Intestinal motility after ileal pouch-- anal anastomosis

Colectomy, mucosa! proctectomy and ilea! pouch-anal anastomosis, has become the procedure of choice for carefully selected patients with ulcerative colitis requiring surgery. Pathophysiological studies after the operation have led to a better understand mg of the mechanisms of continence and to the development of new technology to study anorectal function. Manometric studies of the anal sphincter, ilea! pouch and distal ileum have shown that the operation alters the mechanisms of continence. The maximal tolerable volume of distension of an ilea! pouch often approximates that of a normal rectum and yet the functional outcome may differ from a well functioning ileorectal anastomosis. Many other factors influence the result of the operation. The influence of the pattern of motility of the proximal and distal small bowel has been evaluated. The ileal pouch accommodation to distension has been correlated to clinical outcome. Scincigraphic techniques were designed to study the relationship betwet>n motility, fi lling and emptying of the ilea! reservoirs. Measures designed to slow intestinal transit, increase absorption and reduce stool output are under investigation. Can J Gastroenterol 1990;4(7):432-435

La motilite intestinale apres anastomose ileo-anale avec reservoir ileal RESUME: La colectomie avec mucosectomie rectale et anastomose ileo-anale avec reservoir ilea! est une intervention de choix pour les patients atteints de colite ulcereuse qui doivent etre open~s.Les etudes physiopathologiques apres cette intervention ont permis de mieux comprendre les mecanismes de la continence et de developper de nouvelles technologies pour en etudier la fonction.L'etude manometrique des sphincters de l'anus, du reservoir Mal et de l'ileon distal a demoncre que !es mecanismes de continence sont modifies apres !'operation.Bien que la capacite du reservoir mesuree selon le volume maximal tolerable de distension est parfois bien similaire a celui d'un rectum normal, le resultat peut etre different d'une anastomose ileo-rectale.L'influence de la showed that commence requires two distinct mechanisms.Reservoir continence depends on plastic a<laptauon of the smooth musc le of the colon and rectum.When this adaptation reaches its limit, sphincleric continence comes into play.Formal labora tory investigations of ilea! reservoirs constructed to replace the rec tum we re reported by Valiente and Bacon ( 5) in 1955.Karlan and colleagues (6) in 1959 noted rhat J ogs with a n ilea! reservoir fashioned proximal to an ileoanal anastomos~ had a greate r Jegree of continence than J ogs without a reservoir.In 1969, Kock (7) described an internal reservoir and later showed that its presence was consistent with normal intestinal function (8).
The fa vora ble cl mical report and technical considerations of Martin m l (9,10) in pe rforming total colectomy and Soave e ndorectal anastomosis for ulcerative colitis revived interest in the ileoanal anastomosis.The clinical outcome after straight ileoanal anastomosis in aJults was not as good as in the pediatric group: the overall adult failure rate was 33% ( l l ).
In 1978, an operation in which an ilea! reservoir was constructed proximal to an ileoanal anastomosis was JescribeJ in humans (9).Since then, various types of ilea! reservoirs have been Jescri heJ ( I 0, 11 ) .
Many invemgacors have studied the mechanisms hy which continence can be maintained in patients following these operations.The purpose of this article is to review some aspects of 111testinal monlity after ilea! pouch-anal anastomosis and their relation tn clinical outcome.

MECHANISMS OF FECAL CONTINENCE IN HEALTH
The main functions of the rectum and anus are to preserve fecal contmence so that one can defer defocanon voluntarily, Jistingu1sh solids, liquids and gases, and maintain nocturnal control.The physiology of continence 1s complex and the mechanisms involve both conscious and unconscious components.An understanding of the normal physiology of continence provides a background against which the effect of total colectomy, mucosa!pmcteccomy and deoam1l anastomosis must be compared ( 15).
To achieve continence, several physiologic mechanisms interact: the resistance of the anal sphmcters, anorectal angulatmn, rectosphinctenc reflexes, the reservoir function of the distal bowel, sensory mechanisms, the volume and consistency of stools and the effect of intestinal propulsion.Anal continence results from a balance between the consistency and rate of delivery of rectal contents and the competence of the anorectal structures together with suppression of the urge to defecme.months) and the likely permanent im pairment of resnng tone.However, no correlation between resting pressure anJ con11nence was found in thar study.A low resting pressure was associated with a high frequency of bowel movements and poor deferral (less than 30 mins).

