Constipation

1.    Definition and Introduction

Image courtesy of MedicalNewsToday Opens in new window Although constipation is most objectively defined as fewer than three spontaneous bowel movements per week, it is a symptom, with a different meaning for different patients.

To one individual the term constipation may imply that the stools are too small, too hard, or too difficult to expel and to others that defecation is difficult, with characteristic symptoms such as prolonged and repeated straining with stool passage more than 25% of the time, rectal fullness, the sense of incomplete evacuation, or the necessity for manual assistance.

Individual’s perceptions of constipation were studied by Moore-Gilson, who found that almost 50% considered constipation purely in terms of frequency of bowel actions, almost 25% in terms of straining, pain, and hard stool, and 30% in terms of both. At present, some use the term constipation exclusively for the description of slow colonic transit, resulting in a stool frequency of fewer than two times per week and reserve the term disturbed or obstructed defecation for all the symptoms associated with impaired evacuation.

Although symptoms such as fruitless straining and incomplete evacuation are rather subjective and unreliable, an international team of experts included these symptoms in its definition of constipation. According to Webster’s English dictionary, constipation is

a term used to describe the subjective complaint of passage of abnormally delayed or dry, hardened feces, often accompanied by straining and/or pain.Webster’s English dictionary

The clinical guidelines of the North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition Opens in new window similarly define constipation as

a delay or difficulty in defecation, present for two or more weeks and sufficient to cause significant distress to the patient.NASPGHAN

Devroed believes that a patient should be considered constipated under any of the following circumstances:

1. if the stool weight is less than 35 g per day;
2. if fewer than three stools for women and five for men are passed per week while following a high residue diet (30 g of dietary fiber);or
3. if more than three days pass without a bowel movement.

Recently, Agachan et al. developed a constipation scoring system based on the following aspects: stool frequency, evacuation difficulties, abdominal pain, time spent in the lavatory per attempt, assistance required for evacuation, number of unsuccessful attempts per 24 hours, and duration of constipation. Because these parameters are unreliable or difficult to evaluate, stool frequency remains as a clinical guide.

Figure X | Physiology of defecation in the anarectal region

2.    Normal Defecation

Stool is normally propelled down the colon to the anorectum, where it is stored until it can be eliminated in a socially acceptable manner. The anorectum stores and eliminates stool through a complex mechanism involving muscles of the pelvic floor, the autonomic and somatic nervous systems, and the group of muscles controlling the anal sphincters.

These interactions have become understood as techniques to study anorectal physiology, such as anorectal manometry, electromyography (EMG), and defecography, have become available.

The internal and external anal sphincters surrounding the anal canal form an angle (the anorectal angle) with the puborectalis muscle (Figure X). This angle is approximately 85 to 105^o at rest.

The bolus of stool is propelled into the anorectum during defecation, where distention of the wall results in a temporary reflex relaxation of the internal anal sphincter, allowing stool to come in contact with sensitive receptors in the anal canal.

The external sphincter simultaneously contracts, giving the individual time to decide if circumstances are appropriate to allow stool to escape. If the individual decides to allow to escape, increased intrarectal pressure from straining moves the fecal material toward the anal canal and the puborectalis muscle relaxes, allowing the pelvic floor to descend. Descent of the pelvic floor straightens the anorectal angle, the external anal sphincter is inhibited, and the fecal material is evacuated. If defecation is to be deferred voluntary contraction of the puborectalis muscle and the external anal sphincter muscle decreases the anorectal angle to less than the usual 85 to 105⁰; defecation is prevented, and the rectum accommodates its contents. In newborn babies and very young infants, the role played by the cerebral cortex in these normal events is not yet developed; therefore, defecation occurs when the internal sphincter relaxes.

3.    Etiology (Causes) of Constipation

Difficulties with defection may result from dysfunction in any portion of the normal mechanism of defecation. Such dysfunction may result from aberrations in anatomy or physiology caused by a multiplicity of factors.

