Case Based Pediatrics For Medical Students and Residents
Department of Pediatrics, University of Hawaii John A. Burns School of Medicine
Chapter IX.8. Constipation
Ken Nagamori, MD
March 2003

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Case #1: At her one month well child visit, worried parents ask about their child's protuberant abdomen. She had been breast-feeding well during the first week, but her intake has been declining and she has begun spitting up. Physical examination finds lethargy, pallor with diaphoresis, tachycardia, distended loops of bowel, and rectal examination finds a narrow anus, and further insertion gives the impression of putting on a glove two sizes too small. The narrow canal extends for two centimeters, then widens into a pool of loose stool. When the examining digit is withdrawn, it is followed by a sudden spurt of particularly foul-smelling stool laden with mucus and streaked with blood, accompanied by a moderate amount of flatus. Questioning the parents identifies the failure to pass stool or flatus without stimulation with a rectal thermometer, having received instruction to do so from her aunt who is a nurse.

An abdominal series is obtained which demonstrates dilated bowel loops and a pattern resembling an acute bowel obstruction. Hirschsprung's disease with acute enterocolitis is suspected.

Constipation is a commonly used term, but its definition is somewhat ambiguous. It could refer to conditions such as: a) the stools are hard, b) the stool is difficult or painful to pass, 3) no stools for a period of time, 4) a bloated feeling, 5) painful cramps associated with a segment of stool that is not moving well, 6) a chronic condition in which a patient's stooling frequency is less than average. All of these definitions are used in medical and/or everyday communication, but it is preferable to use specific terms to describe the symptoms of the patient. The specific findings and their clinical significance will be described in this chapter.

Enterocolitis (as seen in case #1) is the extreme sequel of fecal retention, and is almost unique to Hirschsprung's disease, itself a uniquely pediatric version of the broader definition of chronic constipation: "a delay or difficulty in defecation, present for two or more weeks, sufficient to cause significant distress to the patient" adopted by the guidelines of the North American Society for Pediatric Gastroenterology and Nutrition (NASPGN) (1). The subject is best broken into two broad categories: infants and children.

Infantile constipation: Per the guidelines, this does not include neonatal delays in defecation since the structural anomalies (imperforate anus, cloacal exstrophy, and other perineal anomalies, as well as intestinal atresia, stricture or web, volvulus, duplication, or perforation) and genetic diseases (e.g., meconium ileus of cystic fibrosis) often present in the first few days. Newborns should pass their first meconium stool within 24 hours. Those who don't have a higher risk of GI conditions associated with constipation. However, this criterion should not be relied on in isolation since pathologic conditions will not necessarily present this way. The algorithm proposed by the NASPGN constipation subcommittee emphasizes early suspicion of serious disease, by rapidly sorting out newborns with delayed passage of meconium for rectal biopsy and directing infants with "fever, vomiting, bloody diarrhea, failure to thrive, anal stenosis, tight empty rectum, impaction and distention" (1) to immediate further evaluation, including subspecialty consultation as needed.

The workup begins with a thorough history and physical examination. The above alarm indicators are searched for, as are signs of other structural anomalies. The rectal examination is key, with careful assessment of the anal location, anal neurologic function (the anal wink, which assesses both the sensory afferent and motor efferent pathways), anal structure (looking for distention of the internal anal sphincter), anal tone (looking for spasticity or patulousness), function of the muscles of the pelvic floor (which provide additional help with control of defecation), and rectal diameter and tone (looking for signs of chronic distention even if no stool is present on the day of exam). The anal location should be halfway between the posterior border of the scrotum or posterior fourchette and the tip of the coccyx. Anything outside of the middle third of this region should raise the suspicion for a "perforate imperforate anus" (a structure resembling an anus is visible externally, but it is not contiguous with the rectum). If benign constipation is found, treatment is stratified based on age and developmental state.

Exclusively breast fed infants are permitted a longer interval between stools if they show no signs of distress or distention and if they are not prone to becoming impacted.

