Pathogenesis of functional constipation in children. Review and analysis of the literature.
M.D.Levin; MD, PhD, DSc, Radiologist of Children's Surgical Center, Minsk Belarus(1975-1990);
State Geriatric Center, Netanya, Israel.
Amnon ve-Tamar, 1/2, Netanya, 42202, Israel.
CC – chronic constipation; FC – functional constipation; OFC - obstructive functional constipation; STFC - slow transit functional constipation; IBS - irritable bowel syndrome; EAS – external anal sphincter; IAS – internal anal sphincter; PRM – puborectalis muscle; LAM – levator ani muscle.
Purpose to study pathogenesis of functional constipation (FС).
Material &Method. The 280 patients with megacolon, that was revealed during barium enema, were divided into 3 groups: (1) 95 patients complaining of constipation; (2) 130 children in which the constipation combined with incontinence; (3) 55 children that were hospitalized with recurrent abdominal pain. All patients underwent the dosage hydrostatic barium enema.
Results: The megarectum was identify, as an extension of the rectum over the upper limit of the age norm. Megareсtum always accompanied by the expansion and an elongation of the sigmoid colon. The descending colon was expanded in 70% of cases. The damage of the puborectalis muscle (PRM) were combined with the symptom of the fecal incontinence. In some patients of the third group the non-specific inflammation were determined.
Conclusions: Our data suggest that FC is always caused by functional obstruction of the anal canal as a result of inconsistencies of the fecal width with bandwidth of the anal canal. This leads to expansion of the rectum and increase the capacity of the left half of the colon. The impairment of PRM causes the fecal incontinence. In some children, the chronic intestinal obstruction causes non-specific inflammation of the colon typical for irritable bowel syndrome.
Keywords: Functional constipation; fecal incontinence; irritable bowel syndrome; megarectum; rigidity; barium enema.
Chronic constipation (CC) is a common problem. The prevalence of constipation in the worldwide general population ranged from 0.7% to 79% (median 16%). In children prevalence rate was between 0.7% and 29.6% (median 12%) . Different types of СС are divided into organic and functional. Organic causes include Hirschsprung disease, anorectal malformations and spina bifida. The functional reasons CC include the cases where the cause can be established and made specific correction (hypothyroidism, celiac disease, allergies, elevated levels of calcium and lead) . All other cases of CC covered by the criteria of international groups of experts Rome II, and Rome III are considered functional constipation (FC) [3,4]. The pathophysiological mechanisms of FC remain unclear . Most childhood constipation results from intentional withholding of stool following a painful experience with defecation. . Based on studies in children it is believed that the conscious is not paying attention to the rectal urge and / or suppression of the urge to defecation can lead to fecal retention, with the development of the rectal hyposensitivities, increased compliance and / or megarectum [6,7]. Separately considered cases of chronic constipation accompanied by abdominal pain, which, under the Rome III criteria is the irritable bowel syndrome (IBS) . Among the primary functional disorders are distinguished: (a) obstructive FС (OFC) and (b) FC due to slow transit through the colon (STFC). It is believed that OFC arises due to the violation of defecation (stool evacuation), leading to the expansion of the rectum (megarectum). This is caused by the weakness of the rectal peristalsis, as well as by the insufficient relaxation of the external anal sphincter (EAS) and contraction of the puborectalis muscles (PRM) during defecation, known as dyssynergia defecation. Slow transit is explained by pathology intracolonic nervous plexus . As separate etiological entity the anterior rectocele and inside intussusception of the rectal mucosa are distinguished [9,10]. All these notions about "nosological forms" of FC came in pediatrics from the general gastroenterology. Such a variety of diagnoses due to the use of different research methods: barium enema to determine megarectum ; anal manometry for the diagnosis sphincter dissenergia ; study with radiopaque markers, scintigraphy and wireless capsule to determine the transit speed through the colon , as well as defecography, including computer or MRI defecography to identify anterior rectocele and intussusception mucosa .
The purpose of this investigation was to study pathogenesis of FC in children by analysis of previously published own studies and other scientific data.
