idiopathic megacolon

The function of the striated anal sphincter during defaecation straining was recorded by manometry and electromyography (E.M.G.) in 31 constipated patients who were unable to expel a water-filled rectal balloon with effort. This group was divided on the basis of measurement of colonic diameter into those with megacolon and those with a normal sized colon. The latter group was further divided into those with normal transit and those with slow transit. The results were compared with those recorded from 15 control subjects with normal bowel function. With straining, anal pressure fell in 12 of 15 controls while in 3 it increased. In 30 of 31 constipated patients, anal pressure rose paradoxically with straining. Electromyographic recording in controls during straining demonstrated decreased activity in 5, in 4 no change and in 5 an increase in activity. In 28 of 31 constipated patients E.M.G. activity increased with straining. These results suggest that external sphincter contraction during straining occurs in some normal subjects but more frequently among patients with constipation of different types.

Treatment of anismus in intractable constipation with botulinum A toxin

In seven patients with anismus the striated sphincter muscle complex was selectively weakened by local injection of Clostridium botulinum type A toxin. Symptom scores improved significantly and correlated with a significant reduction in the maximum voluntary and canal squeeze pressure and a significant increase in the anorectal angle on straining. Botulinum A toxin seems to be promising treatment for some patients with anismus.

Megarectum

Evaluation of the rectum by barium enema does not correlate well with rectometrographic studies and is not predictive of bowel function. The purpose of the present study was to describe clinical and functional data in patients with chronic idiopathic constipation, where a megarectum was diagnosed by a rectometrogram. Among 355 patients who underwent rectal elasticity studies, 35 were found to have a megarectum (maximum tolerable volume above 320 ml in women and 440 in men) for which no specific etiology was recognized. They, and a group of 11 healthy controls who were not sensitive to stress, underwent studies of stool frequency, colonic transit time of radiopaque markers, rectal elasticity, and anorectal pressures and reflexes. The elasticity coefficient of the rectal wall was decreased in patients as compared to controls (P less than 0.01). Seven patients had onset of symptoms at birth, with maximum tolerable volume in the rectum between 460 and 900 ml, and all were incontinent for feces. Studies of colonic transit times demonstrated normal function in the right and left colon, but there was rectosigmoid stagnation (transit time of 122 +/- 17 hr vs 8 +/- 2 in stress-free controls; X +/- SE; P less than 0.001). In the other 28 patients (late-onset megarectum), in contrast to the congenital group, there was a marked female preponderance, and their recorded stool frequency (4 +/- 0.7/week) was greater than the recalled frequency (1.4 +/- 0.2/week; P less than 0.001). Only half suffered from fecal incontinence. They did not have a greater rectal capacity when colonic transit times were prolonged (455 +/- 27 ml) than when normal (422 +/- 27). Rectal pressure was similar at the level of conscious sensation of filling, regardless of rectal capacity, suggesting a motor, rather than a sensory, abnormality. The amplitude of the rectoanal inhibitory reflex was decreased (P less than 0.001) as compared to controls, sometimes mimicking the findings of Hirschsprung's disease, but increasing rectal distension always induced a relaxation of the internal anal sphincter. The notion of a megarectum, which tolerates large amounts of fluid without sensation, lacks elasticity, and is accompanied by an abnormal rectoanal inhibitory reflex, provides an explanation for one of the mechanisms of constipation by outlet obstruction.

Slow transit constipation. Comparison between patients with or without previous hysterectomy

We have studied 31 patients with slow transit constipation. Fourteen developed severe symptoms following a hysterectomy, while the remainder had symptoms arising de novo and unrelated to pelvic surgery. To establish whether there were specific abnormalities which might be linked to hysterectomy, we compared the two groups. Rectosigmoid motility was impaired in the de novo group. Functional sphincter length, maximum resting anal canal pressure, and the rectoanal inhibitory reflex were not significantly different from controls. The majority of patients were able to significantly increase the anorectal angle on straining to defecate. Patients in the de novo group had a higher sensory threshold for rectal filling compared with controls, whereas the posthysterectomy group was not significantly different. Electromyography of the external sphincter showed failure of appropriate inhibition of resting activity in 57% of the de novo and 38% of posthysterectomy patients. The de novo group had hypoactivity of the rectosigmoid and an insensitive rectum. The abnormality in the hysterectomy group is less clear and any precise link between slow transit constipation and hysterectomy remains obscure.

