Surgical Management of Constipation

13Surgical Management of Constipation

Ian G. Finlay and Andrew A. Renwick

1. Introduction

Many patients complain of constipation but few require surgery. Whilesymptoms may be improved when surgery is performed, injudicious inter-vention may make symptoms worse, causing patient discontentment and,all too frequently, litigation. Consequently, a carefully planned strategy isrequired for the identification of those patients who will benefit fromsurgery and for the selection of an appropriate operation. In this chapterthe authors describe the protocol used in the Department of Coloproctol-ogy, Glasgow Royal Infirmary, for the investigation and management ofpatients with severe constipation referred for a surgical opinion.

Constipation is a generic term that may imply a number of differentsymptoms [1] and at the outset the clinician requires to elicit which of thesesymptoms is predominant. In the first instance, it is important to determinethe duration of symptoms. Are they life-long, dating to childhood (as in idiopathic slow-transit constipation, Hirchsprung’s disease, or megarectum)or do they have a clear precipitating factor (postchildbirth, postpelvicsurgery, or after severe gastroenteritis)? What does the patient mean byconstipation? Is it the complete absence of the call to stool with bloatingand nausea (as in slow transit) or is it a sensation of weight and fullness inthe perineum with a sensation of incomplete evacuation (as in perinealdescent syndrome and rectal intussusception/prolapse)? Does the patientdigitally aid defaecation by supporting the posterior vaginal wall, the classicsymptom of rectocoele, or do they attempt to provide support behind theanus, a feature of generalised weakness of the pelvic floor with perinealdescent? Finally, it is important to identify whether the most troublesomesymptom is pain. Patients who benefit most from surgery for constipationdo not report pain as a prominent symptom.The presence of severe abdom-inal pain should raise the suspicion of underlying irritable bowel syndrome,an absolute contraindication to surgical intervention.

When patients are referred for a surgical opinion for constipation theyhave usually already had a full range of laxatives and basic investigations.

262

It is important, however, to be aware of any medications that may con-stipate such as analgesics, psychotropics, or the use/over use of over-the-counter medicines. All patients should have thyroid function tests anda radiological examination of the large bowel. Every year we identify 2 or3 patients with previously undiagnosed myxoedema in whom symptomsresolve when thyroxine is prescribed. It should also be noted that myx-oedema is associated with rectal prolapse/intussusception. A contrast studyis preferred to colonoscopy because in addition to excluding a carcinoma,contrast study gives an indication of the diameter of the hindgut and allowsa major distinction to be made between patients. Individuals can be classi-fied as having constipation with a normal caliber colon/rectum or consti-pation with a megabowel.

A contrast study also gives an impression of the redundancy of the boweland may identify the presence of colonic volvulus.

2. Severe Constipation and Normal Caliber Colon/Rectum

2.1. InvestigationsHaving identified that the patient has a normal diameter colon and rectum,the two most useful and easily performed investigations are evacuationproctography and a colonic transit study [2]. The colonic transit study cru-cially confirms that the patient has objective evidence of severe constipa-tion. The test does not need to be complicated and can be performed in anyhospital with X-ray facilities. Patients are given 20 inert markers (SimsPortex®) to swallow and advised to avoid using laxatives or enemata. Thepresence of 5 markers at 5 days after ingestion on a straight abdominal X-ray indicates constipation, more than 5 markers indicates severe constipa-tion. This is an important initial test because many patients referred withconstipation, who consider their symptoms to be severe, will have a normaltransit study. Although more complicated scintigraphic and differentialtransit studies have been described and can be useful, it is not the authors’practice to use these at this screening stage. The value and role of proctog-raphy is more controversial and less well defined because it is less objec-tive. It will, however, identify gross anatomical abnormalities and thosepatients with obstructed defaecation or anismus who are unable to emptyeven liquid from the rectum due to pelvic-floor spasm. On the basis of theseinvestigations there are 4 possible combinations of results (Figure 13.1) thatare used to determine the need for further investigations and the devel-opment of a treatment plan. These are: (a) delayed transit and a normalproctogram, (b) normal transit and an abnormal proctogram, (c) delayedtransit and an abnormal proctogram, and (d) normal transit and a normalproctogram.