This article is a review of the literature, including our previous research, published in Russian in 1983-2015. Analysis of study 280 patients with FC, which were divided into 3 groups is produced. In 1st group included 95 patients aged 1 year - 13 years (mean 5.2 years) with major complaint on chronic constipation. In the 2nd group consisted of 130 children aged 2 to 13 years (mean 7.5 years). They had fecal incontinence, which appeared on the average 2 years after the onset of constipation. In the third group were 55 patients which were hospitalized for recurrent abdominal pain of uncertain location. Age of these children ranged from 2 to 14 years (mean 8.8).
Method. The study was conducted by the dosage hydrostatic barium enema . A barium was introduced into the colon up to the reflux into the terminal ileum. The bottom of the barium bag at the beginning of the study was located 40 cm above the deck of the table. The difference of the barium suspension volumes before and after the colon filling corresponds to the colon volume. The radiopaque restrictor (marker) is strung on the tip of the enema. It is in contact with the anus during the study. After filling of the colon have been made at least two radiographs: AP and lateral. On direct radiograph measured the widths of the different parts of the colon. On a lateral radiograph were measured the maximum width of the vertical portion of the rectum, as well as interval not containing contrast medium between the rectum and a contrast marker on the posterior contour of the tip (Fig. 1).
Figure 1. X-ray imaging of the anal canal in the lateral projection (A) and
scheme to it (B).
А. A child 11 years. The axis of the anal canal (AC) is shifted forward with respect to the axis of the rectum.
B. The scheme: OK - axis of vertical branch of the rectum; NM - axis of horizontal branch of the rectum; AC - axis of anal canal; P - pubis; PRM – puborectalis muscle, P – pubis, R - radiopaque marker near the anus.
This method has been used (1980 - 1983) for the examination of children with chronic and acute abdominal pain, as well as with anemia and localization of the abdominal space-occupying lesions. We selected 65 studies, where history had no information about constipation. These measurements were taken as the norm for different age groups .
Method of the analysis radiographs. The area between the marker (anus) and the rectum, which does not contain a contrast agent is equal to the anal canal length measured by manometry other researchers. Consequently, this is zone of the anal canal contraction.
In order to compare the different studies as well as studies of the same patient at different ages, we calculate the constant (C), which is the integral characteristic of the colon value. It is calculated using the formula:
V× R × к
C = -------------
Where: C – constant, V – colon volume (ml);
R – rectal width (cm);
к – projection distortion factor, which is the ratio of the true width of the marker to its image on the radiograph;
h – patient height (cm).
In norm the constant was in the narrow ranges: 18,5 ± 1.6 at the age of about one year, and 27 ± 0.7 in the age of 11-15 years. Another important characteristic of the norm was the location of the entire sigmoid within the pelvis. Sigmoid colon was always the most narrow part of the colon. The volume of the colon increased with age from 550 ± 124 ml in children aged up to one year, to 1090 ± 42 ml at the age of 11 to 15 years.
Statistical analysis was performed by the method of the Student's t-test. The level of significance was set as P<0.05.
Results: We present in the table only the results of measuring the width of the rectum, sigmoid colon, descending colon and the anal canal length in the patients with FL in comparison with the norm (table). The width of the other parts of a colon in patients with FC does not differ from the norm in all age groups (p> 0.2).
Only in 6 (2.6%) of 225 patients with 1st and 2nd groups with FC all parameters were within normal limits. These were children under the age of 3 years, with disease duration up to six months, which received laxatives. In other cases, the rectum was wider than the maximum limit of the age norm, and in these cases, the sigmoid colon was wider than the norm and elongated. It went beyond the pelvis. The ratio of the rectal width of the FC patients to norm increased with age from 1.16 in to 1.53. The ratio of the sigmoid colon to norm ranges from 1.16 to 1.53. The descending colon has been expanded in 70% of cases. According to the average data, it was significantly wider then the norm, but the ratio to norm was the same at all ages. Expanding of the left colon was always accompanied by an increase in volume of the colon and the increase of the constant (C). All cases of megacolon on 3 degrees were subdivided depending of the constant (C): 1st - (31-45); 2nd - (46-60); 3rd – (> 60).
Compare of the sizes of the anal canal and the left half of the colon at FC with normal indices
N – normal indices; FC – indices in patients with FC; p- value (significance level); FC/N - the ratio of the average parameter of the patients with FC to age norm.
