Magnetic resonance imaging of anatomic and dynamic defects of the pelvic floor in defecatory disorders

OBJECTIVE: Endoanal ultrasound identifies anal sphincter anatomy, and evacuation proctography visualizes pelvic floor motion during simulated defecation. These complementary techniques can evaluate obstructed defecation and fecal incontinence. Our aim was to develop a single, nonionizing, minimally invasive modality to image global pelvic floor anatomy and motion. METHODS: We studied six patients with fecal incontinence and seven patients with obstructed defecation. The anal sphincters were imaged with an endoanal magnetic resonance imaging (MRI) coil and endoanal ultrasound (five patients). MR fluoroscopy acquired images every 1.4-2 s, using a modified real-time, T2-weighted, single-shot, fast-spin echo sequence, recording motion as patients squeezed pelvic floor muscles and expelled ultrasound gel; no contrast was added to other pelvic organs. Six patients also had scintigraphic defecography. RESULTS: Endoanal ultrasound and MRI were comparable for imaging defects of the internal and external sphincters. Only MRI revealed puborectalis and/or external sphincter atrophy; four of these patients had fecal incontinence. MR fluoroscopy recorded pelvic floor contraction during squeeze and recorded relaxation during simulated defecation. Corresponding comparisons for angle change and perineal descent during defecation were not significant; only MRI, but not scintigraphy, identified excessive perineal descent in two patients. CONCLUSIONS: Pelvic MRI is a promising single, comprehensive, nonradioactive modality to measure structural and functional pelvic floor disturbances in defecatory disorders. This method may provide insights into mechanisms of normal and disordered pelvic floor function in health and disease.     

Phenotypic variation in functional disorders of defecation

BACKGROUND & AIMS: Although obstructed defecation is generally attributed to pelvic floor dyssynergia, clinical observations suggest a wider spectrum of anorectal disturbances. Our aim was to characterize phenotypic variability in constipated patients by anorectal assessments. METHODS: Anal pressures, rectal balloon expulsion, rectal sensation, and pelvic floor structure (by endoanal magnetic resonance imaging) and motion (by dynamic magnetic resonance imaging) were assessed in 52 constipated women and 41 age-matched asymptomatic women. Phenotypes were characterized in patients by principal components analysis of these measurements. RESULTS: Among patients, 16 had a hypertensive anal sphincter, 41 had an abnormal rectal balloon expulsion test, and 20 had abnormal rectal sensation. Forty-nine patients (94%) had abnormal pelvic floor motion during evacuation and/or squeeze. After correcting for age and body mass index, 3 principal components explained 71% of variance between patients. These factors were weighted most strongly by perineal descent during evacuation (factor 1), anorectal location at rest (factor 2), and anal resting pressure (factor 3). Factors 1 and 3 discriminated between controls and patients. Compared with patients with normal (n = 23) or reduced (n = 18) perineal descent, patients with increased (n = 11) descent were more likely (P < or = .01) to be obese, have an anal resting pressure >90 mm Hg, and have a normal rectal balloon expulsion test result. CONCLUSIONS: These observations demonstrate that functional defecation disorders comprise a heterogeneous entity that can be subcharacterized by perineal descent during defecation, perineal location at rest, and anal resting pressure. Further studies are needed to ascertain if the phenotypes reflect differences in the natural history of these disorders.     

Anorectal Physiology and Pathophysiology

The anatomy and physiology of the external anal sphincter, puborectalis muscle, internal anal sphincter, and rectum are described. Measurement techniques are reviewed emphasizing those which can be carried out by the gastroenterologist in independent office practice, and the range of normal values for each test is given. A protocol for diagnostic evaluation of anorectal disorders is recommended which includes testing for rectal prolapse and for descent of the perineum by having the patient strain while seated on a commode chair, evaluating the external and internal anal sphincters by recording EMG with an anal plug, or recording pressures with a perfused catheter or balloon probe, using a rectal balloon to evaluate the maximum tolerable volume of rectal distension and the minimum (threshold) volume of a bolus injection which can be subjectively perceived, and arranging with a radiologist to perform a proctogram--a radiograph of the rectum and anal canal during rest and when the patient strains to defecate--in order to evaluate the anorectal angle (puborectalis muscle) and to detect rectocele and intussusception. These objective tests should be supplemented by a careful clinical history and physical examination.     