Dynamic scanning defines a colonic defect in severe idiopathic constipation

A technique is described in which a chemical stimulus applied to the mucosa of the right colon is used to assess colonic motor function. Peroral intubation of the right colon was achieved using a fine polyvinylchloride (PVC) tube. Bisacodyl was used to initiate colonic motor activity, and colonic transit was monitored using 99mTc-DPTA and a gamma camera. In normal subjects there was rapid movement of the radiopharmaceutical from the right colon to the rectum. In patients with severe idiopathic constipation, a spectrum of colonic abnormality was observed from slow transit involving the rectum and sigmoid only to slow transit involving the whole colon. The hepatic flexure to rectum transit time for the 'head of the isotope column' in normals ranged from 1-10 minutes (mean 5.3 minutes), whereas in patients the transit time was 14-25 minutes in four patients and radioisotope did not reach the rectum by two hours in three other patients (controls v patients, p less than 0.01). Patients also showed relatively impaired transport of the isotope 'mass'. This technique has shown that the normal colon is capable of rapid effective transport in response to a standard stimulus, and that patients with severe idiopathic constipation have a definable colonic motor disorder.

Lateral division of the puborectalis muscle in the management of severe constipation

Patients with severe constipation often do not 'relax' their pelvic floor during defaecation. Electromyography of the pelvic floor may reveal inappropriate contraction during defaecation straining, and balloon expulsion, a test of rectal evacuation, may be impaired. Fifteen patients with severe idiopathic constipation and three patients with a megarectum underwent lateral division of the puborectalis muscle and upper half of the external sphincter muscle. Twelve patients had a unilateral division and six patients had both sides divided. Surgery caused a marked reduction in the maximum voluntary squeeze pressure in the anal canal from a pre-operative mean of 90 +/- 49 (s.d.) cmH2O to a postoperative mean of 40 +/- 29 cmH2O (P less than 0.0001). Four patients, three with idiopathic constipation and one with megarectum, experienced symptomatic improvement. Three of these patients had a bilateral division. Improvement did not correlate with a change in the puborectalis electromyography or the ability to expel a balloon. Three patients experienced mild mucus or urge incontinence, but no patient was incontinent for solid stool.

Neurophysiological dysfunction in young women with intractable constipation

Fifteen women with intractable chronic idiopathic constipation dating from adolescence were investigated by anorectal manometry, neurophysiological evaluation of the conus medullaris and external anal sphincter. Comparison was made with 25 asymptomatic female control subjects. Urological disturbances were common amongst the constipated, in five of whom incidental lumbosacral spinal dysraphism was found. No differences in sphincter pressures or the rectosphincteric reflex were demonstrable between the two groups. Rectal defecatory sensation was blunted and the compliance was increased in the constipated group. The latency of the pudendo-anal reflex was significantly prolonged in idiopathic constipation, two women having an absent reflex (greater than 100 ms). Mean motor unit potential duration of the external anal sphincter was not significantly prolonged in the eight constipated women tested. A central neurogenic deficit is postulated in some women with this disorder.

Outcome of colectomy for severe idiopathic constipation

Severe idiopathic constipation affects predominantly young women. We have evaluated the results of colectomy in 44 women with a normal diameter colon and with a median bowel frequency of once per four weeks. The operations were done in one hospital over a 15 year period. After operation 22 patients had normal bowel frequency, 17 diarrhoea (greater than three bowel actions/day), and five persistent or recurrent constipation (interval between bowel actions at least three days). Many patients continued to experience abdominal pain (98% preoperatively v 71% postoperatively); straining and laxative use were still common after surgery. Ten patients needed psychiatric treatment for severe psychological disorders. The preoperative abnormalities of paradoxical contraction of the pelvic floor during straining and impaired rectal evacuation of a water filled balloon did not correlate with the outcome.

Encopresis and constipation in children

Chronic retentive constipation in children is common, often undertreated, and frequently resistant to standard treatment. A new understanding of abnormal defecation dynamics has evolved to complement the established medical behavior model of this condition. The primary care pediatrician is in an excellent position to facilitate prevention through counseling on normal bowel habits and early intervention. A comprehensive medical behavior intervention program can be supervised effectively by the pediatrician providing benefit to most patients. Those who are compliant with treatment and are resistant to intervention may benefit by extensive evaluation of anorectal dynamics and use of such teaching as biofeedback training.

