Chapter 6 Assessment of the Constipated Patient

Chapter 6

Assessment of the

Constipated Patient

Chapter 6.1

An Overview*

Michelle J. Thornton and David Z. Lubowski

412

Clinical History

Definition of Constipation

Constipation comprises a number of diverse symptoms relating to fre- quency of bowel movement, consistency of stools, and the ease and com- pleteness of defecation (1). The subjective complaint of constipation is influenced by social customs and expectations and has been shown to be neither sensitive nor specific compared with symptom-based criteria. Less than 50% of patients reporting constipation would be given the diagnosis of constipation when colonic transit studies and patient diaries are assessed (2). Symptoms of infrequent defecation—less than three stools per week—

correlate better with gut dysfunction compared with symptoms of straining and incomplete evacuation (2).

The most common definition used in the literature is that of Drossman, described over twenty years ago whereby there are two or fewer stools per week and/or straining at stool more than 25% of the time (3). In 1992, this definition was expanded to include lumpy and /or hard stools more than 25% of the time and the sensation of incomplete evacuation more than 25%

of the time. Patients are considered constipated if they have had two or more of these four symptoms in the preceding three months, while not using laxatives (4). More recently, most comparative studies have utilized the Rome II criteria (Table 6.1-1), although this scoring system has yet to be validated. Knowles et al. have validated an 11 point scoring system—

KESS—that is able to demonstrate the discriminatory ability of multiple symptoms (5,6), but this has not been widely used.

*Editor’s Note: This overview should be read in conjunction with other components

of Chapter 6 as well as the chapters regarding ambulatory manometry, colonic

transit and motility and biofeedback therapy.

Quality of Life Assessment

The general well-being of patients with chronic constipation is lower than that of a comparable normal population, as assessed by quality of life scores.

Constipation severity correlates inversely with the patient’s perceived quality of life. Functional, constipation is associated with an increased reporting of frequent fatigue, severe headaches, and dizziness, which may account for work absenteeism in up to 75% of constipated patients (7).

Interestingly, patients with normal transit constipation have lower quality of life scores than those with slow transit constipation (8), possibly reflect- ing the abdominal pain and bloating that occurs in the irritable bowel syn- drome (IBS Rome II criteria—Table 6.1-1). Mason et al. have recently documented a correlation between pretreatment quality of life scores and a favorable response to biofeedback for constipation (9). Patients who did not experience lifestyle limitations due to emotional problems, pain, or lethargy had a statistically greater response to treatment.

Table 6.1-1. Rome criteria for functional constipation and irritable bowel syndrome.

Rome I Criteria

Constipation = Yes to 2 or more of answers 1,3,5,7 Excluding IBS (see below)

Rome II Criteria

Constipation = Yes to 2 or more of answers 1,3,5,7,10,11 No to answer 4

Excluding IBS

Question: Have you had any of the following symptoms at least one-fourth (1/4) of the time (occasions or days) in the last three months?

1. Fewer than three bowel movements in a week 2. More than three bowel movements a day 3. Hard or lumpy stools

4. Loose, mushy, or watery stools 5. Straining during a bowel movement

6. Having to rush to the toilet to have a bowel movement 7. Feeling of incomplete emptying after a bowel movement 8. Passing mucous (slime) during a bowel movement 9. Abdominal fullness, bloating, or swelling

10. A sensation that the stool cannot be passed (i.e., blocked) when having a bowel movement 11. A need to press on or around your bottom or vagina to try to remove stool to complete

a bowel movement Irritable bowel syndrome (IBS)

Abdominal pain at any site for at least three months in the prior year that was either relieved by defecation often (>25% of time) or was associated with looser or more frequent stool at its onset often; and three or more of:

a) altered stool frequency (<3 stools per week or >3 stools per day often) b) altered stool form (hard or loose/watery stools often)

c) altered stool passage (straining or urgency or a feeling or incomplete evacuation often) d) passage of mucous per rectum

e) visible abdominal distension

Etiology of Chronic Constipation

The symptom of constipation has a broad range of causes (Table 6.1-2). The colon is subject to a number of intrinsic, as well as extrinsic, factors that may affect function.

Dietary fiber deficiency is the most common etiology of mild/moderate constipation. Social factors should always be considered carefully, particu- larly in the elderly. Endocrine causes, particularly hypothyroidism, should

Table 6.1-2. Etiology of constipation.