In exclusively formula-fed infants, my favorite strategy is the substitution of a commercially available partially hydrolyzed formula, which may produce suitable loosening of the stools. Malt soup extract (a dehydrated powder derived from an effusion of malted barley used in the brewing industry) has been advocated by the committee, as have corn syrup, lactulose or sorbitol, while the use of mineral oil was cautioned against due to the risk of aspiration posed by the frequency of gastroesophageal reflux and swallowing incoordination in this age group.

Impaction is most commonly dislodged by glycerin (non-stimulant) suppositories for which the commercially pre-softened versions sold in soft plastic applicators (glycerin gel) have been my personal favorite, as they provide more immediate relief (the traditional refrigerated suppositories require a wait while they melt in situ). Stimulant enemas are to be avoided in young infants.

Older infants who are of an age where pureed foods would be appropriate should have the fiber content of their diet optimized (i.e., push fruits and vegetables and reduce the other starches). Another personal favorite in the older formula fed infant is the use of undiluted apple juice (not apple drink) for its sorbitol content, titrating the amount administered to the stool texture while making certain that formula intake remains adequate. Pear and prune juice can also be used as they are high in sorbitol, but the cost of the former and the TASTE of the latter are often limiting factors.

Case #2: This 6 year old male presents with fecal soiling on a daily basis, which began in late October. He claims he "can't tell when" he is about to soil. His parents report multiple bouts daily of fecal urgency where he rushes to the toilet, only to pass small amounts of diarrheal stool. His toilet sitting behavior is peculiar in that he sits far back on the toilet seat with his knees extended and his toes pointed, straining at defecation. Once or twice weekly he will pass a very large caliber formed stool, which has on occasion plugged the plumbing. This pattern was not thought to be a problem by his parents as it began shortly after they began potty training him at two years old so that he could enter preschool earlier than rest of the neighborhood children. The dietary history finds that he eats the school breakfast and lunch, and will often not touch his vegetables at supper. Closer questioning indicates he does not pick fruit or vegetables from the salad bar at school, and the school typically offers only sweet buns or a burrito for breakfast. Physical examination finds a midline mass in the lower abdomen, with a rectal examination that shows a normally placed anus with an intact anal wink and a perineum coated with stool. The anus is shortened with the internal anal sphincter dilated by a massive boule (little football) of formed stool. You are unable to accurately assess the diameter of the rectum as the stool appears to fill the pelvic bowl. The stool tests negative for occult blood.

Unlike the child with Hirschsprung's disease in the first illustration, the retention of stool in the older child who does not have a structural or neurogenic anomaly (as seen in case #2) will NOT cause secondary inflammation and enterocolitis, regardless of the duration of the problem. This lack of inflammation is an important differentiating factor that permits immediate identification of the older child with chronic constipation. The primary cause is voluntary fecal withholding, usually due to fear of pain on defecation, giving rise to the term "Psychogenic Constipation". The often accompanying overflow diarrhea or involuntary soiling arising from passage of looser chyme above and around the impaction is termed Encopresis in verbal analogy to enuresis. In simpler terms, the child has a football shaped mass of hard stool in the rectum which reduces the sphincter's ability to hold in liquified stool (chyme) coming from above, which results in soiling. The withholding behavior most often arises from a pattern of passage of large caliber stool as was the case with our illustration, but it can arise in response to a single traumatic event, such as a particularly large stool resulting in a traumatic fissure, a too-rapid transition from diarrhea with a raw perineum to fully formed stools, perianal cellulitis (more properly erysipelas, an intensely painful superficial infection of the anus and surrounding structures with Group A streptococcus identifiable by culture of the affected area), or least frequently but most insidious: overt trauma of physical or sexual abuse.

As in infantile constipation, the history and physical exam are key. The above historical markers are useful in establishing an understanding of the process by the patient and his or her caregivers. Dietary issues must also be explored, as well as the pattern of toileting (it is amazing how little time and opportunity school age children seem to have for sitting on the toilet, with some schools having policies of allowing only two minutes per bathroom break).