The anal canal length depends on the duration of the disease. Only at an early age, it was significantly longer (p<0.05). Elongation of the anal canal was combined with a typical concavity on the lower contour of the rectum due to hypertrophy and swelling of the PRM (Figure 2, A). As a result of the expansion of the rectum forward, its horizontal branch disappears. At the age older of 3 years, we have seen and a lengthening and shortening of the anal canal. Typically, shortening observed at the megacolon of 3rd or 2nd degree. Sometimes a barium penetrated into the anal canal behind the tip of the enema (Figure 2, B). In other cases it was 2 times shorter than the normal length of the anal canal (Figure 2, C).
Figure 2. Lateral radiographs of the anorectal area in patients with FC. The real diameter of the marker around the anus is 1.6 cm.
A. There is a typical concavity on the lower contour of the rectum due to hypertrophy of the PRM.
B. Shortening of the anal canal as a result of barium penetration into the anal canal behind the tip of the enema.
C. There is drastic shortening of the distance between the barium into the rectum and a marker. The upper part of the anal canal, including the PRM and IAS, are in constantly stretched state, i.e. are not involved in the feces retention.
Addiction the megacolon degree from the age is shown on the graph (Fig. 3).
Figure 3. Schedule. Percent the different degrees of megacolon depending on age.
(1)- megacolon 1st degree - (K = 32 - 45); (2) - megacolon 2nd degree - K = 46 - 60; (3) - megacolon 3rd degree - K> 60.
In some patients with FC during defecography barium flowed a narrow stream because the anal canal was not disclosed (Figure 4).
Figure 4. Frame of the defecography by the child with FC and the scheme to it. Defecation occurs through the narrow anal canal.
In children of the second group the constipation started in 4-7 years and the fecal incontinence occurred through 1-2 years after the onset of constipation.
In the third group were 55 patients which were hospitalized for recurrent abdominal pain the uncertain location. Information about constipation are only in 33 cases. In 4 children constipation combined with encopresis and, in 5 - with episodes of unformed feces with mucus, occasionally streaked with blood. In some patients, the stool had a large diameter, but in most patients the diameter of its was normal, sometimes alternated with sheep feces. The full radiometric analysis was performed in 38 cases of the 55 patients of the 3rd group. In 5 (13%) patients all parameters were within the normal range, in 19 (50%) was found megacolon of 1st degree, in 9 (24%) – 2nd degree, and 5 (13%) - 3rd degree. In 22 cases, the rectal width was within normal limits, including in patients with megacolon. This is because, despite the normal width of the rectum, they had an elongation and extension of the sigmoid colon, and thus the colon volume was also increased. In 87% of patients of group 3 were radiographic signs that indicate a high tone of the rectum and left parts of the colon. Irregular contours of the gut, asymmetric haustration and restructuring of the mucosa relief indicate the probability of the inflammatory process (Fig. 5).
The average age of the patients of 3rd group was higher than that of other groups of patients.
Figure 5. Direct radiographs of patients with a clinical picture of IBS.
А. Megacolon 2nd degree. The elongation and expansion of the sigmoid colon, the narrowing of the descending colon and asymmetric haustration are observed.
B. X-ray picture of non specific inflammation of the left colon. Sigmoid colon is lengthened and widened.
The most recognized pathogenesis of the FC is a vicious cycle that begins with painful defecation and leads to stool-withholding behavior as a result. The vast majority of studies devoted to the factors that lead to painful defecation in early childhood (etiology) that is important in the prevention of the FC . There are fragmentary informations on how the disease develops in cases of untimely treatment or lack of effect from the treatment. The vicious cycle is only the beginning of pathological transformation of the colon, rectum and perineum for many years of the disease. In our study, the rectum was wider of the maximum limits of the age norm in all patients with the disease duration of more than 6 months. With age, the width of the rectum and sigmoid colon are increasing even more, and the width of the descending colon is increased proportionally to age norm. This is evidenced by the relationship of the average indices of patients to age norm.
