Should we care about the internal anal sphincter?

The internal anal sphincter is currently regarded as a significant contributor to continence function. Four physiological and morphological aspects of the internal anal sphincter are presented as part of the current evidence base for its preservation in anal surgery. 1) The incidence of continence disturbance following deliberate internal anal sphincterotomy is underestimated, although there is presently no prospective imaging or physiologic data supporting the selective use of sphincter-sparing surgical alternatives. 2) Given that the resting pressure is a measure of internal anal sphincter function, its physiologic representation (the rectoanal inhibitory reflex) shows inherent differences between incontinent and normal cohorts which suggest that internal anal sphincter properties act as a continence defense mechanism. 3) Anatomical differences in distal external anal sphincter overlap at the point of internal anal sphincter termination may preclude internal anal sphincter division in some patients where the distal anal canal will be unsupported following deliberate internal anal sphincterotomy. 4) internal anal sphincter-preservation techniques in fistula surgery may potentially safeguard postoperative function. Prospective, randomized trials using preoperative sphincter imaging and physiologic parameters of the rectoanal inhibitory reflex are required to shape surgical decision making in minor anorectal surgery in an effort to define whether alternatives to internal anal sphincter division lead to better functional outcomes.     

Anorectal sphincter function and rectal barostat study in patients following transanal endoscopic microsurgery

BACKGROUND AND AIMS: This study evaluated the effect of transanal endoscopic microsurgery (TEM) on anorectal sphincter functions and determined the risk factors for anorectal dysfunctions (including incontinence). PATIENTS AND METHODS: A study group of 33 patients with small, mobile rectal tumors (adenoma and carcinoma) located up to 12 cm from the anal verge underwent anorectal motility studies (using pull-through anorectal manometry and rectal barostat) and endoanal ultrasound prior to surgery and 3 weeks and 6 months after TEM; controls were 20 healthy volunteers. RESULTS: Resting and squeeze anal pressures were reduced 3 weeks after TEM. Resting anal pressure remained reduced 6 months after surgery; the changes were related to low preoperative levels and to the internal anal sphincter defects rather than to the procedure duration or the type of surgery. High-pressure zone length and vector volume were decreased 3 weeks after TEM and restored 6 months later. Rectoanal inhibitory reflex, reflex sphincter contraction, rectoanal pressure gradients, threshold and maximal tolerable volume of rectal sensitivity, and compliance were significantly changed 3 weeks after TEM; only rectal wall compliance remained low at 6 months. The rectoanal inhibitory reflex, reflex sphincter contraction, rectal sensitivity, and compliance were related to the extent and type of excision (partial or full thickness). Anal ultrasound revealed internal anal sphincter defects in 29% of patients studied 3 weeks after TEM. Only 76% of patients were fully continent. Disturbed anorectal function (including partial fecal incontinence) was observed in up to 50% of patients at 3 weeks. Partial and moderate anorectal dysfunction was found in 21% patients 6 months after surgery. The main risk factors of anorectal dysfunctions following TEM included: postoperative internal anal sphincter defects, low preoperative resting anal pressure, disturbed rectoanal coordination, extent (>50% of wall circumference) and the depth (full thickness) of tumor excision. CONCLUSION: TEM has a relevant but temporary effect on anorectal motility. As a result of TEM procedures 21% of the patients had disturbed anorectal functions, mostly due to the extent or depth of tumor excision (influencing rectal compliance and rectoanal coordination), and to the sphincter defects lowering resting anal pressure. Preoperative anorectal motility studies and anal ultrasound allow the identification of patients with the risk of postoperative anorectal dysfunctions.     