13. Surgical Management of Constipation 263

264 I.G. Finlay and A.A. Renwick

2.1.1. Delayed Colonic Transit and a Normal Proctogram (Slow-transit Constipation)

The combination of delayed colonic transit and a normal proctogram typically identifies those patients who have slow-transit constipation, thatis, patients who have objective evidence of delayed transit and normal evac-uation. The symptoms may be either idiopathic or attributed to a specificevent such as childbirth, hysterectomy, or, occasionally, severe gastroen-teritis. These 2 distinct clinical patterns probably have a different patho-physiology although they are frequently reported together as a single entity.Classical idiopathic slow-transit constipation (ISTC) is a disorder of youngfemales, in whom the symptoms are life-long, dating to childhood. Patientswith ISTC have an absence of the call to stool with symptoms of nauseaand abdominal distension. Bowel movements may be as infrequent as onceevery 2–3 weeks and then only with the use of laxatives. Although thesepatients may complain of abdominal discomfort (especially prior to evacu-ation), pain is not a prominent symptom and if present should raise the suspicion that the underlying diagnosis is one of irritable bowel syndrome.Surgery should be avoided in patients in whom pain is the predominantsymptom because it is rarely successful [3].

The exact aetiology of idiopathic slow-transit constipation is unknownbut it may have a genetic basis because there is frequently a positive familyhistory [4]. Several studies have shown an abnormality of colonic motilitycharacterised by a reduction in the frequency, amplitude, and duration of

NORMAL CALIBRE BOWEL

Barium Enema & Thyroid function tests

Megabowel(see Part B)

Colonic Transit Study & Proctogram

Delayed Transit

Normal Proctogram

Idiopathic slow transit constipation

Colectomy and Ileorectal anastomosis

Precipitating factor (childbirth/hysterectomy)

Delayed Transit

Abnormal Proctogram

Uncertain

Biofeedback +/- Colostomy

None

Normal Transit

Abnormal Proctogram

Intussusception/prolapseRectocele

Resection rectopexy

Repair of rectocele

Anismus(Biofeedback)

Normal Transit

Normal Proctogram

Functional bowel disorder

None

None

Diagnosis

Surgery

Exception

Figure 13.1. Flow chart demonstrating the investigative pathway in constipatedpatients.


propulsive contractions in the large bowel [5]. There is a similar abnormal-ity in the small bowel where spontaneous mechanical activity arises fromelectrical activity of lower intensity and of shorter duration [6] than in con-trols. It has been suggested that these features may be related to a colonicsmooth-muscle myopathy that in turn leads to the inability of the surfacemembrane to initiate and maintain periods of high-frequency spike activity [5,7].

At the biochemical level, abnormalities have been identified in both nitricoxide synthetase and vasoactive intestinal peptide-containing neurons [8,9],which may explain the observation that there is a myenteric nerve abnor-mality with a functional cholinergic deficit in response to electrical stimu-lation [10,11]. Quantitative tests suggest the presence of a small-fibreneuropathy [4]. In addition, it has recently been reported that the intersti-tial cells of Cajal that are required for normal intestinal motility are reducedthroughout the colon and rectum [12,13], suggesting that this is an ab-normality of the entire lower gastrointestinal tract. It may also extend tothe upper gastrointestinal tract because it has been shown that patients whofulfil the clinical criteria given above for ISTC have evidence of delayedgastric [14,15] and gallbladder [16] (Figure 13.2) emptying with prolonged

Figure 13.2. Cholecystokinin provacation testdemonstrating delayed gallbladder emptying.

small-bowel transit [17,18]. It is unknown, however, whether this a mani-festation of a pan-gastrointestinal disorder or whether upper gastrointesti-nal delay is secondary to colonic inertia because it has been shown thatinflation of a balloon in the rectum of humans and animals inhibits theentire gastrointestinal tract [19,20]. In an attempt to answer this question,gastric emptying has been measured before and at 1 year after total colec-tomy and ileorectal anastomosis for ISTC [21]. Although gastric emptyingimproved in the majority of patients, it returned to normal in only one halfof those studied, suggesting that the extent of the abnormality is variable[10]. Unfortunately, the severity of the gastric-emptying abnormality priorto surgery did not predict the functional outcome afterwards.

