Assessment of external anal sphincter morphology in idiopathic fecal incontinence with endocoil magnetic resonance imaging

The failure of external anal sphincter repair may relate to sphincter atrophy where muscle fibers are replaced by fat, seen on MRI due to the differing signals returned by fat and muscle tissue. Manometry, electrophysiology, and MRI with an endocoil were performed on 34 fecally incontinent patients with intact sphincters on endosonography. The area of the external sphincter was measured in the midcoronal plane, and the percentage fat content calculated. Sphincter muscle area correlated strongly with squeeze pressure (P < 0.001) but not with percentage fat content. There was no relationship between percentage fat and age, weight, anal sensation, squeeze pressure, sphincter length or width, or pudendal nerve terminal motor latency. There was a trend for smaller sphincters to contain a higher percentage fat content (P = 0.059). MRI has established a relationship between function and external sphincter bulk, but not fat content, although smaller muscles may contain more fat.     

Transanal endoscopic microsurgery excision: is anorectal function compromised?

PURPOSE: Transanal endoscopic microsurgery is a new technique that has not yet found its place in routine practice. The procedure results in dilation of the anal sphincter with a large-diameter operating sigmoidoscope, sometimes for a prolonged period. The purpose of the present study was to assess the effect of transanal endoscopic microsurgery on anorectal function. METHODS: Eighteen consecutive patients undergoing transanal endoscopic microsurgery excision of rectal tumors, of whom 13 were available for evaluation, were included. Continence was scored by a numeric scale before surgery and at three and six weeks after surgery. Anorectal physiology studies were performed preoperatively and six weeks postoperatively with manometry, pudendal nerve motor terminal latency, anal mucosal electrosensitivity, rectal balloon volume studies, and endoanal ultrasound. RESULTS: There was a significant reduction in mean anal resting pressure (104 ± 32 cm H2O before surgery, 73 ± 30 cm H2O after surgery; P = 0.0009). There was no significant change in squeeze or cough pressure, pudendal nerve terminal motor latency, anal mucosal electrosensitivity, or rectal balloon study volumes. Fall in resting pressure was significantly correlated with length of operating time (r2 =0.39, P = 0.047). There was no significant change in mean continence score after surgery. CONCLUSION: Transanal endoscopic microsurgery results in a reduction in internal sphincter tone. This did not affect continence in a short-term study.     

Delayed pudendal nerve conduction and endosonographic appearance of the anal sphincter complex

PURPOSE: The aim of this study was to test the hypothesis that a delay in pudendal nerve conduction as measured by pudendal nerve terminal motor latency should be associated with atrophy of the external anal sphincter as measured using endoanal ultrasound. METHODS: Sixty-two adult females (median age, 58.9 (range, 22–88) years) presenting for evaluation of fecal incontinence with no evidence of an external anal sphincter tear on ultrasound were recruited. Ultrasound was performed with a 7.5-MHz radial rotating axial endoprobe in the left lateral position. Four measurements were made in the transverse plane—the external anal sphincter thickness in the midanal canal at the 6 o'clock and 9 o'clock positions, the internal sphincter at the 9 o'clock position, and the external anal sphincter in the low canal at the 9 o'clock position. Pudendal nerve terminal motor latency was measured using a transrectal nerve stimulation technique with measurement of the evoked muscle response. RESULTS: Although there was a trend toward thinner external sphincter muscles in those with bilateral prolonged pudendal nerve terminal motor latency, independent sample t-tests and Pearson correlation coefficients showed no statistically significant relationship (right pudendal nerve terminal motor latency:P=0.083, 0.184, 0.128, 0.910;r=0.228, 0.175, –0.201, –0.015; left pudendal nerve terminal motor latency:P=0.946, 0.276, 0.510, 0.123;r=–0.009, –0.143, –0.087, –0.201). CONCLUSIONS: No statistically significant relationship between ultrasound-measured anal sphincter muscle thickness and pudendal nerve terminal motor latency was identified. Although a trend was suggested that could be further evaluated by a study with a larger sample size and a control group with asymptomatic patients, the small differences in muscle thickness involved and the difficulties in measurement suggest that the establishment of clinically useful ultrasound criteria for the detection of the neuropathic anal sphincter complex is unlikely.     