3.1.    Faulty Diet and Habits

Of outstanding importance are the epidemiologic studies of Burkitt, Painter, Walker, and others, which have shown that the fiber content of our foodstuffs is the prime factor that determines the fecal weight or bulk and the rate of transit through the colon.

Inadequate dietary fiber, common in the Western diet, produces sparse, inspisated stools, whereas populations with a high fiber diet may have a normal bowel habit of two or three large, soft motions per day. Because peristaltic movements are stimulated by distention of the intestine, they tend to be sluggish when the food bulk is insufficient to cause a normal amount of distention. Excessive ingestion of foods that harden stools, such as processed cheese, and inadequate fluid intake may be contributing factors. Lack of exercise also decreases colonic activity.

Repeatedly ignoring the call to stool results in insensitivity of the reflex initiated by a fecal mass in the rectum. This in turn results in adaptation of the sensory mechanism so that arrival of further propulsive waves fails to produce an adequate call to stool. Ultimately, all natural periodic urges disappear (Table X).

One of the imagined causes of constipation is the belief that a daily stool is necessary for good health. This belief may lead to the chronic abuse of harsh laxatives. After the bowel has been completely emptied by a purgative, it generally takes two days for fecal material to accumulate in sufficient quantity to stimulate the desire for a bowel action.

Although this may seem self-evident, the absence of a bowel movement often increases the distress of a patient whose attention is focused on his or her bowel function. Further purgation (because of the failure to have a bowel movement the very next day) will unnecessarily abuse the intestine and ultimately lead to a complete loss of natural bowel habits (cathartic colon).

Environmental circumstances such as unfavorable working conditions, travel, and admission to the hospital may cause the patient to ignore the call to stool. Some are obviously only temporary problems.

3.2.    Structural or Functional Disorders

Constipation may be only one of several symptoms with which a patient with disorders of bowel structure will present. Constipation in association with other symptoms will lead the examining physician to the appropriate diagnosis, often with the aid of certain investigative modalities. Clearly, obstructive lesions explain constipation, but patients with these lesions may have alternating constipation and diarrhea.

Similarly, individuals with, painful anal lesions suppress the call to stool because of the fear of the pain of defecation. This suppression only aggravates the problem because the stool becomes harder and more difficult to pass.

Through the use of radiopaque markers, a slow transit rate—particularly along the transverse, descending, and sigmoid colon—can be demonstrated. Its exact cause is unclear. Patients with idiopathic megabowel have a dilated rectum or distal colon, but ganglion cells are present. Transit studies also can show abnormalities.

Patients with irritable bowel syndrome Opens in new window have the dominant complaint of abdominal pain, with constipation only an associated finding. Constipation is not an uncommon symptom associated with diverticular disease and may result from the tendency of the colon to form closed high-pressure segments.

Aganglionosis, whether it occurs congenitally in patients with Hirschsprung’s disease or is acquired because of the neurotoxin of Trypanosoma cruzi, will cause constipation.

In toddlers, conflict arising out of coercive or inappropriately early toilet training is an additional factor that may initiate a pattern of stool retention. In older children, a retentive pattern may be initiated by situations that make stooling inconvenient or uncomfortable, such as a school with unpleasant toilet facilities or group A β-streptococcal anusitis.

Toddlers and older children tend to cross their legs, stand rigidly upright, squat quietly in corners, walk on tiptoes, or hold onto furniture as they wait for the call to stool to pass. The urge to defecate passes as the rectum accommodates to its content. A vicious cycle of retention develops as increasingly larger volumes of stool, desiccated by colonic absorption of the water content, must be expelled, often with increasing difficulty and pain.

Prolonged stretching of the rectal walls, associated with chronic fecal retention, leads to an atonic and desensitized rectum, which perpetuates the situation because large volumes of stool must now be present in the rectum to initiate the call to stool. Some of these patients tolerate rectal distention volumes in excess of 500 mL at anorectal manometry. This functional megacolon, which can be demonstrated on a barium enema, may be confused with the megacolon associated with Hirschsprung disease by the untrained eye.