It should be noted that idiopathic slow-transit constipation as describedabove is an uncommon condition occurring in <5% of patients referred toGlasgow Royal Infirmary for consideration of surgery for constipation. Inreports from the Cleveland Clinic and Sweden the corresponding figuresfor patients fulfilling the criteria of delayed colonic markers and normalevacuation as assessed by cinedefaecography or electromyography [22]were 13% and 7%, respectively.The authors have not found anorectal man-ometry, electrophysiology, or balloon evacuation studies helpful in thisgroup of patients when making a decision as to whether these patientsshould have surgery.

2.1.1.1. Surgery

The most effective operation for idiopathic slow-transit constipation iscolectomy and ileo–rectal or ileo–sigmoid anastomosis. The outcome aftersurgery, however, is unpredictable with reported success rates varying from30%–100%, reflecting the clinical and physiological heterogeneity of thepatients included in these reports. Despite this, some firm conclusions canbe made. Fewer than 50% of patients who have a colectomy performed onthe basis of clinical criteria alone, without the use of investigations, have asatisfactory outcome [3,23]. Further, failure after surgery often results in anileostomy. Consequently, patients should never be subjected to surgerywithout investigation. In contrast, there have been several reports of theoutcome after surgery based upon the selection criteria of a delay in colonicmarkers and a normal proctogram. These show consistently high successrates for the operation of over 90% [22,24–26]. Patients must be clearly con-sented prior to surgery that there is a risk of either continuing constipationor intractable diarrhoea that may in turn lead to the need for a permanentstoma. When performing the colectomy in these patients it is the authors’practice to leave a short segment of sigmoid colon, preferring to risk adegree of residual constipation rather than incapacitating diarrhoea.

In an attempt to overcome the risk of intractable diarrhoea, segmentalcolonic resection has been advocated [27,28] and when it is based on scintigraphic transit studies then the outcome may be comparable to total



colectomy [29]. Crucially, scintigraphic transit studies have suggested thatthere may be different patterns of segmental slow-transit constipation withthe abnormality restricted to either the right colon or the distal large bowel[30] (Figure 13.3). This later abnormality has been especially identified inthose patients who clearly attribute the onset of symptoms to childbirth orhysterectomy. Patients complaining of posthysterectomy constipation havebeen shown to have abnormal colonic motility with mass inaction extend-ing from the splenic flexure to the rectum [31], leading to the suggestionthat this abnormality is related to an iatrogenic autonomic-nerve injuryduring pelvic dissection. A similar abnormality has been shown in patientswith postchildbirth constipation [14,32,33] both on colonic manometry and bisacodyl-stimulated intraluminal scintigraphy [34]. The difference inthe pathophysiology between idiopathic slow-transit and postchildbirth/hysterectomy constipation is further emphasized by the observation thatgastric emptying is normal in postchildbirth/hysterectomy constipation andabnormal in patients with idiopathic constipation [35]. This raises the pos-sibility that hindgut resection could remove their constipation by removingall colon from splenic flexure to the anal canal. The disadvantage to such amanagement plan were it to fail is that the patient has lost the option ofhaving an ileal pouch.

In 1990, Malone introduced the alternative surgical approach of ante-grade colonic irrigation using an appendicostomy [36]. The Malone ante-grade continent enema (MACE) has since proved to be safe and effectivein children suffering from constipation secondary to spina bifida or ano–rectal malformations [37]. More recently, it has been used to treat a smallnumber of adult patients with neurogenic colorectal dysfunction andchronic idiopathic constipation [38,39]. Further, using a novel scintigraphic

Figure 13.3. Radiolabeled scintigraphy scan demonstrating delay at splenic flexureafter 24 hours. In normal subjects this would be in the rectum.

technique it has been shown to be effective [40] in clearing the bowel. Thistechnique may have an increasingly important role in the future.