The relationship of pudendal nerve terminal motor latency to squeeze pressure in patients with idiopathic fecal incontinence

PURPOSE: With the advent of transanal ultrasonography it has been possible to identify those incontinent patients without sphincter defects. The majority of these patients are now thought to have neurogenic fecal incontinence secondary to pudendal neuropathy. They have been found to have reduced anal sphincter pressures and increased pudendal nerve terminal motor latencies. The aim of this study was to determine whether in those incontinent patients who do not have a sphincter defect, prolonged pudendal nerve terminal motor latency correlates with anal manometry, in particular maximum squeeze pressure. METHODS: Sixty-six incontinent patients were studied with transanal ultrasonography, anorectal manometry, and pudendal nerve terminal motor latency. Twenty-seven continent controls had anorectal manometry and pudendal nerve terminal motor latency measured. RESULTS: Maximum resting pressure and maximum squeeze pressure were significantly lower in the group of incontinent patients with bilateral prolonged pudendal nerve terminal motor latency (median maximum resting pressure = 26.5 mmHg; median maximum squeeze pressure = 60 mmHg) when compared with incontinent patients with normal bilateral pudendal nerve terminal motor latencies (median maximum resting pressure = 46 mmHg; median maximum squeeze pressure = 79 mmHg; maximum resting pressure P = 0.004; and maximum squeeze pressure P = 0.04). In incontinent patients with no sphincter defects no correlation between pudendal nerve terminal motor latency and maximum squeeze pressure was found (r = -0.109, P = 0.48) and maximum squeeze pressure did not correlate with bilateral or unilateral prolonged pudendal nerve terminal motor latency (r = -0.148, P = 0.56 and r = 0.355, P = 0.19 respectively). CONCLUSIONS: In patients with idiopathic fecal incontinence damage to the pelvic floor is more complex than damage to the pudendal nerve alone. Although increased pudendal nerve terminal motor latency may indicate that neuropathy is present, in patients with neuropathic fecal incontinence, pudendal nerve terminal motor latency does not correlate with maximum squeeze pressure. Normal pudendal nerve terminal motor latency does not exclude weakness of the pelvic floor.     

Anal endosonography: Relationship with anal manometry and neurophysiologic tests

Thirty-seven patients were referred for evaluation of anal function; their clinical diagnoses were traumatic fecal incontinence (13), idiopathic (pudendal neuropathy) fecal incontinence (7), fecal soiling (9), and other (8). In all patients, anal endosonography (sphincter defects and internal sphincter thickness [IST]) and anal manometry (maximal basal pressure [MBP] and maximal squeeze pressure [MSP]) were performed. In 18 patients, neurophysiologic tests (EMG-maximal contraction pattern [MCP], single-fiber EMG [fiber density; FD], and pudendal nerve terminal motor latency [PNTML]) were also performed. Endosonography demonstrated in seven patients both an internal and external sphincter defect (Group 1), in seven patients an internal sphincter defect and in one patient an external sphincter defect (Group 2), and in 22 patients no sphincter defect (Group 3). There was a significant difference among these three groups for MBP and MCP, the lowest being in Group 1. Between the patients with traumatic fecal incontinence and idiopathic fecal incontinence, no differences in IST, MBP, MSP, MCP, FD, and PNTML were found. In two patients with a suspected obstetric trauma, there was an unexpected additional severe pudendal neuropathy. In one patient with a suspected obstetric trauma, no damage of the anal sphincters could be demonstrated. In one patient with suspected idiopathic fecal incontinence, there was an additional, unsuspected defect of the internal sphincter. There was concordance between endosonography and EMG in the mapping of the external sphincter. Clinical diagnoses can be misleading in differentiating between traumatic and idiopathic fecal incontinence; anal endosonography provides unsuspected and additional information about the sphincters; PNTML can reveal unsuspected neuropathy in traumatic fecal incontinence. Therefore, the combination of endosonography and PNTML is promising in selecting patients for surgery.     