Electromyography of the internal anal sphincter performed under endosonographic guidance description of a new method

PURPOSE: The aim of our study was to investigate internal anal sphincter electromyographic signals. METHODS: Electromyography of the internal anal sphincter was performed with platinum wire electrodes in six healthy volunteers (three males and three females), inserted under endosonographic guidance. Platinum wire electrodes were also inserted into the external anal sphincter. Activity of both the internal and external anal sphincter in a 40-second period was measured. RESULTS: Internal anal sphincter median activity was 22.1 (range, 5.5–67.6) μ V. Slow-wave activity was 47 cycles/minute (range, 34–55 cycles/minute). After inflation of a rectal balloon with air until a constant relaxation of the anal canal was obtained, a decrease in internal anal sphincter activity to 15.9 (1.2–31.3) μV as well as a decrease in slow-wave activity to 34 cycles/minute (range, 27–40 cycles/minute) was found. The original internal anal sphincter EMG was resumed after deflation of the rectal balloon. External anal sphincter median activity was 31 (range, 0.77–18.6)μV. During inflation of the rectal balloon, a reflex increase in external sphincter EMG activity was found. With the rectal balloon fully inflated a part of this increase was still present, 11.0 (1.9–24.6)μV. In some of the subjects, this increased activity was superimposed on the internal anal sphincter recordings as well. During a voluntary squeeze it was not possible to identify internal anal sphincter activity due to activity of the external anal sphincter totally overriding the internal anal sphincter signal. CONCLUSION: Precise EMG recordings from the internal anal sphincter is possible with endosonographic guidance of the electrodes, except during voluntary squeezing of the external anal sphincter.     

Anal Sphincter Morphology in Patients With Full-Thickness Rectal Prolapse

PURPOSE: The aim of this study was to assess the morphologic change of the anal canal in patients with rectal prolapse. METHODS: The endoanal ultrasound scans of 18 patients with rectal prolapse were compared with those of 23 asymptomatic controls. The thickness and area of the internal anal sphincter and submucosa were measured at three levels. RESULTS: Qualitatively, patients with rectal prolapse showed a characteristic elliptical morphology in the anal canal with anterior/posterior submucosal distortion accounting for most of the change. Quantitatively, internal anal sphincter (IAS) and submucosa (SM) thicknesses and area were greater in all quadrants of the anal canal (especially upper) in patients with rectal prolapse compared with controls. There was statistical evidence (in a regression model) of a relationship between increases in all measured variables and the finding of rectal prolapse. CONCLUSIONS: The cause of sphincter distortion in rectal prolapse is unknown but may be a response to increased mechanical stress placed on the sphincter from the prolapse or an abnormal response by the sphincter complex to the prolapse. Patients found to have this feature on endoanal ultrasound should undergo clinical examination and defecography to look for rectal wall abnormalities.     

Descending perineum syndrome: audit of clinical and laboratory features and outcome of pelvic floor retraining

Objective: Our aim was to retrospectively analyze the Mayo Clinic experience of descending perineum syndrome from 1987–1997. Methods: Clinical records were abstracted for demographic features, risk factors, results of anorectal and defecation tests, and a mailed questionnaire evaluated outcome and current symptoms. Results: All results are mean ± SD. Clinically, 39 patients (38 women, one man), mean age 53 ± 14 yr, presented with constipation (97%), incomplete rectal evacuation (92%), excessive straining (97%), digital rectal evacuation (38%), and fecal incontinence (15%). Laboratory tests showed anal sphincter resting pressure was 54 ± 26 mm Hg, and squeeze pressure was 96 ± 35 mm Hg; expulsion from the rectum of a 50-ml balloon required > 200 g added weight in 27%; perineal descent was 4.4 ± 1 cm (normal < 4 cm) by scintigraphy. Scintigraphic evacuation, rectoanal angle change during defecation, and perineal descent were abnormal in 23%, 57%, and 78% of the patients, respectively. Associated features included female gender (96%), multiparity with vaginal delivery (55%), hysterectomy or cystocele/rectocele repair (74%). On follow-up, 64% responded; 17 of these 25 responders underwent pelvic floor retraining. At 2-yr median follow-up (range, 1–6 yr), 12 still experienced constipation or excessive straining; their perineal descent was greater than in patients who responded to retraining (   p = 0.005  ). Conclusions: Descending perineum syndrome is identifiable by clinical history and examination, and the most prevalent abnormality on testing is perineal descent > 4 cm; rectal balloon expulsion is an insensitive screening test for descending perineum syndrome. Pelvic floor retraining is a suboptimal treatment for this chronic disorder of rectal evacuation; the extent of perineal descent appears to be a useful predictor of response to retraining.     

