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13. Surgical Management of Constipation 271
to have a true intussusception/prolapse. If the patients symptoms correlate
with this finding (i.e., sensation of weight, feeling of prolapse) then they are
offered a resection rectopexy. Examination under anaesthesia is also
performed in those patients who have classical symptoms of prolapse but
in whom an intussusception has not been identified on proctography. This
Figure 13.5. Defaecating proctogram identifying a midrectal intusussecption.
272 I.G. Finlay and A.A. Renwick
excludes or confirms the presence of a midrectal intussusception. Patients
selected in this way have a similar outcome to those who have rectopexy
for overt rectal prolapse, further confirming that the 2 conditions are inter-
related [55]. Those patients who have lesser degrees of intussusception or
only mucosal prolapse are treated by biofeedback.This later group includes
most patients with solitary a rectal ulcer unless there is evidence of a gross
prolapse at EUA.
2.1.2.3. Rectocoele
Rectocoele arises from laxity of the rectovaginal septum. It should be noted
that all female patients have a small physiological rectocoele on proctog-
raphy. Consequently, the rectocoele should have a diameter of at least 5 cm
before it is considered to be of clinical significance. In determining whether
to 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 achieve
evacuation by digitally supporting the posterior vaginal wall. This symptom
has 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]. There
are advocates for each technique. The authors favor a modified transanal
repair first described in 1968 by Sullivan et al. [61].The patient is placed in
the prone position and using an anal speculum a transverse incision is made
in the rectal mucosa. The rectal-wall muscle is then plicated obliterating the
rectocele.Although there are few reports of functional assessment after this
type of surgery, the operation is considered to be successful in over 80% of
cases [62,58]. Ho et al., however, have suggested repair be avoided in those
with weak anal sphincters [63]. There are relatively few complications but
care must be taken to avoid damage to the vagina, which may lead to a rec-
tovaginal fistula. Similar results have been reported using other techniques
including mesh repairs by the perineal route. Prospective randomised trials
are notably lacking. Irrespective of the technique used, infrequent stool
frequency has been shown to lead a poor outcome [59]. There is variable
evidence regarding outcome if the patient also has anismus but this should
not 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-canal
pressure rises during attempted evacuation with closure of the sphincter
mechanism and failure of evacuation. The condition is variously referred to
as obstructed defaecation or pubrectalis paradox. It may be difficult to be
certain of the diagnosis because voluntary contraction of the pelvic floor
with closure of the anorectum is the normal response to avert the call to
stool. 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, anorectal
manometry, electromyography, and balloon expulsion tests are of minimal
diagnostic value due to the high false-positive rate, but these tests may be
useful in monitoring treatment after the diagnosis has been made.The most
reliable method for diagnosing anismus is proctography [66]. Although a
delay in evacuation of 30 seconds is considered to be important [18], in the
authors’ experience proctography also has a high risk of producing false-
positive results, especially in anxious patients who will voluntarily contract
the pelvic floor and sphincter due to embarrassment. Fortunately, in these
patients the true diagnosis can be easily confirmed. Those patients with vol-
untary anismus will empty without difficulty if given the opportunity to do
so in privacy. In comparison, patients with anismus will not empty contrast
material for at least 24 hours and in severe cases for several days (Figure
13.7).
13. Surgical Management of Constipation 273
274 I.G. Finlay and A.A. Renwick
The aetiology of anismus is unknown but it is usually attributed to inap-
propriate contraction of the puborectalis muscle despite the fact that there
is relatively little evidence to support this as the primary abnormality [67].
Further, the mechanism whereby this could occur is unknown although it
has been suggested that it may result from a failure of coordination between
the hindgut and the anorectum [68,69]. Alternatively, it may simply be a
learned 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 controls
subjects [70].
Surgical treatments for anismus (e.g., puborectalis muscle division) have
been abandoned because they are ineffective and have a of risk inconti-
Figure 13.7. Defaecating proctogram that demonstrates anismus or obstructed
defaecation.