Patterns of Fecal Incontinence After Anal Surgery

PURPOSE Conservative anal surgery, with maximum preservation of the anal sphincters and continence, is becoming increasingly possible with the emergence of new sphincter-sparing treatments. Many surgeons remain skeptical, however, of the nature and impact of incontinence after anal surgery. We aimed to characterize the patterns of anal sphincter injury in patients with fecal incontinence after anal surgery.METHODS We reviewed our fecal incontinence database and studied a subset developing incontinence after anal surgery. Maximum resting and squeeze pressures and the distal high-pressure zone to mid–anal canal resting pressure gradient were evaluated. Anal ultrasounds were evaluated and specific postoperative lesions were characterized.RESULTS Patterns of sphincter injury in 93 patients with fecal incontinence after manual dilation, internal sphincterotomy, fistulotomy, and hemorrhoidectomy were studied. The internal sphincter was almost universally injured, in a pattern specific to the underlying procedure. One-third of patients had a related surgical external sphincter injury. Two-thirds of women had an unrelated obstetric external sphincter injury. The distal resting pressure was typically reduced, with reversal of the normal resting pressure gradient of the anal canal in 89 percent of patients. Maximum squeeze pressure was normal in 52 percent.CONCLUSION Incontinence after anal surgery is characterized by the virtually universal presence of an internal sphincter injury, which is distal in the high-pressure zone, resulting in a reversal of the normal resting pressure gradient in the anal canal. These data support concerns that non–sphincter-sparing anal surgery leads to fecal incontinence and is increasingly difficult to justify given the availability of modern sphincter-sparing approaches.Presented at the meeting of the Association of Coloproctology of Great Britain and Ireland, July 7 to 10, 2003, Edinburgh, United Kingdom.Recipient of the Colon and Rectal Disease Research Foundation prize for best poster.Reprints are not available.     

Rectal tone and compliance affected in patients with fecal incontinence after fistulotomy

AIM: To investigate the anal sphincter and rectal factors that may be involved in fecal incontinence that develops following fistulotomy(FIAF).METHODS: Eleven patients with FIAF were compared with 11 patients with idiopathic fecal incontinence and with 11 asymptomatic healthy subjects(HS). All of the study participants underwent anorectal manometry and a barostat study(rectal sensitivity, tone, compliance and capacity). The mean time since surgery was 28 ± 26 mo. The postoperative continence score was 14 ± 2.5(95%CI: 12.4-15.5, St Mark's fecal incontinence grading system).RESULTS: Compared with the HS, the FIAF patients showed increased rectal tone(42.63 ± 27.69 vs 103.5 ± 51.13, P = 0.002) and less rectal compliance(4.95 ± 3.43 vs 11.77 ± 6.9, P = 0.009). No significant differences were found between the FIAF patients and the HS with respect to the rectal capacity; thresholds for the non-noxious stimuli of first sensation, gas sensation and urge-to-defecate sensation or the noxious stimulus of pain; anal resting pressure or squeeze pressure; or the frequency or percentage of relaxation of the rectoanal inhibitory reflex. No significant differences were found between the FIAF patients and the patients with idiopathic fecal incontinence.CONCLUSION: In patients with FIAF, normal motor anal sphincter function and rectal sensitivity are preserved, but rectal tone and compliance are impaired. The results suggest that FIAF is not due to alterations in rectal sensitivity and that the rectum is more involved than the anal sphincters in the genesis of FIAF.     

Recovery of anal sphincter function following transabdominal repair of rectal prolapse: Cause of improved continence?

Twenty-eight patients with complete rectal prolapse underwent anorectal manometry before and 6 months and 1–2 years after abdominal rectopexy and sigmoid resection in a study of the mechanisms responsible for postoperatively improved anal continence. Preoperatively, 22 patients reported defective anal control. Seven patients (all with minor incontinence) regained normal control and eight other patients achieved improved continence after surgery. Anal resting, squeeze, and voluntary contraction pressures were significantly lower for defective than for normal control, with a significant rise in these pressures at 6 months after the operation, except for those incontinent patients in whom continence was not improved. No further pressure rise was seen later. Improvement of continence was not accompanied by changes in rectal sensation or reflexive functions of the internal anal sphincter. These results suggest that recovery of the resting and voluntary contraction functions of the sphincter muscles was the cause of continence improvement observed after surgery. Anal manometry was unable to predict outcome of function. Therefore, supplementary procedures for restoration of continence are not advisable, although patients with only minor incontinence are likely to regain full continence after rectopexy alone.     