Radiologic studies of rectal evacuation in adults with idiopathic constipation

A consecutive series of 58 patients with idiopathic constipation and 20 control subjects were studied by evacuation proctography and measurements were made of changes during rectal expulsion. A wide range was found in the control group. The anorectal angle, pelvic floor descent, and the presence or size of an anterior rectocele did not discriminate between the control and patient groups. Internal intussusception was rare. Among constipated patients, the only significant differences from normal were in the time taken to expel barium and the amount of barium remaining in the distal rectum. The majority of control subjects (15 of 20) evacuated most of the barium within 20 seconds whereas 45 of 58 constipated patients took a longer time. Using the area of barium on a lateral view of the rectum as a measure, 19 of 20 control subjects evacuated at least 60 percent of the barium from the distal 4 cm of the rectum compared with only 25 of 58 patients. A varying degree of defecatory impairment was thus established among many patients with constipation. The patients were subdivided into those with a normal or abnormal whole gut transit rate as an indication of colonic function, and those who did or did not need to digitally evacuate the rectum as a clinical manifestation of an anorectal disorder. No obvious differences were found between these subgroups using the parameters measured.

Relationship between results of radiological pelvic floor study and anorectal manometry in patients consulting for constipation

The aim of this study was to assess (a) the incidence of perineal descent and (b) the relationship between radiological abnormalities of the pelvic floor and rectoanal manometric disturbances in patients consulting for constipation. Lateral radiographs in both the left lateral and supine positions studied pelvic floor descent. Results obtained in the 25 patients (mean age 47 years) studied were compared with those of 12 controls (mean age 58 years). Pelvic floor descent, never seen in controls, was demonstrated in 14 patients who were older (53 +/- 3 years, mean +/- SD) than the 11 with a normal radiological examination (38 +/- 3 years, p less than 0.05). Anal low pressures (3 cases) and a low amplitude of rectoanal inhibitory reflex (RAIR) (5 cases) were shown only in patients with perineal descent and anal high pressures only in those with normal radiology. Our results suggest that (a) perineal descent is a common finding in over 50% of constipated patients and (b) anorectal motility is related to pelvic floor function.

Idiopathic chronic constipation is associated with decreased colonic vasoactive intestinal peptide

To investigate the reported association between idiopathic chronic constipation and morphologic abnormalities of enteric nerves, we measured the concentrations of six neuropeptides, vasoactive intestinal peptide, peptide histidine-methionine, substance P, methionine5-enkephalin, neuropeptide Y, and the bombesinlike intestinal peptides, in descending colon from 4 patients with idiopathic chronic constipation. Decreased concentrations of vasoactive intestinal peptide (707 +/- 112 ng/g wet tissue) and peptide histidine-methionine (543 +/- 58 ng/g) were found in the muscularis externa obtained from constipated patients compared with normal concentrations (40 patients) of vasoactive intestinal peptide (1199 +/- 47 ng/g) and peptide histidine-methionine (815 +/- 45 ng/g). Vasoactive intestinal peptide was identified by immunocytochemistry in nerve fibers within the circular smooth muscle layer of descending colon obtained from 6 control patients, but not in nerve fibers within the circular smooth muscle of descending colon obtained from 3 patients with idiopathic chronic constipation. By contrast, the distribution of immunoreactive met5-enkephalin was similar in normal descending colon and in descending colon obtained from patients with idiopathic chronic constipation. Decreased colonic concentrations of vasoactive intestinal peptide (a candidate nonadrenergic, noncholinergic inhibitory neurotransmitter) may be associated with diminution of inhibitory innervation of colonic circular smooth muscle in some patients with idiopathic chronic constipation.

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.

Is paradoxical contraction of puborectalis muscle of functional importance?

Paradoxical contraction of the puborectalis muscle during simulated defecation straining (anismus) has been cited as a cause of constipation. The functional specificity of this phenomenon was evaluated in 79 patients, 50 with constipation, 21 with idiopathic perineal pain, and eight with solitary rectal ulcer syndrome. Electromyogram evidence of paradoxical puborectalis contraction was observed in 38 (76 percent), ten (48 percent), and four (50 percent) of these patients, respectively. All patients with solitary rectal ulcer syndrome had difficulty defecating; defecation was normal in all patients with perineal pain. These observations suggest that paradoxical contraction of the puborectalis muscle is not a specific finding, and that it is not the sole cause of constipation in patients with anismus.

Treatment of chronic constipation with cisapride and placebo

The effect of cisapride (20 mg bid), a new prokinetic drug, on bowel habits and laxative consumption was studied in patients with idiopathic painless constipation and chronic laxative intake. After a four week base line period, spontaneous defection (frequency without laxative intake) and total defecation (total frequency) were measured. Patients with a spontaneous defecation of less than three stools per week entered the treatment period and were randomly assigned to double blind treatment with either cisapride (n = 64) or placebo (n = 62). After eight weeks of treatment, a four week run out phase on single blind placebo medication was conducted. Cisapride and placebo increased spontaneous stool frequency from 1.1 +/- 0.2 SEM to 3.0 +/- 0.2 per week (p less than 0.001) and from 1.2 +/- 0.1 to 1.5 +/- 0.2 (p greater than 0.05), respectively. Laxative consumption was decreased from 3.6 +/- 0.3 to 1.8 +/- 0.2 doses/week by cisapride (p less than 0.001) and from 3.3 +/- 0.3 to 2.8 +/- 0.3 by placebo (p less than 0.05). Both drugs improved constipation as assessed by the patient by means of a visual analogue scale, but cisapride did so to a larger extent than placebo. The effects of cisapride partly outlasted active medication by at least four weeks. It is concluded that cisapride improves bowel habits in patients with idiopathic constipation and reduces laxative consumption.