Anatomy of the anal sphincters

PURPOSE: A recent application of endosonography in the evaluation of anal sphincter morphology has led to controversy about the possibility of precisely assessing the diameter of external and internal anal sphincter muscles. On the other hand, magnetic resonance imaging (MRI) has been proposed to allow a more detailed view of the anatomy of the pelvic floor. However, both techniques have not yet been compared directly. METHODS: Eight healthy volunteers (age range, 25–40 years; 53, malefemale) participated. Anal ultrasound was performed using a 7.5-MHz rectal transducer which produced a transversal panorama display of 360, allowing an image perpendicular to the anal canal. Imaging of the diameter of the internal and external anal sphincter muscles was performed with the transducer placed in the midanal canal, and measurement was always performed by the same investigator in dorsal projection. MRI was performed using a 1.5 Tesla Magnetom (Siemens, Erlangen, Germany) to obtain sagittal and angled axial (perpendicular to the anal canal) planes for consecutive 3-mm slices which were evaluated by four independent raters. RESULTS: Muscle thickness of the sphincter muscles in dorsal projection was 1.96±0.61 mm for the internal sphincter and 6.35±1.07 mm for the external sphincter using ultrasound. It was 1.72±0.13 mm and 3.99±0.99 mm, respectively, using MRI. When both measures were compared, only the internal sphincter data correlated significantly (r=0.818,P=0.0023) between both measures. Sagittal resonance imaging of the anal canal did not allow for differentiation of both muscles at all. Differentiation among mucosa, submucosa, and internal anal sphincter is not possible with MRI but may well be performed with high-resolution ultrasound. CONCLUSION: Anal ultrasound carries the potential of becoming a routine clinical procedure for evaluation of the anal anatomy and morphology in defecation disorders, but current MRI assessment of the anal anatomy is elaborate, costly, and does not provide any further insights.Supported by Grant En 50/10 from the Deutsche Forschungs-gemeinschaft.Abstract published in Gastroenterology 1994;104:A577.     

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.     

Relationship between symptoms and disordered continence mechanisms in women with idiopathic faecal incontinence

BACKGROUND AND AIMS: Anal sphincter weakness and rectal sensory disturbances contribute to faecal incontinence (FI). Our aims were to investigate the relationship between symptoms, risk factors, and disordered anorectal and pelvic floor functions in FI. METHODS: In 52 women with "idiopathic" FI and 21 age matched asymptomatic women, we assessed symptoms by standardised questionnaire, anal pressures by manometry, anal sphincter appearance by endoanal ultrasound and magnetic resonance imaging (MRI), pelvic floor motion by dynamic MRI, and rectal compliance and sensation by a barostat. RESULTS: The prevalence of anal sphincter injury (by imaging), reduced anal resting pressure (35% of FI), and reduced squeeze pressures (73% of FI) was higher in FI compared with controls. Puborectalis atrophy (by MRI) was associated (p<0.05) with FI and with impaired anorectal motion during pelvic floor contraction. Volume and pressure thresholds for the desire to defecate were lower, indicating rectal hypersensitivity, in FI. The rectal volume at maximum tolerated pressure (that is, rectal capacity) was reduced in 25% of FI; this volume was associated with the symptom of urge FI (p<0.01) and rectal hypersensitivity (p = 0.02). A combination of predictors (age, body mass index, symptoms, obstetric history, and anal sphincter appearance) explained a substantial proportion of the interindividual variation in anal squeeze pressure (45%) and rectal capacity (35%). CONCLUSIONS: Idiopathic FI in women is a multifactorial disorder resulting from one or more of the following: a disordered pelvic barrier (anal sphincters and puborectalis), or rectal capacity or sensation.     