Rectoanal reflex parameters in incontinence and constipation

PURPOSE: The transient relaxation of the internal anal sphincter in response to rectal distention is believed to play an important role in the continence mechanism. Most anorectal physiology laboratories merely report the rectoanal inhibitory reflex as being either present or absent. This study aimed to assess the parameters of the rectoanal inhibitory reflex in incontinent and constipated patients and healthy control subjects, in an attempt to analyze differences in internal anal sphincter function in these groups. We analyzed each response of the internal anal sphincter to rectal distention with progressively increasing volumes of air at a single site (proximal anal canal). METHODS: Fifty-five constipated and 99 incontinent patients and healthy control subjects underwent manometry. Various parameters of the rectoanal inhibitory reflex were analyzed, and percentage sphincter relaxation was calculated at each volume at which rectoanal inhibitory reflex occurred. RESULTS: There was no difference in the volume of rectal distention required to elicit sensation (P = 0.626) or the rectoanal inhibitory reflex (P = 0.371) in the three groups. There was a significant correlation between the volume required to elicit the rectoanal inhibitory reflex and that at which sensation was first felt only in the incontinent (P = 0.0001) group. Significantly greater sphincter relaxation was seen at each volume (P = 0.001) in the incontinent as compared with the constipated patients. With progressive rectoanal inhibitory reflex, consistently progressive increases in internal anal sphincter relaxation were found only in the incontinent group. This consistent relationship was not seen in the constipated patients or in healthy control subjects. CONCLUSIONS: Assessment of various parameters of the rectoanal inhibitory reflex yielded important information regarding the continence mechanism. Altered responses of the internal anal sphincter in anorectal disorders plays a role in the associated physiologic impairment. This may have significant clinical implications with regard to sphincter-saving resections.     

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.     

Fecal incontinence induced by spontaneous internal anal sphincter relaxation: report of a case

It has been previously suggested that an increase in the frequency of internal anal sphincter relaxations may cause fecal incontinence in patients in whom a structural lesion of the anal sphincter or its nerve supply is not ruled out. We here report a case of fecal incontinence in which the sphincter and its innervation was not damaged, and prolonged recordings of anal resting pressure detected frequent and prolonged internal anal sphincter relaxations. Moreover, a spontaneous improvement in fecal incontinence occurred at the same time as a reduction in the frequency and duration of internal anal sphincter relaxations. This case suggests that prolonged recordings of anal resting pressure are advisable in incontinent patients without detectable lesions of the anal sphincter or its nerve supply to detect any increase in the frequency of internal anal sphincter relaxations as a possible cause of fecal incontinence.     

Pathogenesis of slow transit and pelvic floor dysfunction: from bench to bedside

The colon and anorectum function together to provide intraluminal mixing, absorption of water, electrolytes, and short chain fatty acids, dehydration of fecal material, storage, and ultimately, elimination in a socially appropriate manner. Normal function and continence require accommodation of the colon and rectum to the entry of fecal materials, which includes receptive relaxation, perception, and discrimination of rectal contents, and voluntary and reflex motor function of the anorectum. Defecation, on the other hand, requires the reflex relaxation of the internal anal sphincter, voluntary and reflexive relaxation of the external anal sphincters and pelvic floor structures, and adequate rectosigmoid tone to allow funneling of contents through the anal canal. The sensation of urgency with rectal filling, and the motivation and prior learning of the appropriate responses are also required. Continence and defecation, therefore, involve complex sensory, structural, and motor mechanisms that involve both the colon and pelvic floor. These mechanisms and their relative importance to the pathogenesis of slow-transit constipation and pelvic floor dysfunction will be reviewed.     