Dietary Inadequate fiber Social

Immobility

Environmental changes (hospitalization, vacation) Ignoring call to stool

Elderly

Endocrine and Metabolic

Hypothyroidism, pregnancy, hypercalcemia, diabetes, hypokalemia, uremia, hypopituitarism, lead poisoning, porphyria

Central and Peripheral Nervous System Pathology Autonomic neuropathy (diabetes), porphyria, Parkinson’s

disease Drugs

Iron supplements, calcium channel blockers, anticholinergics, antidepressants, narcotic agents, non-steroidal

anti-inflammatory drugs, laxative abuse Psychiatric

Depression, psychoses, anorexia nervosa Gastrointestinal

Structural

Colonic obstruction: neoplasm, diverticular disease, inflammatory bowel disease, volvulus, intussusception Anal outlet obstruction: stenosis, fissure

Functional

Normal transit: constipation-predominant irritable bowel syndrome

Slow transit constipation

• Idiopathic

• Intestinal pseudo-obstruction

• Hirschsprung’s disease

• Megacolon Obstructed defecation

• Hypertonic internal sphincter

• Rectocele

• Pelvic floor weakness

• Anismus

• Idiopathic

not be overlooked. Slow transit constipation is a disorder of colonic motil- ity characterized by a reduction in the frequency, amplitude, and duration of propulsive contractions in the colon. Several pathophysiological differ- ences between normal transit and slow transit colonic function have been identified, which may account for the difference between these conditions.

In slow transit, the colon is hypersensitive to cholinergic stimulation (10), more strongly innervated by non-cholinergic inhibitory nerves (11), and is associated post-prandially with an increased secretion of proximal gut hormones (12). The significance of these findings remains to be determined.

Obstructed defecation may be due to weakness or lack of coordination of the pelvic floor muscles involved in defecation. Paradoxical pelvic floor or sphincter contraction or inadequate relaxation during defecation may cause functional outlet obstruction (13), although the condition has been somewhat over-diagnosed (14,15). In many cases, the precise pathophysiol- ogy may not be clear, and importantly, in some patients, a more generalized colonic motility disorder is present (16).

Prevalence

The prevalence of constipation is dependent upon the definition used.

Population-based studies are limited to subjective patient reporting, and therefore may over-estimate the true prevalence. Between 2% and 34% of Western populations report symptoms of constipation. Applying the Rome criteria, the prevalence of constipation is 4.6% for functional constipation and 4.5% for outlet obstruction (17). A gender association is debated where outlet delay (but not functional) constipation appears to be increased in women (7). Age often has been considered important, although in the age group over 65 years, functional constipation was found in 24.4% and outlet obstruction in 20.5%, which was not statistically increased compared with the general population (18).

Assessment of Constipation

Clinical Examination

A general physical examination is performed to search for evidence of sys-

temic disease associated with constipation. Rectal examination should be

performed to exclude the presence of an anal stricture, anal fissure, ano-

rectal mass, or rectal blood. During rectal examination, perineal descent

with straining can be estimated by palpating the ischial tuberosities. As the

patient bears down, the examiner should perceive relaxation of the exter-

nal anal sphincter (EAS) together with perineal descent. If this does not

occur, obstructed defecation should be suspected.

Stool Diary

Self-reported constipation may be unreliable. When requested to record a stool diary, over 50% of patients who reported severe constipation did not meet the Drossman criteria (2). A stool diary is a simple and inexpensive means of assessing the patient’s symptoms, and is particularly helpful when the symptoms do not match the clinical and radiological findings.

Biochemistry

Requests for laboratory investigations should be based on a clinical index of suspicion. They may include thyroid function tests, serum calcium and creatinine, full blood count, and glucose to help exclude systemic disease.

Psychological Assessment

Psychiatric illnesses such as depression, obsessive–compulsive disorder, and anorexia nervosa are independent risk factors for constipation (19). Several studies also have suggested that underlying emotional trauma may be asso- ciated with constipation and other pelvic floor disorders. A pretreatment psychological assessment may indicate those patients who are likely to benefit from behavioral intervention (20,21) and will assist in the referral of patients prior to surgery.

Flexible Sigmoidoscopy

Flexible sigmoidoscopy and biopsy, where appropriate, may aid in the diag- nosis of the solitary rectal ulcer syndrome (SRUS), a colorectal mass lesion or intussusception. The presence of melanosis coli will help in diagnosing laxative abuse.

Imaging

Barium Enema

Barium enema examination is indicated in patients with longstanding

constipation. The purpose is not to diagnose mucosal pathology, but to

exclude megarectum or megacolon, and a single contrast study without

bowel preparation should be performed because preparation of the colon

or gas insufflation may respectively mask or artificially produce features

of megacolon (Figure 6.1.1). In patients over 40 years of age with recent

onset of constipation or iron deficiency, colonoscopy is the preferred

investigation.