ALTERED PHYSIOLOGY
To facilitate the mucosectomy and to reduce the risk of remaining rectal mucosa, the rectal wall is often divided close to the levators (23).The 111tramural neural pathways mediating the rectoanal 111h1h1tory reflex arc d1v1ded.Continence after ileoanal anastomosis is not significantly impaired by the absence of this reflex ( 17,24,25).The ability to dist111gu1sh stool from flatus seems to he mdependent of this reflex.
Moreover, Grant et al (25) have shown that the clinical results and manometric findings after restorative proctocolectomy are similar with long and short rectal cuffs.Whether or not the mucosa!sensory zone proximal to the dentate line shoulJ be preserved to enhance sensory discrimmation of enteric content remams controversial.The neorectal angle: The puhorectalis muscle normally pulls the anorectal junction toward the pubis, thus creating a 'flap valve' mechanism which contributes to continence in s1tuat1ons CAN J GMffROENTEROL VOL 4 No 7 NOVEMAl:R 1990 Motility after IPPA where a su<lden mcreasc 111 mtra-abdominal pressure exceeds the mtra luminal anal canal pressure (cg, the Valsalva maneuvre).It was postulated that since .dil)f the J1sscct1on 1s per-formeJ intrarecrnlly, the pubnrecral1s ling of the levarnr ant complex would remain intact.A completely open annneorectal angle may be related to postnrerati ve leakage.In topographic assessments of ileoanal reservoirs, LmJqu1st ct al (26) were not able to confirm this assumption.Using lateral neorectal scintigraphic scanning, O'Connell ct al (27) have shown that the anal-pouch angle after the operaunn differs little from the annreual angle in health.