Balloon expulsion test facilitates diagnosis of pelvic floor outlet obstruction due to nonrelaxing puborectalis muscle

We compared balloon expulsion, defecography, colonic transit times, anal manometry, and electromyography in 21 patients with severe constipation. Defecography demonstrated nonrelaxation of the sphincter during straining in all patients. Only 12 patients were unable to expel a balloon. Colonic transit was normal (five) or showed rectosigmoid delay (seven). All 12 patients were offered biofeedback. The nine patients able to expel a balloon had normal colonic transit (six) or colonic inertia (two). Rectosigmoid delay was due to severe intussusception in one patient. Anal manometry and pudendal nerve latencies revealed no difference between those who could and those who could not expel a balloon. Balloon expulsion seems to be a more reliable way to diagnose pelvic floor outlet obstruction due to nonrelaxation of the puborectalis muscle. Nonrelaxation of the sphincter on defecography should be correlated with balloon expulsion and colonic transit studies.Read at the meeting of The American Society of Colon and Rectal Surgeons, St. Louis, Missouri, April 29 to May 4, 1990.     

Defecometry

The parameters of defecation,i.e., maximum rectal pressure increase during straining, duration of effective evacuation, and the work performed to evacuate a simulated stool, can be quantified by defecometry, a new method to evaluate the defecation act. Simultaneous anal pressure records demonstrate the nature of the sphincter activity during simulated defecation. The test was performed on 19 patients with constipation and on 14 controls. Five patients could not evacuate the simulated stool, while five others could, but more laboriously than the remaining nine patients whose defecation was comparable with the controls. Laborious defecation is characterized by longer duration and more performed work during evacuation. Every patient with difficult or ineffective evacuation had sphincter contraction during defecation, whereas this phenomenon was not observed in patients with normal defecation. Defecometry permits more adequate identification and characterization of the outlet-obstruction-type constipated patients than the simple balloon expulsion test and the analysis of sphincter activity during straining with empty rectum in lateral decubitus. Early diagnosis and treatment of patients with outlet obstruction is important to avoid late neuromuscular damage to the pelvic floor.     

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.     

Slow transit of the colon associated with severe constipation after the ripstein operation

Eighteen patients with severe constipation after undergoing the Ripstein operation for rectal prolapse (n = 11) or internal rectal procidentia (n = 7) were studied with defecography, anorectal manometry, electromyography of the external anal sphincter and the puborectalis muscle, colonic transit time, and blood tests. Thirteen patients had slow-transit constipation. None showed a completely normal pattern in the parameters studied. The authors emphasize the importance of careful preoperative investigation to identify the patients who have associated colorectal disturbances together with their rectal prolapse or internal rectal procidentia.Read in part at Collegium Internationale Chirurgiae Digestivae Tenth Congress, Copenhagen 1988.     

Defecation 1: Testing a hypothesis for pelvic striated muscle action to open the anorectum

Background

We conducted an observational study to assess the hypothesis that the pelvic muscles actively open the anorectal lumen during defecation.

Methods

Three groups of female patients were evaluated with video imaging studies of defecation using a grid or bony reference points. Eight patients with idiopathic fecal incontinence had video myogram defecography; eight with obstructive defecation had magnetic resonance imaging (MRI) defecating proctograms; and four normal patients had video X-ray or MRI defecating proctogram studies.

Results

In all three groups, the anorectum was stretched bidirectionally by three directional muscle force vectors acting on the walls of the rectum, effectively doubling the diameter of the rectum during defecation. The anterior rectal wall was pulled forwards, and the posterior wall backwards and downwards opening the anorectal angle, associated with angulation of the anterior tip of the levator plate (LP). These observations are consistent with a staged relaxation of some parts of the pelvic floor during defecation, and contraction of others. First, the puborectalis muscle relaxes. Puborectalis muscle relaxation frees the posterior rectal wall so that it can be stretched and opened by contraction of the LP and conjoint longitudinal muscle of the anus. Second, contraction of the pubococcygeus muscle pulls forward the anterior rectal wall, further increasing the diameter of the rectum. Third, when the bolus has entered the rectum, the external anal sphincter relaxes, and the rectum contracts to expel the fecal bolus.

Conclusions

Our results are consistent with the hypothesis that pelvic striated muscle actively opens the rectal lumen, thereby reducing internal anorectal resistance to expulsion of feces. Controlled studies of electromyographic activity would be useful to further test this hypothesis.     

Radiologic evaluation of anorectal disorders

Defecation is a dynamic event, and although evacuation proctography does not simulate physiologic defecation exactly, it does provide maximal stress to the pelvic floor and image rectal emptying, both of which are required for the diagnosis of certain conditions: MR imaging studies are attractive in that no ionizing radiation is involved, but unless an evacuation study is performed, the features of anismus, trapping in a rectocele, and intussusception cannot be diagnosed. Because these are the main reasons for investigating difficult defecation, the fluoroscopic examination is the simplest and most reliable method. Endoanal ultrasound is an ideal screening examination for incontinence to show internal sphincter degeneration and tears of the internal or external sphincters. The diagnosis of external sphincter atrophy on ultrasound is not yet resolved, and this remains an important indication for endoanal MR imaging.     