The issues on the physical examination of the older child are the same as those of the infant, particularly those regarding the rectal examination. Indicators of failure to thrive are more important beyond the first year, since celiac disease and cystic fibrosis occasionally present with constipation instead of diarrhea, and Crohn's disease can leave the rectum fully capable of extracting fluid from the reduced flow of chyme arising from the reduced appetite, if the inflammation is confined to the small bowel or proximal colon. Hypothyroidism is a particularly rare (but often cited) cause of constipation. A particular caution regarding Hirschsprung's disease bears noting as a significant fraction of the cases present beyond the second year of life in children who require stimulation to trigger defecation: repeated suppositories and enemas will often dilate the spastic segment making it impossible by digital examination alone to identify what should otherwise have been a microcolon. If suspicion is high (inability to spontaneously pass flatus or a strict requirement of stimulation to pass stool which when triggered tends to be foul, loose, and voluminous), an unprepped barium radiographic colon examination is indicated. This study should specifically look for a transition zone, to and fro peristalsis in the unobstructed segments, or uniform mixing of the contrast material throughout the colon (rather than concentration of the remaining barium in the rectum) on the 24 hour delayed film (hence the stipulation for barium rather than water soluble contrast which would tend to be absorbed by the next morning). If the radiographic study is equivocal, anorectal manometry may be of benefit. If either are indicative of Hirschsprung's disease, the diagnosis is confirmed by biopsy of the rectum deep enough to include the myenteric plexuses, as their absence indicates the disease.

If simple constipation without impaction or soiling is identified, therapy begins with education regarding the need for a more regular defecation pattern to prevent progression of the problem.

Dietary intervention is advocated, emphasizing fiber and fluid in accordance with proper nutritional guidelines. Here I find a concrete set of recommendations is most helpful in facilitating compliance, and I have abridged the USDA's food pyramid (2) to a set goal of 6 servings of fruit or vegetables daily with a like number of servings of fluid, which is even further simplifiable to 2 servings of fruit or veggies at each meal which is easily understood by preschool AND adolescent patients.

More importantly, the need for regular toileting in the already potty-trained is emphasized, and I ask that they sit on the commode twice daily after meals to take advantage of the gastrocolic reflex to promote more regular rectal emptying. As in our illustration above, there must be an immediately preceding meal for the process to be most effective, and I have found that eating two fruits before toileting to be helpful. Suppers eaten out should be followed by a trip to the restaurant toilet to avoid missing the increased post-prandial peristaltic activity. A five minute time limit is set for commode sitting to avoid any sense of a punitive nature to the requirement and in some cases I will advocate using a kitchen timer in a "beat the clock" game if appropriate for the patient's personality.

Encopresis on the other hand is an indicator of repeated impaction, and usually is accompanied by enough dilatation as to render the rectal musculature patulous. Here again, education is key, and to simplify the biophysics (the wall tension is proportional to the fourth power function of the bowel lumen diameter), a quick analogy to a balloon that has been repeatedly inflated to the point of flaccidity is readily within the experience of most 4 or 5 year olds. Likewise an analogy to repeatedly compacting the trash over a 3-4 day period rather than dumping it daily will usually trap a kindergartner into admitting such behavior is likely to lead to a heavier, harder and bigger trash bag (and stool). Most importantly, education and discussion is important which should center on the cycle of pain at defecation leading to withholding which results in larger, firmer stools which in turn leads to more pain at defecation, perpetuating the cycle. This helps create understanding in the patient and the parent as to the origin of the process and its ultimate eradication. A thorough discussion of the mechanics of impaction and overflow passage of the as-yet unformed stool around the obstruction helps explain why distention of the rectum and internal anal sphincter and distortion of the levator structures of the pelvic floor result in inadvertent passage of loose stool whenever voluntary control of the external anal sphincter is relaxed. A thorough understanding is important in defusing the animosity that often arises between the patient and caregivers (parents, school, babysitters, etc.) over misunderstanding of what causes and perpetuates the soiling.

Treatment in the impacted, encopretic patient starts with disimpaction. High dose mineral oil and polyethylene glycol bowel preparation solutions have demonstrated efficacy and magnesium citrate, lactulose, sorbitol, senna and bisacodyl having been used anecdotally (1). Though the NASPGN subcommittee found that the oral route can be effective, typically this route is messy and more time-consuming. I strongly prefer a series of hypertonic phosphate soda enemas that are administered at 12 hour intervals (3). Typically only 3 are required, but the importance of removal of all formed elements is emphasized to prevent worsening the overflow diarrhea in the face of the fecal softening to follow. Caution is advised in using too much or too many enemas as each leaches a substantial bolus of calcium. In the case of particularly large and firm impaction, pre-softening by application of a mineral oil enema an interval before the stimulant one can be helpful. Saline enemas were also advocated by the committee as safe and effective, but soap suds, tap water and magnesium enemas are discouraged due to toxicity (1).