Defecating Proctography

A defecating proctogram provides information about anatomic pelvic floor changes and may be useful in the investigation of obstructed defecation (22). The test may demonstrate poor activation of the levator muscles, retention of barium, or a significant rectocele (significant implies failure to empty the rectocele despite otherwise emptying the rectum). It is impor- tant to recognize that some findings, such as internal intussusception, are secondary and not the cause of the obstructed defecation.

Colonic Transit Studies Radiopaque Markers

This is a test of whole gut transit, which, when prolonged, usually reflects slow colonic transit because time through the colon forms a large compo- nent of whole gut transit time (23). Laxatives are ceased for 48 hours and 20 radiopaque markers are ingested. A single radiograph is taken on Day 5 where 14 markers (80%) will have been passed in normal subjects. Pelvic retention of the markers is consistent with pelvic outlet obstruction, whereas a diffuse scatter is more consistent with colonic inertia. Laxatives and enemas must be avoided for the duration of the study and patient com- pliance must be considered when interpreting the results.

Segmental transit can be calculated by taking daily X-rays for five days and dividing the abdomen into three segments reflecting the right colon,

Figure 6.1.1. Single contrast unprepared barium study showing megacolon.

left colon, and rectum/sigmoid (24). However, if segmental transit is required, usually when selecting patients for colectomy, we prefer to use radioisotope scintigraphy.

Colonic Scintigraphy

Indium-111 diethylenetriamine pentaacetic acid (DTPA) is swallowed and the abdomen is scanned using a wide field-of-view gamma camera at 6, 24, 48, 72, and 96 hours (Figure 6.1.2). The colon is divided into right, left, and rectum/sigmoid sections for analysis. Segmental transport is measured by retention of isotope and total percent retention is calculated. This pro- vides direct evidence of colonic transit, which is increased in slow transit constipation (25,26).

Physiological Studies Anorectal Physiology

Anal manometry will diagnose a hypertonic internal anal sphincter (IAS).

The presence of the rectoanal inhibitory reflex (RAIR) will exclude Hirschsprung’s disease (HD). This is particularly useful with ultra short segment HD, where histology can be difficult to interpret. Manometry is also important to confirm normal sphincter tone when considering a patient for colectomy.

Rectal Balloon Distension Studies. Rectal sensation is impaired in two- thirds of patients with slow transit constipation (22). Loss of sensation may be a useful predictor of outcome of colectomy for constipation.

Pelvic Floor and Sphincter Electromyogram. The normal response to defe- cation straining is reduction of electrical activity in the EAS and puborec- talis and increased activity in the pubococcygeus muscles, which contract and prevent excessive downward movement during defecation (27). In obstructed defecation, there is increased activity of the EAS and puborec- talis during straining (28) due to anismus. These tests should be interpreted with caution because, in many cases, apparent anismus is due to a labora- tory artifact, and testing under physiological conditions shows that anismus is not present in this setting (14,15).

Rectal balloon expulsion has been found to be impaired in patients with anismus (28) and was a popular, simple test of rectal evacuation. Recent careful studies have seriously challenged the validity of this test (29), and we no longer routinely use it.

Upper Gastrointestinal Motility Studies

It generally is accepted that patients with a generalized gastrointestinal dis-

order rather than an isolated disorder of colonic motility have poorer out-

comes following surgery for slow transit constipation. Therefore, patients

with slow transit constipation who have symptoms such as nausea, vomit- ing, and bloating within 30 minutes of eating, weight loss, and upper abdom- inal pain warrant further investigation prior to being considered for surgery (20). Esophageal manometry also may be indicated to exclude a global motility disorder. Gastric emptying studies may be helpful and a barium meal is the best means of excluding megaduodenum. Small bowel transit Figure 6.1.2. Radioisotope colon transit study. (A) Normal subject showing isotope in the right colon 6 hours after ingestion, and passage of isotope through the colon over 48 hours. (B) Patient with severe slow transit constipation showing prolonged retention of isotope. (C) Total percent retention of isotope in the patient with slow transit constipation (shown in the upper line). The upper range of normal values is represented by the lower line (McLean et al.) (26).

A

B

C

studies have not been proven to be a useful predictor of the outcome of colectomy, but failure for all isotopes to enter the cecum within six hours after ingestion raises concern about small bowel dysmotility.

Colonic Manometry

There has been increasing interest in measuring colonic motor activity.