13. Surgical Management of Constipation 275
nence. For the past decade it has been widely accepted that biofeedback is
the treatment of choice for anismus [71,72] although the mode of action is
uncertain. It has been suggested that biofeedback may actually modify
higher centre control of defaecation [73]. Several studies have shown that
the patients who gain most benefit are those who have no abnormality of
the anorectum on physiology studies [74,75].This suggests that biofeedback
is probably simply a form of behavioural or relaxation therapy. Although
manometry and balloon expulsion tests are of limited value in making the
diagnosis, they are frequently used to monitor treatment and form the basis
of 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 required
to determine the efficacy of the technique.
2.1.2.5. Solitary Rectal Ulcer Syndrome
Solitary rectal ulcer is an uncommon condition predominantly affecting
young adults who complain of tenesmus and recurrent straining. Many also
digitally aid defaecation. Fiberoptic examination reveals a spectrum of
macroscopic changes, usually of the anterior rectal wall, that range from
reddening to ulceration. Microscopic examination from the ulcer reveals
collagenous replacement of the lamina propria and thickened circular
muscle. Evacuation proctography shows an obvious internal intussuscep-
tion in 75%–94% of these patients [77,78]. Over one half of the patients
will also have incoordination of the pelvic floor with evidence of anismus
[66]. Recently, it has been shown that there is a close correlation between
high-grade rectal intussusception and a thickened internal anal sphincter
on anal endosonography in patients with solitary rectal ulcer syndrome [79].
It is unclear whether this thickening is a primary abnormality or secondary
to the mechanical strain of the prolapsing rectum. The aetiology of solitary
rectal intussusception remains uncertain; consequently the management is
difficult. Patients with evidence of anismus should be treated with biofeed-
back in the first instance. Rectopexy may be offered to patients with gross
intussusception but the results are variable [80], this may also be performed
laparoscopically [81].
2.1.3. Delayed Colonic Transit Study and Abnormal Proctogram
The combination of delayed colonic transit with an abnormal proctogram
is fortunately uncommon because these patients are especially difficult to
assess. It is necessary to determine whether the delay in transit or the outlet
obstruction is the predominant cause of the patients symptoms because it
has been shown that outlet obstruction may produce secondary transit
276 I.G. Finlay and A.A. Renwick
delay [82]. In animal studies the entire gastrointestinal tract was inhibited
when a balloon was inflated in the rectum. It is important not to proceed
directly to colectomy in these patients without first correcting the outlet
abnormality.Although there are reports of a successful outcome after colec-
tomy in the presence of anismus, the results are unpredictable perhaps
because the anismus was diagnosed by balloon expulsion, which is notori-
ously inaccurate. It is the authors’ practice to treat all these patients with
biofeedback. In the event that this is successful then the transit study is
repeated and if delay persists then a colectomy would be considered. The
few patients who fail to respond to biofeedback and continue to have severe
symptoms 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 have
no objective evidence of constipation on colonic transit studies and have
normal emptying on proctography. These patients should not be offered
surgery despite the fact that they often complain of severe symptoms and
may be reluctant to accept the objective evidence that gastrointestinal
transit is normal. In the authors’ experience, it is sometimes necessary to
repeat the transit study to convince the patient that the transit is within
normal limits. Patients identified in this way typically have symptoms of
severe abdominal pain, urgency, and a compelling sensation of incomplete
evacuation. Anorectal physiology studies show normal sphincter pressures
but 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 because
there 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, it
has been shown that it necessary to treat on average 3.2 patients to obtain
symptomatic improvement in 1 [85]. Psychological treatments including
cognitive and behavioural therapies and hypnosis [86] may also be helpful
but they are rarely available. Although most trials suggest a positive
outcome for psychological treatments, they are often methodologically
flawed and as yet firm conclusions regarding efficacy cannot be made.