2.1.2. Normal Colonic Transit Study and an Abnormal Proctogram

Videoproctography is the best readily available investigation for identify-ing abnormalities of evacuation [41]. Newer techniques include dynamicmagnetic resonance proctography [42], dynamic anal endosonography [43],and scintigraphic proctography but these have either been studied in onlysmall numbers of patients or remain research tools. Approximately 20%–30% of patients presenting to a specialist clinic with constipation will havethe combination of an abnormal proctogram and a normal colonic transitstudy. Consequently, this is a relatively common clinical problem thatrequires a clear management strategy. Proctographic abnormalities may bebroadly defined as anatomical or functional. The former include evidenceof rectocoele, internal prolapse, perineal descent, and atypical herniationsincluding enterocoele and levator ani defects [44]. The principle functionaldefect is that of anismus or puborectalis paradox.

Anatomical abnormalities of the anorectum are predominantly, althoughnot exclusively, found in female patients in middle and later life. Symptomsinclude difficulty in evacuation, a sensation of incomplete evacuation, or asensation of weight in the perineum that initially may be described as pain.Patients may digitally aid defaecation by supporting the posterior wall ofthe vaginal or by pushing against the buttock behind the anus. Some may digitally evacuate the bowel. Patients also often respond positively to thesuggestion that the energy they produce in pushing to achieve evacuationis strangely lost, resulting in a feeling of exhaustion. On occasions patientsmay be aware of prolapse of either the bowel or the vagina. Frequentlypatients have already had urological and gynaecological operations includ-ing hysterectomy or vaginal-wall and bladder-neck repairs. It is wise toinvolve these specialists [45] at an early stage and several centres now havejoint pelvic-floor clinics involving all 3 disciplines. It is of note that in somecountries there is emerging the entity of the pelvic-floor specialist.

In broad terms, these anatomical abnormalities are due to wear and tearand are predominantly secondary to childbirth. It has been shown that evenan apparently normal vaginal delivery results in neuropathy of the puden-dal nerve with reduced tone in both the external anal sphincter and pub-orectalis muscles [46,47]. Multiple pregnancies and complicated deliveriesinvolving the use of forceps or other interventions produce an even greaterdegree of injury.The levator ani muscle may be similarly damaged by eithera traction or ischaemic injury to the nerves arising from S2,S3 which courseover the ventral surface of the posterior aspect of the muscle, although it should be noted that the exact nerve supply to the levator muscle remains uncertain. It is widely accepted that this is the mechanism that leadsto the development of the appearances of perineal descent syndrome



(Figure 13.4) and eventually those of idiopathic faecal incontinence. Manyof these features are also present in patients with rectal prolapse althoughthe sequence of events that leads to the development of a prolapse is uncer-tain. Neuropathy can certainly rapidly lead to a rectal prolapse as evidencedby reports of a rectal prolapse developing within days of spinal surgery thatinvolved transection of the cord. With regard to the present discussion, it isunknown whether a rectal prolapse always begins as an intussusception and

Figure 13.4. Combined proctogram and cystogram that demonstrates perinealdescent, rectocele, and posterior rotation of the urinary bladder.

if it does, then over what time scale. This has important implications withregard to the selection of patients for surgery who have intussusception on proctography. The management of the common abnormalities found onproctography are discussed below.

2.1.2.1. Intussusception/Internal Prolapse

Patients with symptoms of obstructed defaecation frequently have evidenceof infolding of the rectum on videoproctography [48,49] (Figure 13.5). Thisappearance is known as internal prolapse or midrectal intussusception.Over quarter of a century ago it was recognised that some patients with this feature respond to surgery while others are either unhelped or madeworse [50]. For example, in 1975, Ihre and Seligson observed that patientswith symptoms of prolapse and incontinence had a good result after rec-topexy but the outcome was poor if patients complained of obstructedsymptoms or had a solitary rectal ulcer. Several surgical groups have sincereported similar results leading to a reappraisal of the indications forsurgery in this condition [51–53]. Indeed, in a recent comparative study ithas been suggested that biofeedback should be used as the initial treatmentfor most patients with a rectal intussusception [54]. The reason for thischange in opinion with regard to management is directly related to a betterunderstanding of the range of normal appearances on videoproctograms.When infolding of the rectum was initially identified it was assumed to bethe principal cause of symptoms in patients with obstructed defaecation. Itis now recognized that a small degree of rectal infolding may be present innormal subjects. Further, when it occurs in patients with symptoms ofobstructed defaecation it is probably secondary to recurrent strainingrather than the primary abnormality. The situation is further complicatedby the fact that the infolding may involve only mucosa or include the fullthickness of the bowel wall. In either case, the size of the intussusceptionmay vary from <1 cm to a prolapse protruding at the anus. It is also nowrecognised that very small intussusceptions rarely proceed to overt pro-lapses, at least over a 10-year observation period [54]. Despite this, an overtrectal prolapse must have a stage when it is a midrectal prolapse/intussus-ception which does not reach the anal verge. The clinical picture is furthercomplicated by the fact that even overt prolapses may be evident only whenthe patient strains and can be difficult to diagnose. In conclusion, there areprobably 2 distinct entities: mucosal infolding and small full-thickness intus-susceptions that are secondary to obssesive straining, and large intussus-ceptions, which are early prolapses secondary to a pelvic-floor neuropathy.