Sonographic,manometric, and myographic evaluation of the anal sphincters morphology and function

PURPOSE: A direct comparison of anal sphincter physiology (muscle performance and anatomy-muscle thickness) has not yet been undertaken but may be of importance in patients with defecation disorders. METHODS: We evaluated 15 healthy volunteers by means of anorectal manometry to determine pressure functions of the internal and external anal sphincter. Transcutaneous electromyography was recorded to assess the electrical activity of the external anal sphincter. Thickness of the anal sphincter muscles was measured sonographically from within the anal canal with dorsal projection using a 7.5-MHz 360° rectal panorama scanner. RESULTS: It was shown that neither is the muscle thickness of the external anal sphincter during rest (6.26±1.02 mm) or during squeezing (7.40±1.39 mm) correlated to its squeeze pressure (138.8±15.2 mmHg), nor is the diameter of the internal anal sphincter (2.09±0.58 mm) correlated to its resting pressure (61.1±15.2 mmHg). Finally, the thicker the internal anal sphincter muscle, the lower the electrical activity of the external anal sphincter during squeezing (r=0.74,P <0.001). CONCLUSION: It is concluded that both manometry to assess sphincter function and sonography to determine sphincter morphology are important measures in the evaluation of continence function.     

Anal function in geriatric patients with faecal incontinence.

The association of faecal incontinence with constipation and confusion in the elderly is well recognised but the anal function of faecally incontinent geriatric patients is poorly understood. Anal studies were therefore performed on 99 geriatric patients (49 with faecal incontinence, 19 continent patients with faecal impaction and 31 geriatric control patients with normal bowel habit) and 57 younger healthy control patients. An age related reduction in anal squeeze pressure but not resting pressure was identified. A reduction in anal resting pressure was detected in the faecally incontinent geriatric patients but squeeze pressure did not differ significantly from that found in the other geriatric patients. Anal sensation was impaired in the faecally incontinent patients. No difference was found between the groups as measured by pudendal nerve terminal motor latency. Gross neuropathy of the distal part of the pudendal nerve does not account for the observed external anal sphincter weakness in geriatric patients or for their faecal incontinence. Internal anal sphincter dysfunction is an important factor in faecal incontinence in the elderly.     

Fistula-in-ano

The functional outcome of fistula surgery can be quantitated by anal manometry. A closed, water-filled microballoon (0.5 X 1.0 cm) system was used to measure resting anal pressure and maximal squeeze pressure in 47 patients with anal fistulas at St. Mark's Hospital. After treatment of intersphincteric fistulas, there was a significant reduction in resting pressure in the distal 2 cm. In treated transphincteric fistulas and suprasphincteric fistulas, anal pressure was reduced in the distal 3 cm. A significant lower pressure was measured in patients having the external sphincter divided, compared with those having the muscle preserved. Disturbance of continence was related to abnormally low resting pressure in six patients. This study supports attempts at sphincter preservation in fistula surgery.     

Pudendal neuropathy and severity of incontinence but not presence of an anal sphincter defect may determine the response to biofeedback therapy in fecal incontinence

PURPOSE: It has been suggested that the severity of fecal incontinence, the presence of pudendal neuropathy, or an external anal sphincter defect does not preclude clinical improvement with biofeedback therapy. A discrepancy, however, is frequently found between subjective improvement and objective results after biofeedback therapy. Our aim was to assess whether severity of fecal incontinence, presence of pudendal neuropathy, or an external anal sphincter defect could influence the results of manometric parameters after biofeedback therapy in patients with fecal incontinence. METHODS: Biofeedback therapy was used to treat 27 patients with fecal incontinence (25 women; mean age, 53; range, 29–74 years), according to a strict protocol. Manometry, pudendal nerve terminal motor latency, and anal ultrasound were performed in all patients before biofeedback therapy. Manometric evaluation of external anal sphincter function was performed after the biofeedback sessions. RESULTS: Eight of 27 patients had a good clinical response to biofeedback, but with no significant difference in their mean amplitude and duration of squeeze pressure before and after biofeedback. There was no relationship between the clinical results of biofeedback therapy and the initial severity of fecal incontinence, pudendal neuropathy, or external sphincter defect. Patients with severe incontinence (incontinence to solids) and pudendal neuropathy failed to improve the amplitude and duration of their maximum voluntary contraction after biofeedback therapy. Patients with mild fecal incontinence (incontinence to flatus, liquids, or both) (P<0.04), without pudendal neuropathy (P<0.02), or with (P<0.05) and without (P<0.05) external sphincter defect improved their external anal sphincter function after biofeedback therapy. CONCLUSION: In patients with fecal incontinence, the severity of symptoms and pudendal neuropathy should be considered as two factors of poor prognosis of favorable manometric results after biofeedback therapy. Improvement, on the other hand, may be expected after biofeedback therapy despite an external anal sphincter defect.Presented at the XXIst congress of the Societé Internationale Francophone d'Urodynamique, Lisbon, Portugal, May 14 to 16, 1998.     