Diagnosis and surgical management of intractable constipation

Seventy-four patients with intractable constipation, of whom thirty-three had slow and forty-one normal intestinal transit, were investigated to determine the aetiology of their disorder and plan treatment. Patients with slow transit had a greater incidence of abdominal pain and distension (P less than 0.001) and only 9 per cent had a normal call to stool compared with 71 per cent of those with normal transit (P less than 0.001). Internal and sphincter function as assessed by sphincter pressures, length and the recto-anal inhibitory reflex did not reveal any difference between the groups and normal controls; similarly anal sensation and rectal compliance were normal. However, those with normal transit had a higher threshold of rectal sensation than controls (P less than 0.05). Slow transit patients failed to show a postprandial increase in rectosigmoid motility compared with controls (P less than 0.05). Whilst the majority failed to inhibit the external sphincter on bearing down, half of those with normal transit produced either partial or complete inhibition. Both groups were able to increase the anorectal angle on straining. Twenty-two normal transit patients had abnormal perineal descent compared with controls (P less than 0.0005). Patients with perineal descent exhibited abnormal rectal morphology. Rectal intussusception was observed in 13 of 35 evacuation proctograms. On the basis of the data presented, we could not justify internal sphincterotomy of puborectalis division. Our policy in severe slow transit constipation was to offer colectomy and ileorectal anastomosis. In five out of seven to date, a successful result has been achieved. Eight patients with rectal intussusception have undergone an abdominal rectopexy with significant improvement in three. In our hands, the evacuation proctogram and transit studies were the most useful preoperative investigations.

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.

Failure of rectal expulsion as a cause of constipation: why fibre and laxatives sometimes fail

High-fibre diet and laxatives are not always successful in the treatment of severe constipation. In a group of thirteen women with intractable constipation three experimental models of rectal evacuation showed that all had a disorder of defaecation. None could expel 120 ml barium paste as fast or as completely as could ten normal women; six could expel hardly any barium. Only three of the thirteen could expel a balloon containing 50 ml water from the rectum, whereas all of six normal subjects could do so easily. Four of the patients with repeated straining efforts could expel no more than 10% of a 500 ml saline enema, whereas six normal subjects rapidly passed 40-80%. It is postulated that dietary and drug treatment designed to soften and increase the bulk of the stools fails to help some patients because they find it difficult to expel even semi-solid or liquid stool. Electromyography showed that these patients tend to contract rather than relax the striated muscle of the pelvic floor on attempted defaecation. Their failure to defaecate is due to incoordination of the pelvic floor rather than an abnormality of the stool or a disorder of the colon.

New method for the dynamic assessment of anorectal function in constipation

A new dynamic technique for the investigation of anorectal function has been developed. This involves radiological visualization of the rectum during voiding of a semisolid radio-opaque contrast medium, and simultaneous measurement of the intrarectal pressure and electrical activity of the external anal sphincter. The method has been used to study patients (n = 16) with profound difficulty passing formed stool. It has demonstrated an abnormal increase in the activity of the puborectalis and superficial and sphincter muscles during voiding in these patients, compared with normal subjects (n = 6). The inability to void was associated with failure to widen the anorectal angle on straining.

Pelvic motility and response to intraluminal bisacodyl in slow-transit constipation

The resting motility of the pelvic colon was studied in 28 patients with constipation and compared with control subjects and patients with diarrhea. Colonic activity in patients who had been shown to have slow colonic transit was not significantly different from controls. In contrast, activity in patients who complained of constipation but who were found to have normal colonic transit time was increased (P less than 0.02). The response of the pelvic colon to the introduction of a surface-acting laxative was studied in 18 patients with slow-transit constipation. Eleven patients developed progressive peristaltic waves, while in 7 there was no response. It is possible that the relative inactivity of the colon in the latter group is due to a disorder of the myenteric plexus. If so, the bisacodyl stimulation test may distinguish patients with an abnormal myenteric plexus from those in whom it is normal.