Intrarectal pressures and balloon expulsion related to evacuation proctography.

Seventy four patients with constipation were examined by standard evacuation proctography and then attempted to expel a small, non-deformable rectal balloon, connected to a pressure transducer to measure intrarectal pressure. Simultaneous imaging related the intrarectal position of the balloon to rectal deformity. Inability to expel the balloon was associated proctographically with prolonged evacuation, incomplete evacuation, reduced anal canal diameter, and acute anorectal angulation during evacuation. The presence and size of rectocoele or intussusception was unrelated to voiding of paste or balloon. An independent linear combination of pelvic floor descent and evacuation time on proctography correctly predicted maximum intrarectal pressure in 74% of cases. No patient with both prolonged evacuation and reduced pelvic floor descent on proctography could void the balloon, as maximum intrarectal pressure was reduced in this group. A prolonged evacuation time on proctography, in combination with reduced pelvic floor descent, suggests defecatory disorder may be caused by inability to raise intrarectal pressure. A diagnosis of anismus should not be made on proctography solely on the basis of incomplete/prolonged evacuation, as this may simply reflect inadequate straining.     

Endosonography in anorectal disease: an overview

Anorectal endosonography (AE), which was introduced 20 years ago, derives from the study of urology. It was first used to evaluate rectal tumours and later also to investigate benign disorders of the anal sphincters and pelvic floor. The technique is easy to perform, it has a short learning curve and causes no more discomfort than a routine digital examination. A rotating probe with a 360 degrees radius and a frequency between 5 and 16 MHz is introduced to the rectum and then slowly withdrawn so that the pelvic floor and subsequently the sphincter complex are seen. Recently, it has become possible to reconstruct three-dimensional images. AE has been used for almost every possible disorder in the anal region and has increased our insight into anal pathology. The clinical indications for AE are: 1. Faecal incontinence in patients when surgery is an option. AE can show sphincter defects with excellent precision. There is a perfect correlation with surgical findings. Studies comparing AE with endoanal magnetic resonance imaging (MRI) have shown that both methods are equally good for demonstrating defects in the external anal sphincter; the internal anal sphincter is better visualized with AE. After sphincter repair, the effect is directly related to the decrease in the sphincter defect. 2. Perianal fistulae. AE has been shown to be accurate in staging perianal cryptoglandular fistulae and fistulae in Crohn's disease. When there is an external fistula opening, H2O2 can be introduced with a plastic infusion catheter. The tract then becomes visible as a hyperechoic lesion ("white"). It has been shown that this corresponds well with surgical findings. It is equally sensitive as endoanal MRI. Since recurrent cryptoglandular fistulae are complex in 50% and Crohn's fistula in 75%, it is mandatory to perform AE preoperatively in these patients to avoid missed tracts during surgery and subsequent recurrences. 3. Rectal tumors. In low tubulovillous adenomas or malignant polyps considered removable locally, confirming the local resectability (T0 or T1) is mandatory. Although larger rectal and more advanced tumours can be evaluated with AE, MRI is more sensitive in staging nodal involvement. 4. Anal carcinoma for staging. AE has been shown to stage better than the classical TNM classification for both local extension and prognosis. In conclusion, AE images the internal and external anal sphincter with high accuracy. It is easy to perform and is of particular value in the diagnosis of anal incontinence and perianal fistulae. It is excellent in staging anal carcinoma and can also be used in staging rectal carcinoma, especially very low large malignant polyps.     