Low-amplitude non-propagating pressure waves are observed, which increase after waking and post-prandially. High-amplitude propagating waves occur with a frequency of 4 per 24 hours and amplitudes of 100 to 200 mmHg. These pressure waves have been studied using a manometry catheter placed colonoscopically (30), and more recently, we have studied the unprepared colon under physiological conditions using a soft 16- channel tube passed transnasally (31,32). Normal defecation is preceded by high-amplitude waves, which may begin in the left colon or more proxi- mally, and it is now clear that defecation is a colonic event that involves more than rectal evacuation alone (33). Some patients with severe obstructed defecation have an absence of propagating colonic waves, and it would seem that rectal symptoms are due to a diffuse colonic motility dis- order in these cases. These tests are evolving and will eventually find a place in the clinical investigation of patients with severe constipation. For further discussion, the reader is referred to Chapter 2.6 on ambulatory manometry and Chapter 2.7 on colonic motility and transit.

Approach to Management

Diet

An empirical trial of fiber supplementation (at least 25 grams of dietary fiber daily) in the form of unprocessed bran or psyllium should be consid- ered at the initial presentation for all patients with functional constipation.

A gradual increase in the dietary fiber content will reduce the side effects of bloating and flatulence. Many patients presenting to specialist Colorec- tal Units will already have been given additional dietary fiber and laxatives, and indeed may seem to have failed all forms of conservative therapy.

However, it is important to be sure that compliance with diet and laxatives has been adequate. Failure to respond to fiber supplementation and initial simple laxative therapy should prompt investigation of pelvic floor function and colonic transit.

Lifestyle and Defecation

Although the place of exercise has not been proven, patients should be

encouraged to take regular physical exercise. They should be asked to avoid

suppressing the urge to defecate and to avoid spending excessive time on

the toilet. Excessive straining may lead to pelvic nerve damage (34) and should be avoided.

Laxatives

A graduated progression from fiber supplements to laxatives should occur.

Lubricants such as mineral oils (liquid paraffin) may be helpful, but may cause lipoid pneumonia and should be avoided in the elderly or patients with severe reflux. Osmotic laxatives are very effective, including Epsom salts (magnesium sulphate), sodium phosphate (Fleet

), or Lactulose, which may be used. Lactulose is a disaccharide that is metabolized in the colon to produce methane and hydrogen gas, and this may exacerbate bloat- ing and flatulence. Stimulant laxatives include anthraquinones (senna, cascara segrada), castor oil, diphenylamines (bisacodyl, sodium picosul- phate), and surface-active agents (docusate) may be considered for differ- ent specific uses and should be considered when other first-line laxatives have failed. There is experimental evidence to show that senna damages the colonic myenteric plexus and we do not use it except where all other com- binations have failed, and generally only in cases where surgery may otherwise become indicated.

Biofeedback

There are no randomized trials confirming the efficacy of conditioning techniques for constipation. The mechanism of biofeedback is also poorly understood, and improvement may be due to the active behavioral inter- vention or a consequence of the attention to and better management of constipation (35). Outcome is also dependent on patient motivation (36).

Nevertheless, there are a large number of nonrandomized trials that show that up to 80% of patients report symptom improvement with treatment (37,38). This symptom improvement correlates with decreased depression and anxiety scores and improved general health (9). The treatment is non- invasive, and we use it routinely in patients whose symptoms and physio- logical investigations suggest an abnormality of outlet obstruction. There is some evidence that biofeedback may improve colonic transit time (39), and some researchers also have advocated its use in patients with diffuse slow transit constipation, although this has not been our practice.

Botulinum Toxin

Botulinum toxin has been used selectively to weaken the EAS and pub-

orectalis muscles in constipation. Initial results suggest that there may be

some role for this treatment (40), but detailed prospective investigation of

its efficacy and safety is required.

Sacral Nerve Stimulation

Although the study numbers are small and follow-up is currently short term, sacral nerve stimulation may prove to have a role in the treatment of intractable idiopathic constipation. The technique probably acts via para- sympathetic nerve stimulation, but other factors, including modulation of rectal sensation, may be important. In one small study, stimulation produced an increased bowel frequency, improved ease of evacuation, and improved abdominal pain and bloating (41).

Surgery

Rectocele Repair

A rectocele is a defect in the rectovaginal fascia, formed as a condensation of the endopelvic fascia. Surgical intervention is recommended on the basis of rectocele size greater than three centimeters (although controversial), barium entrapment during the evacuation phase of defecating proctogra- phy (when the remainder of the rectal contents empties), and the need for manually assisted defecation. A rectocele may be repaired via a transanal, transvaginal, transperineal, or laparoscopic technique. There are numerous studies reporting results, particularly after transanal or transvaginal repair (42,43), but there are currently no published prospective comparative studies. The results of two randomized trials comparing transanal and trans- vaginal repair are awaited. Transanal repair appears to cause less pain than transvaginal repair, but interestingly, dyspareunia occurred with equal frequency in one study (44).