The Utility of Pudendal Nerve Terminal Motor Latencies in Idiopathic Incontinence

Purpose Pudendal nerve terminal motor latency testing has been used to test for pudendal neuropathy, but its value remains controversial. We sought to clarify the relationship of pudendal nerve terminal motor latency to sphincter pressure and level of continence in a cohort of patients with intact anal sphincters and normal pelvic floor anatomy. Methods We reviewed 1,404 consecutive patients who were evaluated at our pelvic floor laboratory for fecal incontinence. From this group, 83 patients had intact anal sphincters on ultrasound and did not have internal or external rectal prolapse during defecography. These patients were evaluated by pudendal nerve terminal motor latency testing, a standardized questionnaire, and anorectal manometry, which measured resting and squeeze anal pressures. Incontinence scores were calculated by using the American Medical Systems Fecal Incontinence Score. Values were compared by using the Fisher’s exact test and Wilcoxon’s rank-sum test; and significance was assigned at the P < 0.05 level. Results 1) Using a 2.2-ms threshold, 28 percent of patients had prolonged pudendal nerve terminal motor latency unilaterally and 12 percent bilaterally. 2) At a 2.4-ms threshold, 18 percent of patients had prolonged pudendal nerve terminal motor latency unilaterally and 8 percent bilaterally. 3) Bilaterally prolonged pudendal nerve terminal motor latency was significantly associated with decreased maximum mean resting pressure and increased Fecal Incontinence Score, but not decreased maximum mean squeeze pressure, at both 2.2-ms and 2.4-ms thresholds. 4) Unilaterally prolonged pudendal nerve terminal motor latency was not associated with maximum mean resting pressure, maximum mean squeeze pressure, or fecal incontinence score at either threshold. Conclusions The majority of incontinent patients with intact sphincters have normal pudendal nerve terminal motor latency. Bilaterally but not unilaterally prolonged pudendal nerve terminal motor latency is associated with poorer function and physiology in the incontinent patient with an intact sphincter. Presented at the meeting of The American Society of Colon and Rectal Surgeons, Dallas, Texas, May 8 to 13, 2004. Reprints are not available.     

Fatigability of the External Anal Sphincter in Anal Incontinence

INTRODUCTION Anal incontinence commonly results from external anal sphincter dysfunction. The muscle is routinely assessed by anorectal physiology studies. Fatigability is not routinely measured but should be an important factor in the maintenance of continence. The fatigue rate index has been developed to address this. The purpose of this study was to investigate the fatigability of the external anal sphincter in incontinent patients compared with that in controls and to determine its correlation with symptom severity and pudendal nerve terminal motor latency measurement.METHODS Forty-two patients with anal incontinence (33 female, 9 male) and 20 control patients (17 female, 3 male) were studied. As part of anorectal physiology studies, manometry was measured by a station pull-through technique with a closed-system microballoon. After a rest period of one minute, fatigue was measured over a 20-second squeeze at 1.5 cm in the anal canal with two consecutive readings separated by a further one-minute rest period. The fatigue rate index was calculated from the maximum squeeze pressure and fatigue rate. A validated symptom severity scoring system was used to assess symptomatology in patients with anal incontinence.RESULTS No difference was detected in demographic factors between the two groups. The fatigue rate index was significantly different between the control and incontinent groups (1.85 vs. 0.67 minutes, P = 0.001). No other factors were significantly different between the two groups (maximum squeeze pressure, 89.1 vs. 79 cm H₂O, P = 0.42; fatigue rate, –85.8 vs. –101.2 cm H₂O/min, P = 0.62). The fatigue rate index demonstrated a significant correlation with symptom score (r = –0.44, P = 0.005). The fatigue rate index did not correlate with latency measurement.CONCLUSIONs A significant difference was detected in the fatigue rate index between incontinent and control patients. The Fatigue Rate Index demonstrated a significant correlation with symptom severity score and it may be a useful discriminating measure of external anal sphincter function.Poster presentation at the meeting of The American Society of Colon and Rectal Surgeons, Chicago, Illinois, June 3 to 8, 2002, and at the meeting of the Association of Coloproctology of Great Britain and Ireland, Harrogate, United Kingdom, July 2 to 5, 2002.     