When large volumes of stool in the rectal vault stretch the rectum, the internal anal sphincter relaxes while the anal canal is shortened, as demonstrated by Loening Baucke and Younoszai. Eventually, the external anal sphincter is no longer able to function adequately when the fecal mass pushes against it. Unformed stool, escaping around the impaction, leaks uncontrollably into the undergarment. This condition is referred as encopresis Opens in new window.

3.3    Neurologic Abnormalities

Defects of innervation such as those that follow pelvic surgery and occur with diseases of the spinal cord and brain are factors contributing to constipation. Severe constipation occurs in all patients who sustain a spinal cord injury.

Menardo et al. demonstrated that patients with injuries between C4 and T12 have a marked prolongation of transit at the level of the left colon and rectum, with minor degrees of transit delay at the level of the right colon. Several surveys have revealed that constipation in patients with spinal cord injury has a significant impact on their quality of life.

3.4    Psychiatric Disorders

Psychiatric disturbances often are associated with constipation. However, the medications used in the treatment of psychiatric illnesses very frequently contribute to or cause constipation in their own right. Some patients may become obsessed with their bowel function or lack thereof and resort to excessive laxative abuse. In addition, certain psychiatric patients will deny bowel actions while, in fact, their bowels are moving. Such patients can be detected with the use of radiopaque markers.

3.5.    Iatrogenic Causes

A host of medications can contribute to constipation (frequent offenders are list in Table X). Bedpans are uncomfortable and should be replaced by bedside commodes whenever feasible.

3.6.    Endocrine and Metabolic Causes

Patients with various endocrine abnormalities with their characteristic clinical patterns may cause constipation. Also included in this group are those patients who are pregnant.

4.    Differential Diagnosis

Constipation is a symptom, not a disease. As such, it may be seen in a heterogeneous group of patients. Although no organic cause is identified in most cases, it is important to be able to identify the many conditions whose symptom complex may include constipation. Table X lists some of these conditions.

The most common condition that must be differentiated from idiopathic constipation is Hirschsprung disease, a colonic motility disorder resulting from segmental colonic aganglionosis, with a prevalence of 1 in 5,000 live births and a male-to-female ratio of 4:1.

It is believed to account for 20 to 25% of all cases of neonatal intestinal obstruction and 3% of constipated children referred to the gastroenterologist. It can lead to severe enterocolitis with fever, diarrhea, and severe prostration, which may be fatal if the diagnosis is not recognized early. Most affected infants develop difficulties with defecation during the first few weeks of life.

Other signs and symptoms associated with the condition include abdominal distention, refusal to feed, and bilous vomiting. In the older infant or child in whom the diagnosis is not made earlier in life, there may be persistent abdominal distention, recurrent fecal impaction, and failure to thrive.

Examination of the rectum in patients with Hirschsprung disease usually reveals an empty vault, although stool is palpable in the abdomen. A gush of air and liquid stool may follow withdrawal of the examining finger. In some patients with short-segment or ultrashort-segment Hirschsprung disease, the diagnosis may be made until later in life.

These patients have long histories of chronic constipation and may have ganglion cells on rectal biopsy, despite anorectal manometric findings consistent with Hirschsprung disease. They are thought to have impaired innervations of some length of the sphincter mechanism. Contrary to the earlier teaching that fecal soiling is not seen with Hirschsprung, these patients may soil, but the soiling is much less severe than one would expect from the degree of rectal impaction.

5.    Investigation

5.1.    History

The diagnosis of constipation must be confirmed first because the patient’s presenting symptoms may be more imagined than real. A simple history will determine the patient’s stool frequency. When a patient has two or fewer bowel actions a week, the diagnosis of constipation is considered. The question is whether the reported stool frequency is reliable enough to diagnose constipation.