The next step is fecal softening, the issues being two-fold: produce a stool loose enough to be eliminated by the patulous rectum, AND eliminating any association of pain with defecation. Again, while the committee found lactulose, sorbitol, magnesium hydroxide, magnesium citrate, and mineral oil to be effective (1), I strongly prefer mineral oil (3) starting at 2-3 ml/kg/day but specifically titrating the dose to achieve the desired stool texture which I specify as "pancake batter", which has enough form to be routinely retained by the internal anal sphincter yet which is loose enough to empty out of the rectum with little more force than that of gravity alone whenever the levator structures of the pelvic floor are lowered and the anal sphincters are opened. In most cases, a patient whose rectum is dilated enough to allow soiling will have trouble expelling stool even the texture of toothpaste, which is the softest that can routinely be expected from fiber and fluid alone. A looser stool is needed to start the process, and mineral oil provides the cheapest and least flatulent method of attaining that goal. While the committee also made provisions for short-term addition of laxatives to this regimen (1), I feel anyone whose rectum is patulous enough to require such additional assistance, should have subspecialist evaluation, as this is by far the exception rather than the rule.

The third step is effective toileting: the already potty-trained patient should be seated on the commode with good foot support (to obviate any tendency to use the musculature of the buttocks and legs to assist in further withholding activity) on the commode twice daily after meals under the same guidelines and for the same reasons as outlined in the simple constipation as above. The sitting is made "non-negotiable" simply to ensure its application as it will become the most enduring and important part of the regimen as the weaning process progresses. Those who are not yet potty-trained are excused from formal sitting but are encouraged to crouch in diapers after meals in an analogous fashion.

Once a better than daily bowel habit is established and withholding is clearly extinguished, weaning off the mineral oil can begin. It is taken VERY slowly, in part to avoid recurrence of pain and resumption of withholding, but more to allow time for the patulous rectum to regain motor tone. I illustrate the importance of this to the patient and family by referring back to the balloon illustration, pointing out the difference between inanimate latex and living muscle, which can regain tone and function. I specifically warn that the process will take months to improve, and that prolonged use of mineral oil has been proven benign (4). This helps improve adherence to the long-term nature of the measures involved, and weaning typically occurs at monthly intervals, and then ONLY if the rectum is indeed shrinking in diameter (and improving in function) and if the withholding remains extinguished. Failure with either issue should result in either maintenance at the current step or return to the next higher one.

Adherence to the mechanical measures involved typically results in an immediate return to continence with the completion of disimpaction, as the nondistended internal anal sphincter is able to retain the loose stool. Continued adherence to the slow weaning typically results in return to long term function (and confidence) through the months of steady increase in stool texture. Permanent adherence to a daily defecation pattern results in long-term avoidance of reimpaction, and is the ultimate goal of the process. Each step along the way involves the physician acting as coach, cajoling and encouraging patients and caregivers, solving problems in techniques, and refereeing any residual conflicts. It must be kept in mind that control in this issue lies with the patient. There is nothing we can (or should) do that will force regular toileting, and there are times when I have to call a "time out" from the process to enable the patient to proceed on his or her merry way until THEY are ready to work on the problem. I often remind parents that the only thing one will die of with routine encopresis is embarrassment, remembering that children are often beaten to death by caregivers for soiling behavior. As can be seen above, the initial visit to address the issue of encopresis can be particularly time-consuming, not with regard to the history or physical examination, but because of the need to impart the understanding of the process of the disease that will encourage an apprehensive child to undertake the measures needed to clear it. The hour rapidly fills with illustrations and instruction, and does not readily fit into a routine sick-child office visit. Time must be set aside for proper handling of the process, and I know most consultations for encopresis arise from the inability to carve out such time in the primary care practice setting.