Endoanal ultrasound assessment of sphincter defects and thinning – Correlation with anal manometry

Background and study aimsThis study aims to determine if anal sphincter defects/thinning observed at endoanal ultrasound correlates with anal pressures recorded at anal manometry.Patients and methodsA total of 30 consecutive patients with history suggestive of anal sphincter pathology underwent anal endosonography with documentation of internal and external sphincter defects/thinning. The same patients underwent anal manometry with documentation of maximum resting and maximum squeeze pressures. Patients with a sphincter defect (SD) were compared to patients without a sphincter defect (NSD) and both groups were compared with respect to findings in manometry. The Mann–Whitney U test was used for statistical analysis. This study was approved by the Institutional Ethics Committee.ResultsA statistically significant correlation was found between decreased maximal resting pressure and decreased internal anal sphincter (IAS) thickness or an IAS defect. The correlation between MSP and external sphincter pathology was significantly less consistent in our study.ConclusionOur study showed a statistically significant correlation between maximum resting pressure and observation of internal sphincter defects at endoanal ultrasound. The patients with documented internal sphincter defects have significantly reduced maximum resting pressures. There was however, no correlation between external sphincter defects and decrease in maximum squeeze pressure as has been observed in other studies. Until a manometry cut-off can be set to discriminate between the absence and presence of defects, both manometry and ultrasound should be offered to patients with history suggesting anal sphincter pathology.     

Effects of aging on the anorectal sphincters and their innervation

The effects of aging on the pelvic floor musculature and its innervation are described in 102 women and 19 men without colorectal or pelvic floor disease. In the women, a reduction in anorectal “squeeze” pressure was found in the fifth decade, but the resting anal pressure remained unchanged. This reduction in squeeze anal pressure was accompanied by an increase in the mean pudendal nerve terminal motor latency, indicating damage to this nerve, and increased perineal descent in the resting and straining positions. The fiber density, recorded by single fiber electromyography in the external anal sphincter muscle, a muscle innervated by the pudendal nerves, was increased in the sixth decade, indicating the later development of compensatory reinnervation in this muscle. The interrelation of aging, menopausal effects, and parity in these changes is difficult to define from currently available data, but the authors suggest, from other evidence, that menopausal effects may be relevant. Reprints will not be available.     

Manometric squeeze pressure difference parallels functional outcome after overlapping sphincter reconstruction

PURPOSE: This study was designed to evaluate the effectiveness of overlapping anal sphincter reconstruction and to determine the manometric parameters that correlate with a successful functional outcome. METHODS: A retrospective review of patients who had undergone overlapping sphincter reconstruction for anal incontinence from 1988 to 1999 was undertaken. Only patients with preoperative and six-months-postoperative anal manometry were included in this study. Standard statistical tests were used to compare pre- and postoperative findings. RESULTS: A total of 52 overlapping sphincter reconstructions were performed on 49 patients (46 females). The mean age was 44 (± standard error, 15.8; range, 20–81) years, with follow-up at six months. Forty-two patients had a history of complicated vaginal delivery (episiotomies, tears, forceps delivery); 36 patients had a history of anal or perineal surgery; and two patients had perianal Crohn's disease. Nine patients (17 percent) had undergone prior sphincter repair. Incontinence grade improved in 37 patients (71 percent), and complete continence returned in 21 patients (40 percent). The presence of a rectovaginal fistula, postoperative complications, previous sphincter repair, and increase in pudendal nerve terminal motor latency did not affect functional outcome (P = not significant). Patients older than 50 years had a better functional outcome than their younger counterparts after sphincter repair (P=0.02). Although mean maximal squeeze pressure and mean anal sphincter length increased significantly after sphincter reconstruction (P=0.0006 and 0.004, respectively), only squeeze pressure difference correlated with functional outcome (r=0.37;P=0.007). CONCLUSIONS: Overlapping sphincter reconstruction improved anal function in the majority of patients. The most important factor in the return to normal sphincter function is an increase in squeeze pressure.     