The role and technique of ambulatory anal manometry.

Static anal manometry has proved itself a reliable, reproducible and objective assessment of sphincter function in the investigation of disorders of defecation and continence. Despite this, it gives only very limited information on sphincter function due to the unphysiological nature of its measurement. Technical advances, particularly in digital data storage, have made the recording of anal pressure in a normal environment for prolonged periods of time possible. This offers an improved understanding both of anal activity and the interaction of rectal and anal function in normal and pathological states. In normal subjects anal function during a number of normal physiological events such as micturition, passage of flatus and sleep have been investigated. The sampling reflex has been further defined. Abnormalities of the sampling reflex, rectal activity and slow wave activity in the anal sphincter have been demonstrated in a number of pathological conditions of the anorectum and in the states of incontinence or constipation. Effective ambulatory anal manometry remains in its infancy. With continuing advances it offers exciting possibilities in defining normal or abnormal activity of the anorectum and in the investigation of patients with disorders of defecation and continence.     

Physiologic status of the anorectum following sphincter-saving resection for carcinoma of the rectum

The physiologic status of the anorectum after low anterior resections or pull-through operations of the rectum was evaluated clinically and by manometric studies. It was demonstrated that the presence of a normal anal resting pressure and an anorectal reflex were important to achieve postoperative continence after sphincter-saving operations. In patients with anastomotic leaks and poor function, a marked high-pressure zone in the anal canal and an anorectal reflex were not found, but as local inflammation resulting from the anastomotic leak disappeared, these parameters returned to normal. A normal anorectal reflex was found in one of three patients after Bacon-type pull-through operations, but the remaining two showed an increase of anal canal pressure during colonic distention. These results indicate that an elevation of anal-canal pressure in response to colonic distention plays a significant role in fecal continence at the time of “a sense of urgency” if internal sphincter function is impaired. Presented at the 8th Biennial Congress of the International Society of University Colon and Rectal Surgeons, Melbourne, Australia, September 7 to 11, 1980.     

Endosonography of the anal sphincter after ileal pouch-anal anastomosis

PURPOSE: The aim of the present study was to visualize supposed defects of the internal anal sphincter after ileal pouch-anal anastomosis (IPAA) by anal endosonography and to relate these findings with anal manometry and fecal continence. METHODS: We investigated 23 patients, visualized the sphincter complex by anal endosonography, and quantified the anatomic changes of the sphincter. Anal resting and squeezing pressures as well as length of the anal canal were determined by anal manometry. Continence was objectively scored by an observer not involved in treatment of patients and subjectively by patients themselves. RESULTS: At anal endosonography, the mean thickness of the internal anal sphincter was 1.16 mm (95 percent confidence interval, 0.98–1.33), which is significantly less than in normal volunteers. Tapering of the internal anal sphincter only occurred in six patients (of whom two had a gap in the internal sphincter). In 17 patients endosonography showed a thin internal anal sphincter without essential variation in thickness over the complete circumference. Approximately eight weeks after ileostomy closure following IPAA, maximum resting pressure (MRP) and length of the anal canal appeared to be significantly decreased compared with values before IPAA (P=0.001 and 0.002, respectively). These differences were less striking (P=0.05 and 0.04, respectively) when measured six or more months after ileostomy closure,. The extent of reduction of the MRP and thickness of the internal anal sphincter were not correlated with grade of continence or with subjectively scored continence. CONCLUSIONS: IPAA leads to a reduction of thickness of the internal anal sphincter and reduction of the MRP. Tapering or gaps in the internal anal sphincter are probably caused by direct trauma to this sphincter because of mucosectomy, whereas in cases of circular reduction of thickness of the internal anal sphincter without tapering or gaps, direct trauma is an unlikely explanation; this reduction is probably caused by denervation. IPAA compromises continence to a variable degree in 18 of 23 patients. No correlations were found between the extent of reduction of the MRP and the extent of reduction in internal anal sphincter thickness or between these two parameters and objectively or subjectively scored continence. Difficulties in obtaining reliable information on continence may be a causal factor. A striking discrepancy was noticed among objective, scored disturbances in continence, and overall satisfaction concerning level of continence by patients themselves.     