1. The nurse points out a two day old healthy term infant who is otherwise ready for discharge who still has not passed meconium. Your next step is:
. . . . . a. Order a suppository prior to discharge.
. . . . . b. Careful physical examination, including digital rectal examination.
. . . . . c. Give a normal saline enema to prep for a barium enema.
. . . . . d. Call radiologist to discuss an unprepped barium enema
. . . . . e. Rectal biopsy.

2. The exam of a 3 year old with recurrent impaction is normal except for the impaction and the absence of an anal wink. Which of the following are true.
. . . . . a. An anal wink is not commonly found in this age group.
. . . . . b. The anus may be so traumatized by the impaction that the wink cannot be reliably elicited.
. . . . . c. There may be a neurogenic component to the problem in addition to the psychogenic one.

3. Your examination of a chronically soiling 13 year old female finds a normal sized rectum containing soft stool. Is this routine encopresis?

4. A 6 month old infant has been getting suppositories and enemas every 3-4 days because she does not otherwise defecate. The stools were passed without apparent trouble on breast feeding. Rectal examination finds a normal sized rectum as far as you can reach. Does this rule out Hirschsprung's disease?

5. The barium enema performed yesterday was read as normal, but the remaining barium did not pass overnight. You obtain a followup film this morning, and find dilute barium evenly distributed from the cecum to the rectum. What is the likely diagnosis and why?


1. Baker SS, Liptak GS, Colletti RB, et al. Constipation in infants and children: Evaluation and treatment. J Pediatr Gastroenterol Nutr 1999;29:612-616, downloadable from


3. Fitzgerald JF. Encopresis. In: Green M, Haggerty RJ. Ambulatory Pediatrics II. 1990, Philadelphia, WB Saunders, pp. 121-123.

4. Clark JH, Russell GJ, Fitzgerald JF, Nagamori KE. Serum beta-carotene, retinol, and alpha-tocopherol levels during mineral oil therapy for constipation. Am J Dis Child 1987;141:1210-1212.

Answers to questions

1. Answer d is correct, and the radiologist will appreciate the warning as to why the exam is being requested without prior bowel cleanout (which may otherwise be performed as part of the radiology routine, rendering the same end result as answer c). Answer a will not only miss the diagnosis but may also render diagnosis more difficult later if the pattern is set for stimulation for defecation. Answer b may give the diagnosis if a microcolon can be identified on exam, but can make interpretation of a barium enema difficult. Answer c is wrong for the same reasons as a and b. Answer e is doing too much too soon.

2. Correct answers are both b and c. Anal winks can be expected at any age unless the anus has indeed been badly traumatized. Its absence usually indicates a neurogenic component, and the examiner is prompted to carefully assess the tone of the sphincter and retrospectively look for other signs of aberrant function of the longer neuron sensory and motor tracts or signs of sacral anomalies. If the issue is still in doubt, it can be deferred by one visit. The process can still be addressed by full fecal softening and re-establishment of regular bowel habits since the therapies diverge at a later stage where a timing suppository needs to be added to maintain regular defecation as the weaning progresses and the stool becomes firmer. Full fecal softening is needed initially for both causes to address the flaccidity of the rectum.

3. No, the absence of impaction is worrisome, and the behavioral and social history are likely incomplete. The above pattern suggests voluntary soiling, in which a socially uncomfortable behavior is expressed to avoid an even more uncomfortable behavior, such as sexual abuse.

4. NO! The enemas may have dilated the rectum beyond the reach of the examining digit, and it is common for patients with short segment Hirschsprung's disease to pass the softer stools of breast feeding but have trouble with formula and pureed food. Expert radiographic evaluation is necessary, and the assistance of a pediatric surgeon or gastroenterologist may be helpful.

5. This is the typical appearance of the delayed view in a patient with Hirschsprung's disease. The obstruction is of high enough a grade that the portion of the colon with normal ganglion innervation has set up a "to and fro" pattern of peristalsis, evenly mixing the remaining barium with the increased fluids present in the lumen, rather than transporting the barium to the rectum where the excess fluid is removed (which is the appearance of the normal colon).

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