Habitual constipation is a fairly common presentation in the day to day practice of a Pediatrician. There are no universal guidelines regarding the management of constipation. Each physician has his / her own way to deal with the problem. That causes a lot of confusion particularly among the parents, who are anyway, often in the habit of doctor shopping. In this article, I would like to sum up our understanding of this common, yet less understood problem. I shall intentionally leave out discussion on constipation in patients with anorectal malformation, colonic aganglionosis (Hirschsprungs’ disease) and intestinal neuronal dysplasia.
IDIOPATHIC / HABITUAL CONSTIPATION
It is the incapacity / difficulty to pass stool regularly and efficiently. Although many theories have been proposed, we know that the cause is yet unknown. In its most severe form, it is extremely incapacitating and may also cause overflow pseudoincontinence or encopresis. The most serious type of constipation cannot be differentiated from a very serious motility disorder called intestinal pseudo-obstruction that carries a significant mortality rate.
Proposed causes: A number of causes have been proposed to cause idiopathic constipation, but most explanations have no solid scientific basis.
Diet : We talk of constipating and laxative diet. Alteration of dietary habits / conents may help in milder forms but in severe, intractable constipation, diet has minimal role to play. Furthermore, the same diet may cause constipation for some but multiple motions for another (eg. Breast fed neonates).
Psychological basis: Many authorities have tried to explain constipation on the basis of psychological origin1. We believe that constipation can lead to psychological problems, but vice versa particularly in cases of the severe forms of constipation in patients with a giant megacolon, a megabladder, and serious nutritional and developmental disturbances are not self explanatory.
Voluntary stool holding: It is not easy to retain stool voluntarily when an otherwise autonomous rectosigmoid has normal peristalsis. Rather most often a constipated child lands up with a fissure causing enough pain to resent defecation, and hence the psychogenic component is secondary.
Achalasia of internal sphincter: A simplistic explanation is that there is a lack of relaxation of the internal sphincter, known as achalasia2,3. This is a diagnosis based on manometric findings 4. What are the pitfalls of rectal manometry in children? We assess rectoanal inhibitory reflex by dilating a rectal balloon. How can we guarantee that the apparent spasm of the anal canal is not due to sustained contraction of the voluntary sphincter mechanism? We normally do not use muscle relaxants during manometry. Secondly, the size of the rectal balloon remaining the same, in cases of megarectosigmoid, the balloon will hardly be able to generate enough pressure on the rectal wall and theoretically there is a high probability of a false negative result.
Ultra short segment Hirschsprungs’ disease 5,6 – We doubt the existence of this disease entity. Those who believe in this disease entity think that these children have a very short area above the anal canal with absent ganglion cells, which causes dilatation of the rectum all the way to the anal verge. But, normal children have varying areas of aganglionosis proximal to the pectinate line.Intestinal neuronal dysplasia. A study that determines the length of normal aganglionosis in premature infants, newborns, preschool children, adolescents, and adults has not yet been undertaken, and only if ever done, can bring to light the true picture. There is no reason why anorectal myectomy, which involves resection of a longitudinal segment of anorectal wall should cure this ailment.
Newer studies: More recently, we have learned about new potential explanations for colonic hypomotility. A deficiency of substance P immunoreactivity in the colonic nerve fibers of some children with severe constipation has been proposed7. Colonic abnormalities were also found when it was studied with monoclonal antineurofilament antibodies8. Another very interesting finding was an increased plasma level of pancreatic polypeptide and a decreased plasma level of motilin in children with encopresis9.
Anatomical problems – There may be true or aquired stricture of the anal canal ,congenital anal stenosis, improper positioning of the anus vis a vis the sphincter mechanism, and all of these require surgery.
Natural history and clinical manifestations:
The natural history of idiopathic constipation is well documented. The knowledge of natural history has a strong bearing on the management of constipation. Idiopathic constipation is a self perpetuating and self aggravating disease. If inadequately treated and the colon inadequately cleared, larger and larger amounts of stool collects in the colon and this leads to the creation of a megarectosigmoid. We know from basic Physics that pressure inside a tube varies inversely with the diameter of the tube. So formation of megacolon will effectively reduce the intraluminal pressure and cause poor peristalsis and hence fecal impaction which in turn will cause more rectal dilatation. It is this vicious cycle all physicians should constantly remind themselves. One flip side in this story is the mother’s depiction of the ailment. We know of children with fecal retention whose mothers had actually told us that they pass adequate amount of stools.
We believe that in most cases idiopathic constipation is incurable but manageable. So follow-up and treatment have to be long term. In most cases treatments are prescribed on a temporary basis. Then they are tapered or stopped leading to recurrence. The parents get frustrated and indulge in doctor shopping only to face the same cycle again.
When to start treatment ?
Most physicians believe that the symptoms start at the time of toilet training. It is true that symptoms become more evident then. But we believe that the motility disorder is present since birth. Breast fed babies do not show symptoms because of the laxative effect of human breast milk. The moment they are weaned off, they present with constipation. Actually the parents remember most vividly the day when fecal impaction caused some amount of bleeding as the day when constipation first started. So treatment of constipation should begin early.
Anal fissure is another worrisome sign. It is a tear in the anal mucosa caused by passage of hard stool. In turn, it causes painful defecation and makes the patient a stool retainer. Retention of stool in the rectum causes more water absorption and hardens the stool which when passed forcibly causes more aggravation of the fissure. This vicious cycle has to be broken somewhere. Fissure has to be carefully looked for and treated with emollients, local anesthetics, dietary fibres, laxatives and sometimes local steroids and one has to search for the actual cause of constipation.