Ashraf et a. investigated 45 subjects complaining of infrequent defecation with fewer than two bowel actions weekly. The authors found a striking discrepancy between the reported stool frequencies on the one hand and objective measures on the other hand. More than half the patients who professed constipation were found to have underestimated stool frequency by three or more bowel actions weekly.

In this group, a past history of psychiatric problems was common, and bowel symptoms correlated poorly with colonic transit time. Next, the onset of symptoms is determined because onset in childhood may point to a congenital cause such as Hirschsprung’s disease, whereas a more recent onset might point to one of the specific disorders of bowel structure.

A recent onset in an adult, especially with blood loss and mucus, is more common associated with significant colorectal pathology. Specific questions about dietary and bowel habits, laxative ingestion, other associated symptoms, and prior abdominal or pelvic surgery may lead to the correct diagnosis. Characteristic symptoms may lead to the correct diagnosis. Characteristic symptoms such as prolonged and repeated straining at stool, rectal fullness, sense of incomplete evacuation, and necessity for manual assistance may suggest a defecation disorder.

5.2.    Physical Examination

In most patients with constipation, abdominal findings will be unremarkable. A stool-filled colon may be palpated. Rarely, a mass suggestive of a carcinoma or hepatomegaly suggestive of metastases may be found.

The anal region should be inspected carefully for findings such as fissures Opens in new window, hemorrhoids Opens in new window, fistulas Opens in new window, and abscesses Opens in new window. Digital examination might reveal a mass suggestive of a rectal neoplasm or a rock-hard fecaloma. In female patients with a rectocele, the pocket-like defect of the anterior rectal wall can be demonstrated just above the anal sphincter. Almy has pointed out that the absence of stool in the rectum suggests that the difficult lies above the rectum and makes a disorder of defecation unlikely. This observation is not valid if the patient is using laxatives, enemas, or suppositories.

Anal sensitivity and reflexes should be checked. Deficient sensation may represent a neurogenic disorder and cutaneosphincteric reflexes may be absent. In patients with Hirschsprung’s disease, profuse fecal discharge occurs characteristically after rectal examination.

5.3.    Stool Examination

Gross examination of the stool might reveal a large, hard mass or possibly the pellet-like stools characteristically seen in patients with diverticular disease or irritable bowel syndrome.

Stool also should be examined for occult blood, and any positive findings should be investigated further. It has been suggested that determination of stool weight and examination of stool form are mandatory in the evaluation of constipation, because both aspects are closely correlated with colonic transit time.

5.4.    Biochemical Examination

Routine biochemical examination, including values for electrolytes, calcium, phosphate, urea, creatine, triiodothyronine, and thyroxine, is necessary to exclude those endocrine and metabolic disorders that can cause constipation.

Special biochemical investigations such as of gastrointestinal neuropeptides would be of interest, but they are not readily available. Interest has grown in the effect of these neuropeptides on gastrointestinal motility. Using sensitive and specific radioimmunoassays, the concentration of gastrointestinal neuropeptides can be determined quantitatively.

The effect of these neuropeptides on the motor activity of the upper gastrointestinal tract (stomach, duodenum, and small intestine) has been established, but the exact role of some of these peptides in the regulation of colonic motor activity has not been determined (Table X1).

It has been suggested that gastrin and motilin have a stimulating effect on the peristaltic activity of the colon. Patients with constipation have a smaller rise in circulating blood levels of gastrin and motilin after a meal, whereas reduced motilin levels have been reported in pregnancy, when there is a tendency toward constipation. However, it is still unknown whether or not these phenomena are primary or secondary.

The pharmacokinetics, catabolism, and release of these hormones are very complex. For example, the release of vasoactive intestinal peptide (VIP) from intramural neurons, especially those in the lamina propria and circular muscle of the gut, is induced by stimulation of preganglionic parasympathetic fibers. This finding demonstrates the complex interaction between hormonal and neurogenic factors. Further investigation is necessary to determine the exact role of gastrointestinal hormones, especially in patients with slow-transit constipation.

