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.     

Update of tests of colon and rectal structure and function

This review deals with the indications, methods, strengths, and limitations of anorectal testing in clinical practice. In chronic constipation, anal manometry and a rectal balloon expulsion test, occasionally supplemented by defecography, are useful to identify a functional defecatory disorder, because symptoms may respond to pelvic floor retraining. In patients with fecal incontinence, diagnostic testing complements the clinical assessment for evaluating the pathophysiology and guiding management. Manometry measures anal resting and squeeze pressures, which predominantly reflect internal and external anal sphincter function, respectively. Defecation may be indirectly assessed by measuring the recto-anal pressure gradient during straining and by the rectal balloon expulsion test. Endoanal ultrasound and magnetic resonance imaging (MRI) can identify anal sphincter structural pathology, which may be clinically occult, and/or amenable to surgical repair. Only MRI can identify external sphincter atrophy, whereas ultrasound is more sensitive for internal sphincter imaging. By characterizing rectal evacuation and puborectalis contraction, barium defecography may demonstrate an evacuation disorder, excessive perineal descent or a rectocele. Dynamic MRI can provide similar information and also image the bladder and genital organs without radiation exposure. Because the measurement of pudendal nerve latencies suffers from several limitations, anal sphincter electromyography is recommended when neurogenic sphincter weakness is suspected.     

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.     

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.     

Endoanal ultrasonography in fecal incontinence: Current and future perspectives

Fecal incontinence has a profound impact in a patient’s life, impairing quality of life and carrying a substantial economic burden due to health costs. It is an underdiagnosed condition because many affected patients are reluctant to report it and also clinicians are usually not alert to it. Patient evaluation with a detailed clinical history and examination is very important to indicate the type of injury that is present. Endoanal ultrasonography is currently the gold standard for sphincter evaluation in fecal incontinence and is a simple, well-tolerated and non-expensive technique. Most studies revealed 100% sensitivity in identifying sphincter defect. It is better than endoanal magnetic resonance imaging for internal anal sphincter defects, equivalent for the diagnosis of external anal sphincter defects, but with a lower capacity for assessment of atrophy of this sphincter. The most common cause of fecal incontinence is anal sphincter injury related to obstetric trauma. Only a small percentage of women are diagnosed with sphincter tears immediately after vaginal delivery, but endoanal ultrasonography shows that one third of these women have occult sphincter defects. Furthermore, in patients submitted to primary repair of these tears, ultrasound revealed a high frequency of persistent sphincter defects after surgery. Three-dimensional endoanal ultrasonography is currently largely used and accepted for sphincter evaluation in fecal incontinence, improving diagnostic accuracy and our knowledge of physiologic and pathological sphincters alterations. Conversely, there is currently no evidence to support the use of elastography in fecal incontinence evaluation.     

Complex perirectal sepsis: clinical classification and imaging

Background The use of specialized imaging to assess cryptogenic fistula-in-ano is selective, aimed at delineation of the site of the internal fistula opening and the relationship of the primary and secondary tracks and collections to the main levator plate. Advanced imaging also permits definition of the destructive effects of perirectal sepsis (e.g. internal or external anal sphincter damage, perineal body destruction and an ano- or rectovaginal fistula), which may require secondary reconstructive surgery. Methods We performed a PubMed search of outcomes for fistula management in the English and non-English literature, and summarized results regarding the accuracy of internal opening and horseshoe detection as well as the operative correlation for cryptogenic and non-cryptogenic fistula-in-ano using endoanal ultrasound (EAUS) and magnetic resonance (MR) imaging. Only literature defining these characteristics was included. Results The advantages and limitations of the main forms of imaging are discussed in this review with emphasis on EAUS and endoanal or pelvic phased-array MR fistulography. The new technique of transperineal sonography is highlighted. A small but important group of patients with complex fistula-in-ano require specialized imaging. There are specific limitations of endoanal ultrasound (EAUS) which necessitate pelvic phased-array MR imaging. Initial work suggests that EAUS may have a role in intraoperative use for image-guided drainage of recurrent abscesses where operative interpretation can be difficult. The coloproctologist in a tertiary referral center must acquire the skills of ultrasound performance in order to successfully treat fistulous disease, suggesting a role for formal imaging accreditation as part of coloproctological training. Conclusion Future studies should determine both what sequential imaging algorithms for imaging are cost-effective as well as predictive of fistula cure.     