Fecal impaction is another stressful event which is often overlooked. One should always do a per rectal examination before prescribing laxatives. If laxatives are given in presence of an impacted scybala, abdominal crampy pain gets exacerbated. Vomiting may also occur as the laxative increases colonic peristalsis in the face of a colonic obstruction. In such cases, the child may actually pass liquid stool that passes alongside the impacted stool. We call this spurious diarrhea.
There is another form of constipation where the child actually soils his / her undergarment. This phenomenon is known as encopresis. They behave as fecally incontinent individuals. When the constipation is treated adequately, most of these children again regain bowel control. If the child continues to soil and there are associated urologic symptoms one should assess the spine to rule out occult spina bifida, or a tethered cord or a serious psychological disorder.
Soiling is a socially incapacitating phenomenon. They continue to smell badly and people avoid their company. They are socially outcast and even dread to go to school. The patient is unaware of the smell as he/ she gets accustomed to it. The emotional interrelations in the family gets seriously affected. The child becomes shy, withdrawn, very unsure of himself/ herself.
So by the time a child comes to a surgeon for treatment it is not only a medical problem, but a social problem too. So one has to be careful to listen to the problems, get emotionally involved and bring him / her into confidence, before the treatment proper is started.
DIAGNOSIS
The diagnosis is usually straightforward. One should not think of Hirschsprungs’ disease if the child is healthy and thriving well. Secondly the patients with agangliosis never soil or have encopresis. The kids with idiopathic constipation may have occasional abdominal distension but never have episodes of frank enterocolitis as in H.D. They however have episodes of viral gastroenteritis due to stasis caused by impacted stool but that is never severe enough to cause toxicity, lethargy and death as in enterocolitis.
A contrast enema done with a water soluble dye is the first investigation. The characteristic image of contrast enema in chronically constipated children is that of a megarectosigmoid. The colonic dilatation goes all the way to the anal verge or extends to the level of the levator mechanism, which is recognized because it coincides with the pubococcygeal line. Normally the anal canal and the part of the rectum below the level of the levator mechanism stays collapsed by the effect of the striated muscle tone from the sphincter mechanism. This should not be mistaken as aganglionosis. In Hirschsprungs’ disease, the dilatation of the colon progresses variably from the level of aganglionosis. In habitual constipation only the rectosigmoid is dilated usually, these patients sometimes need localized resection of the rectosigmoid. But the kids with generalized dilatation of the colon belong to the bad prognostic group.
Another entity is a rectoperineal fistula, which may cause incurable constipation in children. This was referred to as “anterior ectopic anus” by some authorities10,11,12. Here, the external anal orifice is abnormally narrow, it is not surrounded by sphincter mechanism in its entire circumference, and does not have a normal pectinate line. We operated on these children and place the orifice in the center of the sphincter mechanism, thereby creating an anus with normal caliber.
Where the diagnosis is still in doubt, we perform rectal biopsy. This is valid particularly in those cases where the child is severely constipated but examination reveals an empty rectum. The child has multiple episodes mimicking enterocolitis but does not soil.
Anorectal manometry is very dubious and has its own limitations.
The entire pathogenesis of idiopathic constipation centers on colonic hypomotility. But unfortunately there are few studies to study colonic motility. Colonic manometry has been tried by placing balloons in different areas of colon recording the waves of contraction13,14. Others have performed recordings of the electrical activity of the colon15,16. It requires the active participation of a Gatroenterologist interested in Pediatric studies to get proper results. A proper colonic motility study can only guide us to the exact extent of hypomotile colon that may need resection to cure the ailment.
Histology of colonic tissue in patients with idiopathic constipation mainly show hypertrophic smooth muscle in the area of dilated colon. One would expect that hypertrophic smooth muscle would cause high power peristaltic waves, but actually the reverse happens. The dilated part of the colon is atonic and aperistaltic.
TREATMENT
Dietary alteration, adequate fluid intake, regular physical exercise, stool softeners, active laxatives form the mainstay of first line treatment.
For the resistant variants, which form the objective of this article, many innovative methods have been tried. Psychotherapy, behaviour modification, biofeedback types of treatment have been tried. These are controversial modes of treatment whatsoever.
Disimpaction : The babies and kids who come to us are often impacted. Disimpaction is a painful but essential pre-requisite for treatment of constipation. We follow the regime of thrice daily enemas to clear the rectum and if it fails, administration of polyethylene glycol alongwith enema is tried. If this also fails, very rarely, disimpaction is done under anesthesia.
Following disimpaction we try medical treatment with gradually increasing doses of laxatives. Doses mentioned in Pharmacology textbooks sometimes are an underestimate for the amount actually required for proper evacuation. We rely on abdominal x-ray films to assess the amount of retained stool. That is the only objective way to assess the degree of fecal impaction.
Many children outgrow their constipation with growing age and changing dietary and activity patterns, but there are a few children with enema dependency. For these children, antegrade enema approach through an umbilical appendicostomy (Malone ACE procedure) can be offered. This gives them independence to evacuate themselves at their convenience.
CONCLUSION
We are yet to know the constellation of factors that cause idiopathic / habitual constipation. We sincerely hope that in the future, more serious scientific approach will be applied to this condition. There is a possibility of histologic abnormalities in this group of patients which we still do not know properly. In future colonic motility studies’ techniques may be perfected to make them more reliable. And, of course genetic engineering will have a role to play in the days to come.
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