Excision of anal fistula with closure of the internal opening: functional and manometric results

PURPOSE: The aim of this study was to evaluate the results concerning recurrence and continence after sphincter-saving surgery for fistula-in-ano. METHODS: Forty-two patients with anal fistula traversing the sphincter were operated on with fistula excision and closure of the internal opening. Patients answered a questionnaire concerning bowel habits and continence before and 3 and 12 months after surgery. A subgroup of 19 patients were also examined with anal manometry. RESULTS: Twenty-three (55 percent) patients healed primarily after surgery and a further 10 (24 percent) after one reoperation, whereas 7 (17 percent) required 2 to 4 reoperations until healed. In two patients therapy was changed to cutting seton treatment. After 1 year 21 of 36 (58 percent) patients reported improved or unaffected continence and 11 (31 percent) reported a slight and 4 (11 percent) a major decrease in continence. Detailed data on preoperative continence were missing for five patients, and one had a colostomy at late follow-up. Anal manometry showed a significant decrease in resting pressure after three months and a further decrease in both resting and squeeze pressures after one year. CONCLUSION: Surgery for anal fistula with excision and advancement flap has a fairly high initial recurrence rate but a good final success rate. A decrease in continence is seen also after this kind of surgery for anal fistula. Manometric results suggest that this is associated with an impaired internal anal sphincter function.     

Effects of loperamide on anal sphincter function in patients complaining of chronic diarrhea with fecal incontinence and urgency

We have investigated the effect of loperamide (4 mg tds) on the continence to a standard volume of rectally infused saline and anorectal manometry in 26 patients complaing of chronic diarrhea complicated by fecal incontinence and severe urgency. Each patient was treated for one week with loperamide (4 mg tds) and for one week with an identical placebo in a double-blind cross-over trial. Our results showed that as well as its established effects of improving stool consistency and reducing stool weight, frequency and episodes of incontinence and severe urgency, loperamide also significantly improved continence to a standard volume of rectally infused saline. This action was associated with an increase in the maximum basal sphincter pressure, an increase in the rectal volume required to abolish recovery of the rectoanal inhibitory reflex, and a reduction in rectal compliance. These results suggest that loperamide may have a specific action on the anal sphincter, which may aid continence in patients who complain of diarrhea and fecal incontinence.This work was supported by grant no. 252 from the Special Trustees of the Former United Sheffield Hospitals, and by Janssen Pharmaceutica, Beerse, Belgium.     

血吸虫病直肠癌切除术后内部肛门括约肌的疲劳率指数变化

目的探讨血吸虫病直肠癌切除术后内部肛门括约肌的疲劳率指数变化.方法术前,对75例血吸虫病直肠癌术后患者的临床资料进行回顾性评估,其中包括肛门部的静压和挤压的测定,以及疲劳率和疲劳率指数的研究,术后6月,经重复测压及疲劳率和疲劳率指数评估直肠的自制力.疲劳率为每分钟测得的直肠压力变化,疲劳率指数=(挤压-静压,mmHg)/[-(疲劳率,mmHg/min)].结果术前平均静压和挤压为55 mmHg和127.5 mmHg,术后平均静压和挤压为30 mmHg和74.5 mmHg,术前平均疲劳率指数为3.0 min,术后1.3 min,术前术后疲劳率指数有显著差异(P<0.05).结论直肠自制力受内部肛门括约肌的疲劳率指数影响,直肠癌术后疲劳率指数的变化展示其内部肛门括约肌机能的损伤程度,疲劳率指数下降越大,其内部肛门括约肌的损伤越重.     