5.5    Proctosigmoidoscopy

Endoscopic examination is mandatory to rule out the presence of a neoplasm. Nevertheless, in the vast majority of patients complaining of constipation, proctosigmoidoscopic examination will not reveal any abnormality.

Frequently, patients with long-standing laxative abuse, mainly involving laxative ingredients of the anthracene family, will demonstrate melanosis coli, a discoloration of the mucosa that may range from light brown to black. In other patients, a solitary rectal ulcer, sometimes associated with anterior mucosal prolapse, will be found.

5.6.    Barium Enema Examination

Although plain films of the abdomen occasionally show the extent of fecal accumulation, the main diagnostic tool to demonstrate structural abnormalities in the colon is the barium enema or colonoscopy.

In constipation of recent origin, a barium enema study or colonoscopy is mandatory. Sometimes an usually redundant colon is noted; other times an unusually dilated rectum and/or colon is found. The normal range for the width of the rectum and the colon has been established, with the upper limit of the rectosigmoid in a lateral view at the pelvic brim being 6.5 cm.

5.7.    Defecography

In the 1960s, cineradiography was developed for the dynamic investigation of the defecation mechanism. Some of the techniques used in that period were relatively complex, requiring time and sophisticated radiologic equipment. Currently, simplified techniques such as defecography and balloon proctography are available. Studies have shown that these techniques are reliable and simple to perform.

Image courtesy of ResearchGate Opens in new window

Figure X. Defecogram at rest (A), squeezing (B), straining (C) and defecation (D). The anorectal angle (ARA) is measured between the anal canal and the central longitudinal axis of the lower rectum. ARA decreased when squeezing (B), however not enough to reach normal values. Also, a tendency for proctocolic intussusception was observed when defecating (D).

Defecography or evacuaton proctography is an established radiologic technique to image the dynamic changes in rectal anatomy during attempted expulsion of barium paste (Figure X). This method offers the possibility of visualizing abnormalities such as anterior rectal wall prolapse, rectal intussusception, rectocele, and enterocele.

Another application of this technique is the measurement of the anorectal angle. It is generally accepted that this angle, which depends on the tone of the puborectalis muscle, becomes more obtuse during attempted evacuation due to relaxation of the pelvic floor. Failure to increase the anorectal angle on straining, sometimes associated with accentuation of the puborectalis impression, is considered a radiologic sign of anismus.

5.8    Colonic Transit Time

A major step in the evaluation of constipation is the measurement of colonic transit time. The technique can establish an abnormality but also can demonstrate a normal transit time in a patient with a bowel neurosis or in the occasional patient who denies having bowel actions.

With the original method described by Hinton, Lennard-Jones, and Young, 20 radiopaque markers of similar specific gravity to feces were ingested on one occasion on the first day before breakfast. Stools were collected and studied with radiography for 7 days or longer until all the pellets had been observed on a radiograph. A variation of this method has been described by Cummings and Wiggins.

Markers of different shapes were ingested on three consecutive days. Subsequently, all markers present in a single stool collected on the fourth day were counted. This technique reduces the effect of day-to-day variation in transit time by providing three-day transit studies from one radiograph. Although these marker-appearance methods do not provide accurate data on transit through the different colonic regions, they can be used as a simple test to assess whole-gut transit time.

With the Hinton technique, Evans et al. found that 95% of normal male and female subjects pass less than 20% of markers within 12 hours and more than 80% of markers within 120 hours. This finding was similar to the original observation of Hinton et al. in male subjects.

It has been argued that it is more convenient to measure the disappearance of a marker from the colon rather than its appearance in the stool. Therefore, Martelli et al. described a technique whereby the patient ingests a single dose of 20 markers. The progression of the markers is followed by daily films of the abdomen until complete expulsion is noted or for a maximum of seven days after ingestion of the markers.

Normally all the markers have passed within 7 days. The arrival and disappearance of markers in three regions of the colon (right, left, and rectosigmoid) are assessed. For this purpose the spinal processes and two lines from the fifth lumbar vertebra to the pelvic inlet serve as landmarks.