In order to distinguish these 2 entities, the authors use the following strategy: all patients in whom the proctogram suggests an intussuscep-tion proceed to examination under anaesthesia (EUA). An eissenhammerretractor is inserted into the anal canal and the midrectum is drawn down-wards using a sponge-holding forcep. When the full thickness of rectum iseasily drawn to the anal margin without tension, the patient is considered



to have a true intussusception/prolapse. If the patients symptoms correlatewith this finding (i.e., sensation of weight, feeling of prolapse) then they areoffered a resection rectopexy. Examination under anaesthesia is also performed in those patients who have classical symptoms of prolapse butin whom an intussusception has not been identified on proctography. This

Figure 13.5. Defaecating proctogram identifying a midrectal intusussecption.


excludes or confirms the presence of a midrectal intussusception. Patientsselected in this way have a similar outcome to those who have rectopexyfor overt rectal prolapse, further confirming that the 2 conditions are inter-related [55]. Those patients who have lesser degrees of intussusception oronly mucosal prolapse are treated by biofeedback.This later group includesmost patients with solitary a rectal ulcer unless there is evidence of a grossprolapse at EUA.

2.1.2.3. Rectocoele

Rectocoele arises from laxity of the rectovaginal septum. It should be notedthat all female patients have a small physiological rectocoele on proctog-raphy. Consequently, the rectocoele should have a diameter of at least 5 cmbefore it is considered to be of clinical significance. In determining whetherto offer a patient an operation for rectocoele, the single most important pre-dictive factor is to obtain from the history that the patient is able to achieveevacuation by digitally supporting the posterior vaginal wall. This symptomhas been shown to correlates with both the size of the defect on X-ray [56]and outcome after surgery. Proctography alone, however, has no prognos-tic significance regarding the outcome of surgery [57] (Figure 13.6).

Figure 13.6. Defaecating protogram demonstrating a large rectocele.

Rectoceles may be repaired by the transanal, transperineal [58], or trans-vaginal routes. They can also be repaired using both a transanal and trans-vaginal approach [64] or by the using circular stapling devices [60]. Thereare advocates for each technique. The authors favor a modified transanalrepair first described in 1968 by Sullivan et al. [61]. The patient is placed inthe prone position and using an anal speculum a transverse incision is madein the rectal mucosa.The rectal-wall muscle is then plicated obliterating therectocele.Although there are few reports of functional assessment after thistype of surgery, the operation is considered to be successful in over 80% ofcases [62,58]. Ho et al., however, have suggested repair be avoided in thosewith weak anal sphincters [63]. There are relatively few complications butcare must be taken to avoid damage to the vagina, which may lead to a rec-tovaginal fistula. Similar results have been reported using other techniquesincluding mesh repairs by the perineal route. Prospective randomised trialsare notably lacking. Irrespective of the technique used, infrequent stool frequency has been shown to lead a poor outcome [59]. There is variableevidence regarding outcome if the patient also has anismus but this shouldnot be considered a contraindication to surgery [64].

Rectocoele has been observed in men who have had radical prostatec-tomy [65], but is unknown whether transanal repair helps these patients.