Injectable Silicone Biomaterial for Fecal Incontinence Caused by Internal Anal Sphincter Dysfunction Is Effective

PURPOSE Fecal incontinence caused by a weak or disrupted internal anal sphincter is common but there has been no effective treatment. This prospective study evaluates the medium-term clinical effects of an injectable silicone biomaterial, PTP^TM (Bioplastique), used to augment the internal anal sphincter.METHOD Eighty-two patients (64 females; median age, 66 years) with severe fecal incontinence and a low anal resting pressure caused by internal anal sphincter dysfunction (defect, n = 11; intact, n = 71) were randomized to PTP^TM injection into intersphincteric space and internal anal sphincter with (Group A, n = 42) or without (Group B, n = 40) guidance by endoanal ultrasound. Both groups were similar in terms of age, gender, past anorectal surgery, duration of follow-up (median, 6 months; range, 1–12 months), and baseline continence score. Sixty-two percent of Group A and 55 percent of Group B had prolonged pudendal nerve terminal motor latency.RESULTS There was no significant complication. Two patients in Group A and four patients in Group B noted minor discomfort at injection sites. At one month postprocedure, endoanal ultrasound confirmed retention of silicone biomaterial without migration. In both groups, fecal continence was significantly improved by PTP^TM implants 1 month after injection, but continued to improve significantly for up to 12 months in Group A and 6 months in Group B (P < 0.001). Improvement in fecal continence and maximum anal resting pressure was significantly greater in Group A, in whom injection was guided by endoanal ultrasound, than in Group B. At three months after injection, significantly more Group A patients than Group B patients achieved >50 percent improvement in Wexners continence score (69 percent vs. 40 percent; P = 0.014). Ninety-three percent of Group A and 92 percent of Group B had >50 percent improvement in global quality of life scores (visual analog scale). At a median follow-up of 6 months, all domains of the fecal incontinence quality of life scale improved significantly in both groups; however, the physical function and mental health scores of Short Form-12 only improved in Group A. A prolonged pudendal nerve terminal motor latency had no effect on functional outcome in either group.CONCLUSION Injection of silicone biomaterial provided a marked improvement in fecal continence and quality of life in patients with internal sphincter dysfunction, despite the presence of pudendal neuropathy.Read at the meeting of The American Society of Colon and Rectal Surgeons, Dallas, Texas, May 8 to 13, 2004.     

Impact of two different types of anal retractor on fecal continence after fistula repair

Purpose This study was designed to compare two different types of anal retractors (Parks vs. Scott) with regard to their impact on fecal continence after fistula repair. METHODS: Between November 2000 and November 2001, 30 patients were randomized into two groups. In Group A (n = 15), a Parks retractor was used during fistula repair, whereas in Group B (n = 15), the repair was performed with a Scott retractor. Before and three months after surgery, maximum anal resting pressure and maximum anal squeeze pressure were recorded. In addition, continence status was evaluated using both the Rockwood Fecal Incontinence Severity Index and the scoring system according to Parks. RESULTS: In Group A, the median anal resting pressure dropped from 76 mmHg to 42 mmHg. In Group B, no significant difference was observed between the preoperative and postoperative anal resting pressure. The difference in the changes from baseline between the two groups was statistically significant (P = 0.035). No significant changes in anal squeeze pressure were observed. In Group A, the median Rockwood fecal incontinence score increased from 0 to 12. In Group B, the median Rockwood fecal incontinence score did not change after the operation. The difference between the two groups was statistically significant (P = 0.038). CONCLUSIONS: The use of a Parks retractor during perianal fistula repair has a deteriorating effect on fecal continence, probably because of damage to the internal anal sphincter. Because this side effect was not observed after the use of a Scott retractor, we advocate the use of this retractor during all fistula repairs. Read at the meeting of the Netherlands Association of Surgery (NWH), Scheveningen, the Netherlands, May 30 to 31, 2002.     

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.     

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.     

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

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