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.     

Dystonie als Ursache einer Outlet-Obstruction

A 36-year-old male presented for treatment of refractory constipation having been present for 15 years. In addition, he gave a history of disturbed micturition. Neurologic findings were a choreoathetoid movement disorder, involving the muscles of the face, tongue, larynx, pharynx and extremities. Involuntary movements were markedly enhanced by any voluntarily initiated movement. This disorder was due to early infantile brain damage. Digital examination of the anal canal revealed spontaneous contractions of the external anal sphincter and puborectalis muscle in rest. Proctological examination was normal except for involuntary sphincteric contractions. Intermittent increase of pressure was seen on manometry. Defecography showed impaired evacuation of the barium enema, small portions only were expelled, and defecation was immediately interrupted again by the involuntarily contractions. Urologically, the patient complained of voiding disorders. The urethral pressure profile showed irregular contractions during micturition. The EMG done with concentric needle electrodes from the external anal sphincter, puborectalis muscle and external vesical sphincter revealed synchronous contractions of these muscles. The EMG was not suggestive of any other central or peripheral neurogenic lesion. In our opinion the involuntary contractions of the striated bladder and anal sphincters in this case (urethrismus, anismus) are a dystonic phenomenon within the context of a generalized choreoathetoid movement disorder. We treated the patient by injecting botulinum toxin, 20 units Botox^® (Allergan. USA) each into the left and right portion of the external anal sphincter and the puborectalis muscle with satisfactory therapeutic response (regular bowel movement) and no fecal incontinence (total 40 units).     

Diagnostic precision of endoanal MRI in the detection of anal sphincter pathology—a meta-analysis

Objective This study aims to evaluate the diagnostic precision of endoanal magnetic resonance imaging in identifying anal sphincter injury and/or atrophy when compared with either endoanal ultrasound or surgical diagnosis. Materials and methods Quantitative meta-analysis was performed on nine studies, comparing endoanal MRI with endoanal ultrasound or surgical diagnosis in 157 patients. Sensitivity, specificity, and diagnostic odds ratio were calculated for each study. Summary receiver operating characteristic curves (SROC) and subgroup analysis were undertaken. Results The overall sensitivity and specificity of endoanal MRI for external sphincter injury was 0.78 (95%CI: 0.66–0.84) and 0.66 (95%CI: 0.51–0.79), respectively. For internal sphincter injury detection, this was 0.63 (95%CI: 0.50–0.74) and 0.71 (95%CI: 0.60–0.81), respectively. For detection of atrophy, this was 0.86 (95%CI: 0.71–0.95) and 0.82 (95%CI: 0.65–0.93), respectively. The area under the SROC curve and diagnostic odds ratio were 0.84 (SE = 0.07) and 6.14 (95%CI: 2.17–17.4) for external sphincter injury, 0.79 (SE = 0.07) and 4.60 (95%CI: 1.75–12.15) for internal sphincter injury, and 0.92 (SE = 0.08) and 21.49 (95%CI: 2.87–160.64) for sphincter atrophy. Conclusion Endoanal MRI was sensitive and specific for the detection of external sphincter injury and especially sphincter atrophy. It may be useful as an alternative to endoanal ultrasound in patients presenting with fecal incontinence, although further clinical studies are needed to identify its best application in clinical practice.     