There is increasing interest in the complex interaction between the brain
and the gastrointestinal tract in patients with irritable bowel syndrome.
In experimental studies using positron emission tomography, it has been
shown that cerebral blood flow is increased in response to inflation of
a balloon in the rectum [87]. Of more interest however, the site of this
increase within the brain differs in patients with irritable syndrome when
compared 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-hydroxytryptamine
receptor antagonists [88,89], which may in the future have therapeutic
value.
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 more
proximal 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 up
should include anorectal physiology studies with measurement of the
anorectal 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 a
full-thickness biopsy (myotomy of the anorectal junction) in all patients
presenting for consideration of surgery for megarectum/colon. Although
megabowel may also be caused by Chagas disease and chronic intestinal
pseudo-obstruction, more than 50% of cases are idiopathic with an intact
anorectal 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 only
after careful consideration.
All cases should be treated conservatively using laxatives and enemata
for at least 6 months. Approximately 50% of patients will respond to this
regimen, although the degree of improvement is dependent upon the extent
of the disease [93]. Patients with megarectum alone do better than those
with megacolon. Anorectal physiology studies in isolation have not been
shown to be helpful in either selecting those patients who require surgery
or the type of surgery to be performed Anal-canal resting pressures are
invariably low and the anorectal inhibitory reflex is often absent even when
subsequent histological examination reveals ganglia. In addition, few
patients with megarectum are able to expel a balloon but known of these
findings correlates with surgical outcome.
Many surgical procedures have been used to treat megarectum and
megacolon 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-
13. Surgical Management of Constipation 277
278 I.G. Finlay and A.A. Renwick
Figure 13.8. Faecal loading within a megacolon/megarectum.
standing of the pathophysiology of this condition. For example, it is
unknown whether the abnormality is limited to the dilated segment of
bowel or extends to involve the nondilated segment. In this respect clinical
experience has produced contradictory results.While it has been shown that
a stoma fashioned above the dilated segment of bowel works well and a
stoma fashioned from dilated bowel usually fails, it is also recognised that
megacolon may reoccur despite resection of the entire macroscopically
dilated bowel. Despite this caveat,and in the absence of more sophisticated
research tests, the author has found the formation of a stoma above the
dilated segment to be a most useful way of identifying proximal bowel that
has 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 been
reported to be as high as 85% although the largest series has only 14
patients. Surprisingly, despite the fact that these patients all have low anal-
canal pressures prior to surgery, there are no reports of postoperative
failure due to incontinence. This suggests that any sphincter weakness is a
secondary rather than a primary abnormality and recovers rapidly.A review
of 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 least
removal 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 there
is no foolproof method for identifying those patients who will respond to
proctectomy and coloanal anastomosis and therefore avoid a restorative
proctocolectomy. Colonic physiology studies have been used as a research
tools 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 firm
conclusions.
An algorithm is given for those patients who require surgery for
megabowel in Figure 13.9. The principal surgical options are restorative
proctocolectmy or proctectomy and coloanal anastomosis. In the absence
of sophisticated research tests, it is the authors’ practice to offer a pouch
procedure to patients with any degree of megacolon. Those patients with
only megarectum are offered proctectomy and coloanal anastomosis if a
preliminary defunctioning colostomy above the dilated segment works well.
Other groups have advocated the use of vertical reduction rectoplasty and
sigmoid colectomy with a resultant improvements in clinical and physio-
logical function of patients,but the numbers are small and the work remains
to be fully evaluated [98].
13. Surgical Management of Constipation 279
Megabowel
Conservative management for 6 months
Success
Failure
Anorectal junction muscle biopsy
Ganglion cells present
Ganglion cells absent
Myomectomy
Success Failure Surgery
MegacolonMegarectum
Stoma formation/colonic physiology
Functioning proximal
large bowel
Non-functioning
proximal 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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