Endosonography in the evaluation of anal function after primary repair of a third-degree obstetric tear

BACKGROUND: Disruption of the anal sphincter occurs in 0.6%-6% of women during delivery and almost half have persistent defecatory symptoms despite primary repair. Our aim was to prospectively analyse anal endosonography and rectoanal manometry after primary repair of a third-degree obstetric tear in order to compare the findings with the clinical outcome. METHODS: Twenty-one women aged 27-41 (mean 31.5 years) who had undergone primary suture of a third-degree disruption of the anal sphincter were interviewed on their pelvic floor function and explored by manometry and endosonography 4 months after delivery. RESULTS: Twelve women had anal incontinence. External sphincter defect was identified on endosonography in 22% continent and in 91% incontinent women (P < 0.01). The presence of an external sphincter defect was associated with anal incontinence in 91.7%. Surgical repair was identified on endosonography in 88% continent women and in 25% incontinent women (P < 0.03). The combination of a visible surgical repair and absence of defect was highly associated with normal continence (91.7%). Squeezing pressures were higher in continent women (87 +/- 23 cm H2O) than in incontinent women (48 +/- 36 cm H2O; P = 0.04), but no anal pressure threshold could achieve better results than endosonography in predicting the clinical outcome. CONCLUSION: After primary repair of a third-degree obstetric tear, endosonographic pattern of the anal sphincter correlates with the continence status.     

Relationship Between External Anal Sphincter Atrophy at Endoanal Magnetic Resonance Imaging and Clinical, Functional, and Anatomic Characteristics in Patients With Fecal Incontinence

Purpose External anal sphincter atrophy at endoanal magnetic resonance imaging has been associated with poor outcome of anal sphincter repair. We studied the relationship between external anal sphincter atrophy on endoanal magnetic resonance imaging and clinical, functional, and anatomic characteristics in patients with fecal incontinence. Methods In 200 patients (mean Vaizey score, 18 (±2.9 standard deviation)) magnetic resonance images were evaluated for external anal sphincter atrophy (none, mild, or severe) by radiologists blinded to anorectal functional test results and details from medical history. Subgroups of patients with and without atrophy were compared for medical history, anal manometry, pudendal nerve latency testing, anal sensitivity testing, external anal sphincter thickness, and external anal sphincter defects. Whenever significant differences were detected, we tested for differences between patients with mild and severe atrophy. Results External anal sphincter atrophy was demonstrated in 123 patients (62 percent): graded as mild in 79 (40 percent), and severe in 44 patients (22 percent). Patients with atrophy were more often female (P < 0.001) and older (P = 0.003). They had a lower maximal squeeze (P = 0.01) and squeeze increment pressure (P < 0.001). Patients with severe atrophy had a lower maximal squeeze (P = 0.003) and squeeze increment pressure (P < 0.001) than patients with mild atrophy. These effects were not attenuated by potential confounding variables. Patients with atrophy could not be identified a priori by other characteristics. Conclusions External anal sphincter atrophy at endoanal magnetic resonance imaging was depicted in 62 percent of patients, varying from mild to severe. Because increasing levels of atrophy were associated with impaired squeeze function, further studies are needed to evaluate whether grading atrophy is clinically valuable in selecting patients for anal sphincter repair. Supported by grant 945-01-013 of the Netherlands Organization for Health Research and Development. Presented in part at the scientific assembly and meeting of the Radiologic Society of North America, Chicago, Illinois, November 27 to December 2, 2005. Reprints are not available.     