Dynamic MR imaging of outlet obstruction

The outlet obstruction syndrome encompasses all pelvic floor abnormalities which are responsible for an incomplete evacuation of fecal contents from the rectum. It has been estimated that outlet obstruction may be observed in half of constipated patients. A detailed clinical examination still represents the cornerstone of the diagnosis of these patients. However, there is general agreement that a reliable evaluation of the different pelvic floor abnormalities and the treatment decision highly depend on the imaging assessment. Traditionally, conventional defecography has played an important role in the radiological assessment of these patients but the technique is limited by its projectional nature and its inability to detect soft-tissue structures. Dynamic pelvic MR imaging using either closed-configuration or open-configuration MR systems is a rapidly evolving technique which has been gaining increased interest over the last years. The free selection of imaging planes, the good temporal resolution, and the excellent soft-tissue contrast have transformed this method into the preferred imaging modality in the evaluation of patients with pelvic floor dysfunction including rectocele, enterocele, internal rectal prolapse, and anismus.     

Funktionsdiagnostik des Kolons und Anorektums

For evaluation of functional disturbances of the colon and anorectum, diagnostic methods are available for measurement of motor activity, anorectal sensory function and evacuation. Measurement of motor activity can be achieved by colon (mostly after colonoscopic cleaning) and anorectal manometry or by barostat measurements. Anorectal manometry and barostat measurements also enable investigation of the colorectal sensory function. Intraluminal transit can be assessed with scintigraphy or by ingestion of radiopaque markers. Defecography either by conventional X-ray or magnetic resonance imaging (MRI) can be used to visualize defecation disorders. From a clinical point of view, functional disturbances of the colon and anorectum manifest themselves as chronic constipation, including defecation disorders and fecal incontinence. Both syndromes are characterized by a high prevalence and a severely disturbed quality of life. Diagnostic evaluation should be initiated if a trial therapy fails. Colonic transit time measurement, defecography, and anorectal manometry are indicated for evaluation of chronic constipation, while anorectal manometry, anal endoscopic ultrasound, sphincter electromyogram (EMG), and if necessary, investigation of diarrhea are required for fecal incontinence.     

Electromyography of the external anal sphincter

PURPOSE: Electromyography of the external anal sphincter is frequently used when investigating patients with defecation disorders. Investigations are often performed using an invasive technique by perineal insertion of a needle or wire electrode. The aim of the present study was to investigate whether surface electromyography, with electrodes applied to the perineal skin, is a reliable method in the diagnosis of paradoxical anal sphincter reaction. METHODS: Seventy-one patients with defecation disorders participated in the present study. They were investigated with electromyography of the external anal sphincter using surface and needle electrodes. RESULTS: In 65 of 71 (92 percent) patients the electromyography recording showed the same result during straining using surface electrodes when compared with needle electrodes. Twenty-two of these 65 patients had paradoxical anal sphincter reaction, and 43 patients had decreased electromyography activity. In 6 of 71 (8 percent) patients the electromyography recording showed a different pattern during straining using surface electrodes when compared with needle electrodes. CONCLUSION: The present study demonstrates a good correlation between surface electrodes applied to the perineal skin and concentric needle electrodes in the diagnosis of paradoxical anal sphincter reaction. Noninvasive electromyography recordings of the external anal sphincter are often preferred in the diagnosis of paradoxical anal sphincter reaction.Supported by grants from Kjell and Märta Beijers Stiftelse, Marianne and Marcus Wallenbergs Stiftelse, Bert von Kantzow's Research Foundation, and Karolinska Institutet Research Funds.     

Diagnostic approach to faecal incontinence: What test and when to perform?

Faecal incontinence (FI) is a debilitating common end result of several diseases affecting the quality of life and leading to patient disability, morbidity, and increased societal burden. Given the various causes of FI, it is important to assess and identify the underlying pathomechanisms. Several investigatory tools are available including high-resolution anorectal manometry, transrectal ultrasound, magnetic resonance imaging, and electromyography. This review article provides an overview on the causes and pathophysiology of FI and the author’s perspective of the stepwise investigation of patients with FI based on the available literature. Overall, high-resolution anorectal manometry should be the first investigatory tool for FI, followed by either transrectal ultrasound or magnetic resonance imaging for anal internal sphincter and external anal sphincter injury, respectively.     