2.1.2.4. Anismus

Anismus is a functional abnormality of the anorectum in which anal-canalpressure rises during attempted evacuation with closure of the sphinctermechanism and failure of evacuation. The condition is variously referred toas obstructed defaecation or pubrectalis paradox. It may be difficult to becertain of the diagnosis because voluntary contraction of the pelvic floorwith closure of the anorectum is the normal response to avert the call tostool. It is not surprising for normal subjects to show evidence of puborec-talis contraction during straining in the artificial and embarrassing envi-ronment of the anorectal physiology laboratory. As a result, anorectalmanometry, electromyography, and balloon expulsion tests are of minimaldiagnostic value due to the high false-positive rate, but these tests may beuseful in monitoring treatment after the diagnosis has been made.The mostreliable method for diagnosing anismus is proctography [66]. Although adelay in evacuation of 30 seconds is considered to be important [18], in theauthors’ experience proctography also has a high risk of producing false-positive results, especially in anxious patients who will voluntarily contractthe pelvic floor and sphincter due to embarrassment. Fortunately, in thesepatients the true diagnosis can be easily confirmed. Those patients with vol-untary anismus will empty without difficulty if given the opportunity to doso in privacy. In comparison, patients with anismus will not empty contrastmaterial for at least 24 hours and in severe cases for several days (Figure13.7).



The aetiology of anismus is unknown but it is usually attributed to inap-propriate contraction of the puborectalis muscle despite the fact that thereis relatively little evidence to support this as the primary abnormality [67].Further, the mechanism whereby this could occur is unknown although ithas been suggested that it may result from a failure of coordination betweenthe hindgut and the anorectum [68,69]. Alternatively, it may simply be alearned event as a component of an obsessive neurotic behavioral disorder.Evidence to support a psychological aetiology may be found in the obser-vation that anismus diagnosed by manometry was found in 97% of indi-viduals who had been subjected to sexual abuse and in only 30% of controlssubjects [70].

Surgical treatments for anismus (e.g., puborectalis muscle division) havebeen abandoned because they are ineffective and have a of risk inconti-

Figure 13.7. Defaecating proctogram that demonstrates anismus or obstructed defaecation.


nence. For the past decade it has been widely accepted that biofeedback isthe treatment of choice for anismus [71,72] although the mode of action isuncertain. It has been suggested that biofeedback may actually modifyhigher centre control of defaecation [73]. Several studies have shown thatthe patients who gain most benefit are those who have no abnormality ofthe anorectum on physiology studies [74,75].This suggests that biofeedbackis probably simply a form of behavioural or relaxation therapy. Althoughmanometry and balloon expulsion tests are of limited value in making thediagnosis, they are frequently used to monitor treatment and form the basisof biofeedback.

Recently there have been reports of attempts to produce pharmacologi-cal puborectalis paralysis using botulinin toxin [76], but the results are variable and often temporary. Prospective randomised trials are requiredto determine the efficacy of the technique.

2.1.2.5. Solitary Rectal Ulcer Syndrome

Solitary rectal ulcer is an uncommon condition predominantly affectingyoung adults who complain of tenesmus and recurrent straining. Many alsodigitally aid defaecation. Fiberoptic examination reveals a spectrum ofmacroscopic changes, usually of the anterior rectal wall, that range fromreddening to ulceration. Microscopic examination from the ulcer revealscollagenous replacement of the lamina propria and thickened circularmuscle. Evacuation proctography shows an obvious internal intussuscep-tion in 75%–94% of these patients [77,78]. Over one half of the patientswill also have incoordination of the pelvic floor with evidence of anismus[66]. Recently, it has been shown that there is a close correlation betweenhigh-grade rectal intussusception and a thickened internal anal sphincteron anal endosonography in patients with solitary rectal ulcer syndrome [79].It is unclear whether this thickening is a primary abnormality or secondaryto the mechanical strain of the prolapsing rectum. The aetiology of solitaryrectal intussusception remains uncertain; consequently the management isdifficult. Patients with evidence of anismus should be treated with biofeed-back in the first instance. Rectopexy may be offered to patients with grossintussusception but the results are variable [80], this may also be performedlaparoscopically [81].