Sonographic Characteristics of Rectal Sensations in Healthy Females

Purpose This study was designed to characterize rectal sensations by visualizing the internal and external anal sphincter and intra-anal transport of bolus during elicited rectal sensations. Methods The anal canal was visualized with real-time transperineal ultrasonography in 13 healthy female volunteers. Rectal sensations were elicited by injecting water into the rectum. The ultrasound images were recorded on a videotape and analyzed offline. Results The median time between an injection of water and the events studied was calculated in 105 rectal sensations. A relaxation in the internal anal sphincter (4 seconds after the injection of water), an antegrade transport of bolus (4 seconds) into the anal canal, and a contraction in the external anal sphincter (5 seconds) were observed before a sensation (6 seconds) was reported. The antegrade flow continued until the distal internal anal sphincter contracted (18 seconds) and the bolus moved in a retrograde transport direction (17 seconds) thereafter the sensation disappeared (18 seconds) and the external anal sphincter relaxed (22 seconds). A significant correlation in time between the end of the sensation, contraction in the internal anal sphincter, reversed flow of anal contents, and relaxation of the external anal sphincter was found (Pearson, P<0.01). Conclusions The results verified that the internal anal sphincter contributes to the perception of rectal sensations by a relaxation allowing intra-anal bolus to increase the pressure on the anoderm during rectal contraction. A new observation is presented on the time relation between contraction in the distal internal anal sphincter, reversed flow in the anal canal, and the end of rectal sensations. Presented at the meeting of the International Continence Society, Christchurch, New Zealand, November 27 to December 1, 2006. Supported by Hitachi Ultrasound, Supfstrasse 24, 6300 Zug Switzerland provided the sonography system. Reprints are not available.     

Prospective assessment of the clinical value of anorectal investigations

BACKGROUND/AIM: Anorectal physiological testing and imaging have become part of routine colorectal and gastro-enterological practice, but their clinical value is controversial. We prospectively evaluated the new diagnostic information, impact on management and prognostic information provided by anorectal testing. METHODS: One hundred consecutive patients referred for testing were studied. The referring doctor's diagnosis, reason for referral, planned management and expectation of the value of investigations were recorded. Incontinent patients underwent anorectal physiological testing and endo-anal ultrasound. Patients with constipation underwent anorectal physiological testing and a study of whole-gut transit time to distinguish between slow and normal transit. Constipated patients over age 45, or those younger patients who digitated to assist defaecation, also underwent evacuation proctography to identify large rectoceles. RESULTS: Fifty-one patients had faecal incontinence. Of 12 patients with suspected anterior external anal sphincter obstetric damage, all of whom were planned for surgical repair, 3 were unsuitable for repair, 3 had a normal sphincter, 2 had a weak but structurally intact sphincter, and 1 had internal anal sphincter damage only. Of 6 patients with failed anterior repair, 3 had a defect suitable for repeat repair, 2 had intact repairs and good function, and 1 had extensive damage requiring reconstructive surgery. The tests also influenced management for incontinent patients after haemorrhoidectomy surgery (n = 5), after fistula surgery (n = 5), with congenital abnormalities (n = 3), after cerebrovascular accident (n = 1) and those with no presumptive diagnosis (n = 15). Of the 20 patients referred with constipation, demonstration of a recto-anal reflex in 1 patient with a megarectum excluded the need for full-thickness biopsy. A further patient with altered electrosensation went on to have a neurological lesion defined. Definition of slow transit in some patients did not immediately affect management. New information or a change in management was provided in patients referred for pre-operative assessment (n = 13). Information was gained in only 1 of 7 patients with solitary rectal ulcer and in none of the 8 patients with anal pain. CONCLUSION: Anorectal assessment provides important diagnostic and prognostic information and directly alters management in patients with benign anorectal disorders.     

Endosonographic evidence of injury to the internal anal sphincter after low anterior resection

PURPOSE: Transanal stapled anastomosis has been associated with continence disturbances and reduced postoperative anal sphincter function. The aim of the present work was to study the effect of transanal stapling on anal sphincter morphology by endoanal ultrasound. METHODS: Thirty-nine consecutive patients undergoing stapled low anterior resection for rectal carcinoma were assessed. Each patient was assessed by endoluminal ultrasound before surgery, immediately after surgery, and at 3, 6, 9, 12, and 24 months after surgery. RESULTS: There were no preoperative internal and sphincter defects observed. Three female patients were observed to have preoperative evidence of external anal sphincter defects. After low anterior resection, seven patients were found to have internal anal sphincter defects, which persisted after the two-year follow-up. There were no additional external anal sphincter injuries. Three patients with internal anal sphincter injuries required the use of pads for poor bowel function. CONCLUSIONS: Up to 18 percent of patients who underwent stapled low anterior resection had long-term evidence of internal anal sphincter injury. The external sphincter does not appear to be affected by the procedure.Read at the meeting of The American Society of Colon and Rectal Surgeons, Seattle, Washington, June 9 to 14, 1996.