Incontinence associated with rectocele remains an area where more information is required. Recent magnetic resonance imaging (MRI) studies have suggested that although internal or external sphincter defects may contribute to incontinence in patients with a rectocele, there is also often global pelvic floor weakness involving ballooning of the puborectalis muscle and marked depression of the levator plate posteriorly and the levator muscles bilaterally (45).

Internal Sphincterotomy

Martelli et al. first reported strip myectomy for obstructed defecation in

1978 (46). More recent studies with longer-term follow-up have shown that

the procedure has minimal efficacy except for short segment HD (47). Sim-

ilarly, anal dilatation is not effective and is potentially dangerous. In rare

cases, patients with a markedly hypertrophic or hypertonic IAS may require

internal sphincterotomy (48), although recent developments in pharmaco-

logical relaxation of the sphincter with glyceryl trinitrate and botulinum

toxin would obviate the need for surgery in some cases.

Surgery for Slow Transit Constipation Antegrade Colonic Enema (ACE)

Antegrade irrigation of the colon may be used as an alternative to colec- tomy or a stoma in patients with severe laxative-resistant constipation.

Malone modified the procedure described by Mitranoff for antegrade irri- gation of the colon using the appendix in children (49,50), and several studies have shown good results (51). The ACE technique is particularly useful in patients with slow transit or severe obstructed defecation when sphincter weakness is also present, so that the use of laxatives is compli- cated by the resulting incontinence.

Colectomy (See Chapter 6.2)

Subtotal colectomy and ileorectal anastomosis will result in functional improvement in over 90% of patients in terms of frequency of defecation (52,53). Severe diarrhea will occur in up to 10% of cases, which may be asso- ciated with incontinence if the anal sphincter tone is reduced. Incomplete colectomy with ceco-rectal or ileo-sigmoid anastomosis is associated with recurrent constipation in up to 30% of cases. Exclusion of patients with proximal gut involvement is also critical in preventing failure due to recur- rent constipation. Optimal functional outcome might be achieved by seg- mental colectomy after identifying the affected part of the colon, but current motility studies are not sufficiently sensitive to allow this distinc- tion and segmental colectomy has a high rate of recurrent constipation (54).

Although 50% of patients have persistent abdominal pain after colectomy and ileorectal anastomosis, the severity of the pain is usually significantly reduced (53). There are now a number of studies that report an overall patient satisfaction of 80% to 90%.

Conclusions

Functional constipation is a complex physiological interaction of the motor

and sensory function of the colon, rectum, anus, pelvic floor, and higher

centers. It is a symptom rather than a true diagnosis. This overview provides

a broad outline of the assessment and management of patients presenting

with intractable constipation not responsive to the usual remedies,

where the patients’ quality of life is affected and an overview of our unit’s

approach is presented, summarized in the algorithm at the end of this

chapter (Figure 6.1.3). Several important aspects regarding the manage-

ment of these complex patients are dealt with in detail in the chapters that

follow in this section.

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Failure

Anatomical defect

Fibre Laxatives Lifestyle Stool diary Biochemistry

Upper GI motility Ba enema

Psychological assessment Colonic manometry Symptom

control

Constipation

Normal transit Obstructed

defecation

Slow transit

Laxatives ^Laxatives

Surgery Biofeedback Symptom

control

Failure

Segmental colectomy

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+ IRA ACE

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Editorial Commentary

The assessment of patients with chronic severe constipation is highlighted

throughout this book and the use of transit measurement broadly separates

patients into potentially operable and conservative categories. Anal

endosonography and its semiquantitative rôle in the dynamic contractile

function of the puborectalis during straining (the puborectalis displacement

and distance between its inner marking and the internal anal sphincter from

rest to strain) may be a diagnostic aid in anismus. For those patients unre-

sponsive to medical therapy, biofeedback, and toilet retraining, the surgical options revolve around subtotal colectomy and antegrade colonic enema lavage. For the latter procedure some selection of motivated patients is required. Recent data have shown a complex aetiology (and predictability) for postileorectal anastomosis diarrhoea where patients may benefit from preoperative small bowel transit assessment and a systemic assessment of serum PYY tyrosine peptide which can function as a circulating “ileal brake” on ileocaecal transport. Such an assessment may define the benefit in selected cases for the construction of an ileal reservoir and restorative proctectomy in complex cases presenting with combined megacolon and megarectum.

MP