2.1.3. Delayed Colonic Transit Study and Abnormal Proctogram

The combination of delayed colonic transit with an abnormal proctogramis fortunately uncommon because these patients are especially difficult toassess. It is necessary to determine whether the delay in transit or the outletobstruction is the predominant cause of the patients symptoms because ithas been shown that outlet obstruction may produce secondary transit


delay [82]. In animal studies the entire gastrointestinal tract was inhibitedwhen a balloon was inflated in the rectum. It is important not to proceeddirectly to colectomy in these patients without first correcting the outletabnormality.Although there are reports of a successful outcome after colec-tomy in the presence of anismus, the results are unpredictable perhapsbecause the anismus was diagnosed by balloon expulsion, which is notori-ously inaccurate. It is the authors’ practice to treat all these patients withbiofeedback. In the event that this is successful then the transit study isrepeated and if delay persists then a colectomy would be considered. Thefew patients who fail to respond to biofeedback and continue to have severesymptoms are offered a diagnostic temporary defunctioning colostomy.

2.1.4. Normal Colonic Transit Study and Normal Proctogram (Functional Bowel Disorder)

A surprisingly large number of patients referred for a surgical opinion haveno objective evidence of constipation on colonic transit studies and havenormal emptying on proctography. These patients should not be offeredsurgery despite the fact that they often complain of severe symptoms andmay be reluctant to accept the objective evidence that gastrointestinaltransit is normal. In the authors’ experience, it is sometimes necessary torepeat the transit study to convince the patient that the transit is withinnormal limits. Patients identified in this way typically have symptoms ofsevere abdominal pain, urgency, and a compelling sensation of incompleteevacuation. Anorectal physiology studies show normal sphincter pressuresbut there is intolerance of intrarectal balloon distension with a hypersensi-tive rectum. In brief, these patients have a functional gastrointestinal disorder [83].

Patients with such symptoms are difficult to treat predominantly becausethere is a poorly understood psychological component to their illness. Anti-depressants have been shown to be moderately effective [84]. In a meta-analysis of 12 randomised controlled trials of the use of antidepressants, ithas been shown that it necessary to treat on average 3.2 patients to obtainsymptomatic improvement in 1 [85]. Psychological treatments includingcognitive and behavioural therapies and hypnosis [86] may also be helpfulbut they are rarely available. Although most trials suggest a positiveoutcome for psychological treatments, they are often methodologicallyflawed and as yet firm conclusions regarding efficacy cannot be made.

There is increasing interest in the complex interaction between the brainand the gastrointestinal tract in patients with irritable bowel syndrome.In experimental studies using positron emission tomography, it has beenshown that cerebral blood flow is increased in response to inflation of a balloon in the rectum [87]. Of more interest however, the site of thisincrease within the brain differs in patients with irritable syndrome whencompared with controls. Whether this difference arises from an abnormal-

ity of the sensory pathways from the gut or a primary abnormality of the brain remains unknown, but it is modified by 5-hydroxytryptaminereceptor antagonists [88,89], which may in the future have therapeuticvalue.

3. Constipation and Megabowel

Megabowel (Figure 13.8) is an uncommon clinical condition that predom-inantly presents as intractable constipation in childhood or adolescence[90,91]. It may involve only the rectum or include the sigmoid and moreproximal colon [92]. Occassionally the condition may be caused by ultra-short–segment Hirchsprung’s disease, although this is unusual in the West,where most cases are identified in infancy. Nevertheless routine work upshould include anorectal physiology studies with measurement of theanorectal inhibitory reflex which is absent in Hirchsprung’s disease. Unfor-tunately, the reflex is also often absent in patients with idiopathic megarec-tum due to the failure of the rectal balloon to stimulate the receptors in the dilated rectum. Consequently, it is the authors’ practice to perform afull-thickness biopsy (myotomy of the anorectal junction) in all patientspresenting for consideration of surgery for megarectum/colon. Althoughmegabowel may also be caused by Chagas disease and chronic intestinalpseudo-obstruction, more than 50% of cases are idiopathic with an intactanorectal inhibitory reflex and evidence of ganglia on full-thickness biopsy.Because the pathophysiology of these idiopathic cases is poorly understood,surgery should only be offered to the most refractory cases and then onlyafter careful consideration.