Transit time is considered prolonged when more than 20% of the markers are still present within the colon, 5 days after ingestion. A drawback of interpretation of such studies is that evaluation of transit of contents in any segment is dependent on the amount of markers received from the proximal bowel.

5.9.    Anorectal Manometry

A number of authors advocate the use of anorectal manometry during the initial evaluation of constipation and disturbed defecation to develop individualized and more effective modes of treatment.

In patients with Hirschsprung’s disease, rectal distention does not induce internal sphincter relaxation: hence manometry can be used as a reliable test in the diagnosis of Hirschsprung’s disease. Although manometry is clearly useful in discriminating Hirschsprung’s disease from other forms of constipation, its role in the evaluation and management of non-Hirschsprung’s constipation remains unclear.

There are few data correlating manometric findings with clinical symptoms and outcome of treatment. Studying encopretic children, Loening-Baucke was able to demonstrate that the response to different treatment modalities could be predicted by manometric findings.

Borowitz et al. studied 44 children with chronic constipation Opens in new window and encopresis Opens in new window. Spasm of the external anal sphincter during attempted defecation was correlated with the patient’s age at onset, duration of symptoms, and the frequency of fecal soiling. All other manometric parameters did not correlate; either with the frequency of bowel movements, or with the other reported symptoms.

These observations suggest that manometric findings are not representative of the natural defecation act. They also question the conceptual understanding of childhood constipation, based on the assumption that a diminished sense of rectal distention and paradoxical contraction of the external anal sphincter are the principal causes of constipation and obstructed defecation.

In adults, similar conflicting findings have been observed. Pluta et al. studied 24 female patients with severe and disabling slow-transit constipation who underwent a subtotal colectomy followed by ileorectal anastomosis. No correlation was noted between the results of the operation and the manometric parameters, except in one case.

Patients requiring abnormally high pressures inside a distending rectal balloon for sensory perception and internal anal sphincter relaxation did poorer than the others. Another striking predictive factor, noted by these authors, was a history of psychiatric illness.

Many demonstrate pressure abnormalities can be detected by anorectal manometry in patients with idiopathic constipation. The reflex may be normal, the amplitude of relaxation may be less than in normal controls, or the reflex may be totally absent. The resting pressure of the anal canal may be greater than expected and occasionally is accompanied by a rectoanal inhibitory reflex with an amplitude greater than normal.

5.10    Electromyography

Electromyography (EMG) can be used as a functional test for the investigation of muscle activity and is a proven reliable method for the evaluation of electrical activity in the external anal sphincter and puborectalis muscles.

Through electrophysiologic techniques it has been shown that damage can occur to the nerve supply of the external sphincter and the puborectalis muscle in patients with chronic constipation; this damage is probably due to perineal descent during defecation straining.

Paradoxical contraction of the pelvic floor during attempted evacuation is considered as the principal cause of obstructed defecation. The terms most frequently used to describe this condition are anismus, spastic pelvic floor syndrome, and nonrelaxing puborectalis syndrome. Despite many limitations EMG is probably the most specific test providing the best assessment of pelvic floor activity during straining.

6.    Treatment

6.1.    Diet and Fiber

Acute, simple constipation in infants and toddlers is usually treated first with sorbitol-containing juices, such as prune, pear, and apple juice; addition of pureed fruits and vegetables; formula changes; or medication with high sugar content, such as barley malt extract or corn syrup. Dietary changes can include decreasing excessive milk intake.

Several studies have claimed a causal relationship between cow’s milk exposure and constipation in children, but this could not be confirmed by Simeone et al., Loening-Baucke and Benninga et al.

6.2.    Laxative

If despite dietary changes, the stool is still hard and painful to evacuate, then osmotic laxatives are given, such as polyethylene glycol, lactulose, sorbitol, or milk of magnesia. The key to effective maintenance is ensuring painless defecation until the child is comfortable and acquisition of toilet learning is complete. Behavior modification using rewards for successes in toilet learning is helpful.