Effects of biofeedback on obstructive defecation--reconditioning of the defecation reflex?

Twenty two patients with obstructive defecation were recruited for relaxation training by domiciliary self regulatory biofeedback. Each patient served as his or her own control for anorectal and proctographic assessments. Biofeedback training improved the obstructive symptoms of the patients and showed significant change in various parameters related to the obstructive defecation syndrome. As examined by isotope dynamic proctography: the defecation rate (% of evacuation/defecation time) was significantly increased (p < 0.05), the anorectal angles at rest and during attempted defecation were made more obtuse (p < 0.05), and the pelvic floor movements were made more dynamic on voluntary contraction of the anal sphincter (p < 0.03). The external anal sphincter electromyographic voltage recorded during defecation was significantly reduced (p < 0.0005) as was the surface anal plug electromyographic electrode voltage (p < 0.0001), which was associated with a greatly reduced anismus index (p < 0.0001). The rectal sensation was improved (p < 0.05), concomitantly. Biofeedback thus improves the defecation act in patients suffering from inappropriate contraction of the pelvic floor and sphincter musculature. Furthermore, this study has shown that biofeedback objectively influences the defecation reflex leading to an improved quality of higher control of bowel function.     

A new concept of the anatomy of the anal sphincter mechanism and the physiology of defecation

The role of the external and internal anal sphincters in the mechanism of anal continence is presented. The external sphincter induces continence by 1) preventing internal sphincter relaxation, what I have called the “voluntary inhibition action,” and 2) mechanical compression of the rectal neck and anal canal proper. The mechanism of both actions is described. The internal sphincter plays a significant role not only in involuntary, but also in voluntary, continence. The importance of this role in the correction of anal incontinence is clarified. “Stress defecation,” a condition which follows internal sphincter damage, is discussed. A “single loop continence” theory is presented, based on the fact that each of the three loops of the external sphincter has its own innervation, attachment, and direction of muscle bundles; each loop thus acts as a separate sphincter. The clinical application of this theory is presented.     

Correlation of endoanal sonography with cross-sectional anatomy of the anal sphincter

BACKGROUND: Anal endosonography has become an important imaging method in the diagnosis of anorectal disorders. However, little information exists as to whether anal endosonography reliably defines pelvic floor structures. The aim of this study was to correlate endoanal sonography with cross-sectional anatomy and histology. METHODS: Endosonographic tomograms were obtained from 9 human cadavers before fixation and cross-sectioning at identical levels. Muscular layers were defined by visual inspection, histology, immunohistology, and morphometry using three-dimensional sphincter reconstructions. RESULTS: Endosonography visualized only two muscular layers, whereas anatomic sections always revealed three. Comparisons revealed identical findings with regard to internal sphincter volumes and asymmetries. However, due to its failure to identify the longitudinal muscle, endosonography largely overestimated external sphincter volumes. In contrast to current beliefs, anatomic studies failed to detect striated muscle fibers within the longitudinal muscle and did not show an intersphincteric space. However, anatomic cross sections demonstrated "anterior bands" as newly described anchoring mechanisms for the anal sphincters. CONCLUSIONS: Anal endosonography supplies accurate information with regard to internal anal sphincter dimensions, but does not reliably outline deeper muscular layers. However, despite these drawbacks, comparisons of modern imaging techniques with cross-sectional anatomy may enhance our understanding of pelvic floor anatomy.     

Outlet obstruction constipation (anismus) managed by biofeedback.