All cases should be treated conservatively using laxatives and enematafor at least 6 months. Approximately 50% of patients will respond to thisregimen, although the degree of improvement is dependent upon the extentof the disease [93]. Patients with megarectum alone do better than thosewith megacolon. Anorectal physiology studies in isolation have not beenshown to be helpful in either selecting those patients who require surgeryor the type of surgery to be performed Anal-canal resting pressures areinvariably low and the anorectal inhibitory reflex is often absent even whensubsequent histological examination reveals ganglia. In addition, fewpatients with megarectum are able to expel a balloon but known of thesefindings correlates with surgical outcome.

Many surgical procedures have been used to treat megarectum andmegacolon including colectomy and ileorectal/ileosigmoid anastomosis[94,95], proctectomy and coloanal anastomosis [96], pull-through proce-dures, Duhamel operation [97], anal myomectomy, and, more recently,restorative proctectomy. The outcome after these operations is variable,with poor function leading to a high reoperation rates because of continu-ing severe constipation. This array of operations reflects the lack of under-



Figure 13.8. Faecal loading within a megacolon/megarectum.

standing of the pathophysiology of this condition. For example, it isunknown whether the abnormality is limited to the dilated segment ofbowel or extends to involve the nondilated segment. In this respect clinicalexperience has produced contradictory results.While it has been shown thata stoma fashioned above the dilated segment of bowel works well and astoma fashioned from dilated bowel usually fails, it is also recognised that

megacolon may reoccur despite resection of the entire macroscopicallydilated bowel. Despite this caveat, and in the absence of more sophisticatedresearch tests, the author has found the formation of a stoma above thedilated segment to be a most useful way of identifying proximal bowel thathas normal function (Figure 13.9).

There is increasing interest in the use of restorative proctectomy for both patients with megarectum and megacolon. The success rate has beenreported to be as high as 85% although the largest series has only 14patients. Surprisingly, despite the fact that these patients all have low anal-canal pressures prior to surgery, there are no reports of postoperativefailure due to incontinence. This suggests that any sphincter weakness is asecondary rather than a primary abnormality and recovers rapidly.A reviewof surgical outcomes suggests that unlike patients with slow-transit consti-pation and a normal caliber colorectum who respond to colectomy and ile-orectal anastomosis, patients with idiopathic megabowel require at leastremoval of the rectum. An alternative to restorative proctectomy is resec-tion of the dilated bowel with formation of a coloanal anastomosis.Although success rates of 75% have been reported reoperation, for subse-quent dilation of the proximal bowel was required in many patients sug-gesting that the extent of the colonic abnormality is variable. To date thereis no foolproof method for identifying those patients who will respond toproctectomy and coloanal anastomosis and therefore avoid a restorativeproctocolectomy. Colonic physiology studies have been used as a researchtools in an attempt to identify the extent of the colonic motility abnormal-ity, thereby identifying those patients who require restorative proctocolec-tomy but the number of patients studied are too small to draw firmconclusions.

An algorithm is given for those patients who require surgery formegabowel in Figure 13.9. The principal surgical options are restorativeproctocolectmy or proctectomy and coloanal anastomosis. In the absenceof sophisticated research tests, it is the authors’ practice to offer a pouchprocedure to patients with any degree of megacolon. Those patients withonly megarectum are offered proctectomy and coloanal anastomosis if apreliminary defunctioning colostomy above the dilated segment works well.Other groups have advocated the use of vertical reduction rectoplasty andsigmoid colectomy with a resultant improvements in clinical and physio-logical function of patients, but the numbers are small and the work remainsto be fully evaluated [98].


Megabowel

Conservative management for 6 months

Success Failure

Anorectal junction muscle biopsy

Ganglion cells presentGanglion cells absent

Myomectomy

Success Failure Surgery

MegacolonMegarectum

Stoma formation/colonic physiology

Functioning proximallarge bowel

Non-functioningproximal large bowel

Proctectomy and coloanal anastomosis Restorative proctocolectomy

Figure 13.9. Strategy for the management of the megarectum and megacolon.(Suilleabhain CB, Anderson JH, McKee RF, Finlay IG. Strategy for the surgical management of patients with idiopathic megarectum and megacolon. Br J Surg.2001;88:1392–1396. ©British Journal of Surgery Society Ltd. Reproduced with permission.)

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Surgical Management of Constipation

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