6.3.    Biofeedback Treatment

Biofeedback therapy has been used in the last two decades to manage various disorders of defecation in both adults and children.

It is based on operant conditioning, the pavlovian principle of learning through reinforcement, and was first used by Kohlenberg to correct fecal incontinence. Patients are shown a tracing of normal defecation dynamics during biofeedback training. They are then allowed to see their own tracing, and the abnormalities are pointed out to them.

Using the monitor or the physiograph for feedback, these patients are encouraged to correct the abnormalities on their tracings by trying different maneuvers. Sensory retraining is achieved by training the patient to sense progressively smaller volumes of rectal distention using the rectal balloon.

Several studies now suggest that biofeedback therapy is effective in a subpopulation of children with chronic idiopathic constipation and encopresis who are found to have abnormal defecation dynamics on anorectal manometry, at least in the short term. Some recent studies have not found it to be significantly different from conventional therapy in the long term. Biofeedback should be considered in patients failing conventional therapy because a small group of patients with intractable constipation and/or encopresis may benefit from this therapy.

In patients with persistent problems despite adequate treatment, it may be necessary to proceed to further studies, including magnetic resonance imaging of the lumbosacral spine to exclude occult spinal cord abnormalities and colonic manometry to exclude occult myopathy or neuropathy.

6.4.    Surgical Treatment

Surgical procedures ranging from anorectal myectomy to proctocolectomy have been used to treat some adults with intractable constipation. These procedures have a very high complication rate and often have failed to correct the problem.

Obviously, there is no place for proctocolectomy in the management of children with chronic idiopathic constipation, except in a very small number of patients with debilitating symptoms and persistently abnormal colonic manometry in a nondilated colon. Myectomy should be reserved for patients with well-documented absence of relaxation of the internal anal sphincter on rectal distention and a normal rectal biopsy indicating short- or ultrashort-segment Hirschsprung disease (recently also referred to as anal achalasia).

The Malone appendicocecostomy for antegrade colonic enemas (MACE procedure), initially designed for treatment of patients with intractable fecal incontinence, may be used to manage children with intractable constipation. This procedure uses the appendix as a conduit to the cecum. After wrapping the cecum around the base to prevent reflux, the appendix is brought out to the abdominal wall as a stoma through which the colon can be irrigated with tap water or saline in an antegrade fashion. To avoid complications associated with appendicocecostomies, cecostomy buttons can be placed endoscopically for the delivery of antegrade enemas.

7.    Conclusions

Constipation is a very common problem during childhood. In its acute form, it is easily corrected by increasing fluid dietary fiber intake. If not properly treated in the acute stage, a cycle begins when painful defecation leads to deliberate withholding of feces, which may result in an acquired megacolon and, often, overflow incontinence.

Once a withholding pattern has evolved, many patients will do well on a program that includes careful explanation of the pathophysiology of the disorder to all involved, evacuation of any impaction, the use of a laxative in sufficient doses to overcome withholding, a program to regularize the bowel habit, and, above all, close follow-up.

In those not responding to this mode of treatment, an unprepared barium enema and anorectal manometry will identify those needing a rectal biopsy to exclude Hirschsprung disease. Anorectal manometry will also identify a subgroup with abnormal defecatory dynamics who may benefit from biofeedback treatment. Magnetic resonance imaging of the lumbosacral spine and colonic manometry may be necessary to identify occult spine abnormalities and occult myopathy or neuropathy of the gastrointestinal tract.

A role for colonic transit studies has not been well defined in pediatric patients with chronic constipation. It is conceivable that in school-age children and teenagers with chronic constipation in whom a history of withholding is denied, this study will be obtained to differentiate those with slow-transit constipation from those with a functional outlet obstruction so that appropriate therapy can be initiated. Studies are needed to determine what percentage of children with chronic idiopathic constipation suffer with constipation as adults.