Muscle change after anal sphincter reinnervation by a normal somatic peripheral nerve

INTRODUCTION: Pudendal neuropathy causes idiopathic fecal incontinence. We thus designed a new operation for idiopathic fecal incontinence based on the hypothesis that a conversion from innervation by the neuropathic pudendal nerve to that by the normal somatic peripheral nerve innervating a larger skeletal muscle might enable the anal sphincter to recover from neuropathic muscular atrophy. This study was undertaken to investigate the muscular change of the external anal sphincter after such an operation. METHODS: On 14 sides of eight dogs, the transected proximal end of the nerve innervating the biceps femoris muscle was microsurgically cross-transferred to the distal end of the transected pudendal nerve. The external anal sphincter was analyzed by electromyography and adenosine 5'-triphosphatase staining at three months after surgery. RESULTS: On 13 of 14 sides, the external anal sphincter was well preserved and the evoked potential was clearly recorded. The external anal sphincter in these dogs, however, had neither any basal electrical activity nor any increased electrical activity. The percentage of Type 1 muscle fibers of the external anal sphincter innervated by the nerve to the biceps femoris muscle (30.9 +/- 9.8 percent) was significantly higher than that of the normal external anal sphincter (15.2 +/- 8.5 percent; P < 0.001) and also significantly lower than that of the normal biceps femoris muscle (38.5 +/- 7.5 percent; P = 0.006). The diameter of the muscle fibers (Types 1 and 2) of the external anal sphincter (expressed as mean +/- standard deviation) innervated by the nerve to the biceps femoris muscle (32.9 +/- 6.2 microm) was also significantly larger than that of the normal external anal sphincter (29.9 +/- 5.1 microm; P = 0.021) and significantly smaller than that of the normal biceps femoris muscle (36.1 +/- 6.1 microm; P = 0.028). CONCLUSIONS: The cross-nerve transfer procedure in a dog model was found to prevent muscular atrophy of the external anal sphincter when performed immediately after pudendal nerve transection.     

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.     

Evidence of pudendal neuropathy in patients with perineal descent and chronic straining at stool.

In 17 women with chronic constipation, and abnormal perineal descent on straining at stool, there was more severe neurogenic damage to the external anal sphincter muscle and to its pudendal innervation in those patients with a long history than in those with a short history. These results suggest that recurrent trauma to the pudendal nerves can occur during perineal descent, and that this can lead to denervation and weakness of the external anal sphincter muscle.     

A New Method of Assessing Anal Sphincter Integrity Using Inverted Vectormanometry

Purpose Vectorgraphy as an integrated mapping of radial pressure profiles of the anal canal has been used to attempt identification of pressure-related defects with doubtful reliability since vectorgraphs bear no resemblance to endoanal ultrasound scans at similar levels in the anal canal. This study aimed to devise a technique to enable vectorgraphy to be more representative of sphincter function and integrity. Methods Vectormanometry was performed in 50 patients with anorectal disorders using an Arndorfer pneumohydraulic system. “Normal” three-dimensional manometric images of each 0.5 cm of the anal sphincter were computer-generated by plotting anal pressures at rest and during squeeze radially around a central zero axis. The graphs were replotted with zero at the periphery and maximal anal pressure at the center. Both this (“inverted”) and “normal” vectorgraphs were compared with endoanal ultrasound images at similar levels, assessing both internal and external anal sphincters. Results Standard vectormanometry produced excellent pictures of pressures throughout the anal canal; the anatomy however bore no resemblance to the pictures produced by endoanal ultrasound. The inverted vectographs showed a much better correlation with endoanal ultrasound at each 0.5-mm level of the anal canal, for both squeeze pressure graphs and external sphincter correlations and for resting pressure graphs and internal sphincter correlations. Conclusions Accurate assessment of sphincter integrity is not possible when interpreting the vectormanometry graphs in the current format; however, inverted vectorgraphy gives good correlations with endoanal ultrasound and provides combined functional (pressure measurement) and anatomic (three-dimensional profile) information regarding the anal canal. Presented at the Congress of the International Society of University Colon and Rectal Surgeons, Osaka, Japan, April 14 to 18, 2002.