ILEAL RESERVOIR
The rationale for us111g an ilea! reservoir 1s to attempt to provide an adequate replacement for the rectum hy cnnstruccmg a low pressure, compliant, less propulsive reservoir which can evacuate spontaneously at a reasonable threshold volume.Using a soft latex balloon to distend the distal nowel the present author found that the mean tolerable volume of neorecrnl distension 11 months after ileoscomy '-losure in a group of 12 patients with straight ilcoanal anastomosis was 248±31 mL versus 406±26 mL in l 0 healthy controls ( 16).He also observed that the greater the maximal colerahle volume of ncorectal distension, the smaller the number of bowel movements per day (r=0.9;P<0.001).From c.linical obscrvanons, Taylor et al (28) have noteJ that the greatest benefit of the reservoir may be in the early months after sromal closure, at which time stool frequency was significantly reduced.lleal capacuy and compliance increase progressively during the postoperative period (19,29).Indeed, the maximum capacity and distens1bility of the ileal 'J' pouch have been found to approxunatc that of a normal rectum ( 17,30).
The motility of the terminal ileum after straight ileoanal anastomosis was evaluated by inserting a perfuseJ catheter above the anal sphincters cransanally after an overnight fast.Two types of pressure waves were found m the ileum: small amplitude wave~ ( 14 cmHzO) of short duration and large amplitude waves (mean 66 cmH20) of longer duration (31 ).These large waves corresponded to che classic 'type IV waves' initially described by Code et al (32) in 1957.Clearly, the urge to defe-caLe occurred concomitant with these large pressure waves and leakage occurred as the peak amplitude of these waves exceeded the resistance of the anal sphincter~.The paltem of ileal motility contributed to clinical results in these patients.ConsLruction of an ileal reservoir increase<l the volume ac-commo<lated within the terminal ileum and reduced the mean amplitude of the ilea[ pressure waves (24).In the nonnal rectum only infrequent and low amp I itude contractions are detected, even with distension to maximum capacity (16).Luminal distension has been shown to stimulate large pressure waves in the ileum.Rabau et al (33) found that a distending volume of only 30 mL was necessary to trigger these contractions in the ileum proximal to a Brooke ileostomy, whereas 322 mL was required to induce these contractions in the ::,' pouch.The frequency and amplitude of the large pressure waves increase with time during fasting as the ilea!pouch fills ( 17,31 ).These waves are abolished by evacuation of stool.
Stryker er al ( 17) have shown that the mterval of onset of the large pressure waves after evacuation was significantly related to stool frequency.O'Connell et al (30) demonstrated that the volume of ileal distension at which the large pressure waves appear ('threshold volume') is an important determinant of stool frequency.The threshold volume is a function of both the capacity and the compliance of the ilea!reservoir.In patients with active colitis, Rao et al (34) have shown that the distal bowel reacts to intraluminal contents by generating vigorous contractions that challenge the continence mechanism, an<l cause frequent, urgent and painful defecation.
In an experimental assessment of pelvic ileal reservoir function compared to that of a normal rectum, Cran-Icy et al (35) found that while satisfactory continence could be 434 achieved by an tleal reservoir, the ability of normal rectum to evacuate completely was disturbed.Similarly, using a semisolid rad1onucli<le enema to assess ilea! pouch emptying quantitatively, the author found that the ilea!pouch emptied less efficiently than a normal rectum (36).ln contrasL, others have found that the ileal 'J' pouch empties as well as Lhe healthy recrum (17,37); hut no overall differences were found between the efficiency of pouch evacuation and frequency of stools (36,37).Moreover, pouchitis may not always he related co poor emptying (36)(37)(38).
Quigley et al (39) observed large amplitude pressure waves in the distal 20 to 30 cm of healthy ileum.After the operation, these waves were also detected up to 125 cm proximal to the ileal pouch hy Stryker ct al (40).The migrating motor complexes found in the jejunoileum <luring fasting remain unchanged as shown by Stryker ct al (40) and Chaussade et al (41).These investigators also observed the presence of discrete clustere<l contractions in the proximal small bowel previously described in partial small intestinal obstruction by Summers et al (43 ).The relationship between jejunoileal motility and function of Lhe ileal reservoir remains unclear.The rate of delivery of stools into the neorectum may facilitate accommodation to distension.

STOOL OUTPUT
After straight ileoanal anastomosis, the author found a mean total daily stool volume of 598±60 g, similar to that after Brooke ileostomy or after a well functioning Kock pouch (16).When the normal absorptive function of the colon is present, a mean volume of 1 SO g is expected.This increase in stool volume may explain the increased frequency of evacuation after operation.After ilea! pouch-anal anastomosis, O'Connell et al (30) found that the volume of stool passed per day is the most important determinant of stool frequency.In patients with ilcostomy the output depends on the amount of fibre in the diet.Loperamide was reported by Emblem et al ( 43) rn reduce fecal output significantly after ileoanal anastomosis, probably by mcreasing transn time, which promoted absorption of water and electrolytes.Recently, Soper et al ( 44) showed that infusion of oleic acid into the deal pouch slowed gastric emptying and small bowel transit and delayed defecation.An 'ilea!brake' on gastrointestinal transit is functional after ilea! pouch-anal anastomosis.
In conclusion, measures that slow intestmal transit, increase absorption and reduce stool output woulJ be clinically beneficial.Moreover, new technology will aid understanding o( the pachophysiology of adaptation following these operations and improvr resu I ts ( 4 5).Tb is review of several aspecLs of intestinal motility after ileal pouch-anal anastomosis Jemonstrntes how continence can be restored surgically nHscd on an expanding knowledge of applied gastromrcstinal physiology gained in the l::iborntory by dedicated investigators (46).