Fifteen subjects presenting with intractable constipation due to obstructive defecation, mean (SEM) duration 8.8 (1.8) years, had the inappropriate contraction and electromyographic changes in the pelvic floor muscles and external and sphincter typical of this condition. An electromyographically derived index was used to grade its severity. A self applied biofeedback device was used to allow electromyographic recording of the abnormal external anal sphincter. The subjects were encouraged to reduce the abnormal electromyographic activity on straining after instruction and training. The procedure was intended as a relearning process in which the non-relaxing activity of the pelvic floor was gradually suppressed. Biofeedback training was maintained on a domiciliary basis for a mean time of 3.1 weeks and resulted in a significant reduction in the anismus index (mean (SEM) 69.9 (7.8)% before biofeedback, mean 14 (3.9)% after biofeedback, p less than 0.01). There was an associated reduction in the time spent straining at stool and in the difficulty of defecation and an increased frequency of defecation. Defecatory video proctograms in six subjects showed improvements in the anorectal angle during straining and evacuation. The clinical benefit to the patients persisted after a mean follow up of 6.2 months.     

Cooperative Roles of Colon and Anorectum During Spontaneous Defecation in Conscious Dogs

Colorectal motility during spontaneous defecation was investigated using force strain gauge transducers implanted in the proximal colon, distal colon, rectum, and anus in six dogs. One 24-hr recording and several defecation recordings were made in each dog. During 24-hr recordings, 29 giant contractions were observed in the distal colon. The giant contractions, which propagated to the rectum, accompanied evacuation more frequently than those that stopped at the distal colon (P < 0.05). Of 66 episodes of defecation, 63 (95%) were accompanied by a giant contraction of the distal colon. Of these, 57 (90%) propagated to the rectum. In three events, giant contraction originated at the rectum. The rectum relaxed prior to the contraction. The internal anal sphincter also relaxed. Migration of giant contraction to the rectum, rectal relaxation-contraction sequence and sphincter relaxation played important roles during defecation. Defecation is a consequence of successive phenomena occurring in both the colon and anorectum.     

Rektozele

Anterior rectocele is a common morphological condition in patients with obstructive defecation syndrome. Typical symptoms include incomplete evacuation, transanal or transvaginal digitation and soiling, which is frequently interpreted as fecal incontinence. Diagnosis of rectocele is made clinically and functional assessment of rectocele can be performed by dynamic imaging, e.g. by magnetic resonance (MR) defecography. Primary treatment should be conservative. Concerning surgical treatment, transanal, transperineal, transvaginal and transabdominal procedures are available. Evidence-based guidelines for surgical treatment are still lacking. The question whether rectocele is a cause or a consequence of obstructive defecation syndrome remains controversial. Accordingly, indications for surgical correction of rectocele should be considered with caution.     

Are special investigations of value in the management of patients with fecal incontinence?

PURPOSE: The aim of this study was to determine whether special investigations significantly alter either the diagnosis or the management plan of patients with fecal incontinence assessed on the basis of a structured history and physical examination alone. METHODS: Fifty consecutive patients with fecal incontinence were prospectively studied in a tertiary referral clinic. Each patient was assessed by two clinicians who independently formulated a diagnosis and treatment plan based on the history and physical examination. The resulting 100 patient assessments were then compared with the final diagnosis and treatment plan formulated on completion of endoanal ultrasound, anal manometry, external sphincter electromyography, and defecating proctography. RESULTS: In the assessment of fecal incontinence, the addition of special investigations altered the diagnosis of the cause of incontinence based on history and examination alone in 19 percent of cases. The management plan was altered in 16 percent of cases. Special investigations were most useful in separating neuropathy from rectal wall disorders and in demonstrating the unexpected presence of internal sphincter defects and neuropathy. CONCLUSIONS: Even experienced colorectal surgeons will misdiagnose up to one-fifth of patients presenting with fecal incontinence if assessment is based on the history and physical examination alone. However surgically correctable causes of incontinence are rarely missed on clinical assessment.