All our cases of the 1st and 2nd groups correspond to the notion of the obstructive defecation is broadly defined as the inability to evacuate contents from the rectum and is accompanied by symptoms of dyschezia and a subjective sensation of anal blockage during defecation [16,17]. The rectum is stretched as a result of prolonged and repeated delays of stool. Therefore, the volumes of feces (balloon), which in a healthy patient causes the pressure rise to the threshold pressure 3rd order (TP-3) to defecation, in patients with megarectum it causes the pressure rise to TP-2 - inhibitory reaction - relaxation of the BAC and contraction of the EAC and PRM . When the amount of feces in the rectum reaches such a level that the pressure will rise to the TP-3, the diameter of the stool will not match the bandwidth of the anal canal.
Gladman M.A. et al, who examined adults patients, concluded that the maximum limit of normal width of the rectum is 6.3 cm . The width of the rectum increases with age as a result of the increasing the pelvic size and diameter of the stool accumulating in the rectum. This means that the maximum size of the rectum correspond to the maximum size of the stool. It is enough to draw a circle with a diameter of 6.3 cm, to ensure that such a diameter of stool may not be the norm. These authors filled of the rectum with barium of volume to 500 m under minimal pressure. During introduction of 500 ml under minimal pressure, the width of the rectum on the radiograph in patients with megareсtum will more reflect the tone of the rectum, than the true diameter, since a contrast medium is unable to stretch of the rectum to its maximum size, and will be distributed into the left part of the colon. Analysis of these papers indicates that the authors did not take into account the increase in the projection, significance of which depends on the distance from the object being studied (rectum) to the cassette. The greater the patient's pelvis, the more it will increase relative to the norm. At full and large people on the lateral radiograph the rectal size can be 2-fold greater than in reality. Because wrongly set limit of the rectal norm, appeared a false idea of the possibility of chronic constipation with no extension of the rectum, i.e., not obstructive nature. Slow transit of a feces through the colon was detected in them. However, any delay of the feces in left half of the colon, including the obstructive constipation, causes deceleration passage of a bolus throughout the digestive tract. Shafik et al. found that inflating balloon in the rectum leads to increased rectal pressure and causes a significant increase in the tone of the lower esophageal and pyloric sphincters . In response to the inflation of the balloon in the rectum it was also found a significant decrease in pressure jejunum and ileum. The believe that this reaction by the lowering of the small intestine transit allows the rectum to get rid of its content and prevent its excessive expansion . Clinical studies show that in children with FC frequently revealed the gastroesophageal reflux disease as a result of the delay of the gastric emptying . Thus, probably the rectal distension by fecal mass in patients with FC leads to slow passage through the all digestive tract, including the colon, and is not a feature of some part of these patients. Our findings are consistent with studies of other authors, that the slowdown in transit through the colon is secondary to obstructive constipation . The article Ridha Z. et al, dedicated to the differential diagnosis of slow transit constipation (STFC) and functional fecal retention (OFC) which are two forms of severe intractable constipation in childhood diagnosed by nuclear transit studies. The patient selection took place in accordance with the Rome III criteria. These were children who had at least two of the following symptoms: large solid stools; stool frequency of 2 and less per week; encopresis episodes one or more times per week; pain during bowel movements and presence of large stool at the abdominal palpation . Each of these symptoms indicates on the OFC and megarectum. The authors diagnosed STFC if the slowing to 48 hours started out the proximal from rectosigmoid colon. OFС was diagnosed if the delay of colonic transit only in the rectosigmoid department was revealed . This differentiation has no pathophysiological justifications. The difference in moving through the colon depend solely on the degree of megacolon. For example, it was shown that CTFC proceeds with more severe constipation . The more of the stool accumulate in the left part of the colon, the sooner, i.e. more proximally the slow transit begins.
The stagnation of feces and stretching of the colon lumen cause the damage of all layers of its departments. In healthy people during the filling of the rectum or colon by the feces the gut wall are stretched. In this case the thickness of wall is reduced. After emptying the bowel everything returns to its original status due to the high elasticity of the tissues. It was shows how each layer of the colonic wall, including the epithelium, muscularis mucosae, and muscularis propria, changes dramatically in thickness with varying degrees of colonic distension . In FC after some time, in the rectum, as well as in the anal canal wall there are fibrotic changes [22,26]. According to Speakman et all. the fibrotic changes in IAS is a response to a change in muscle tone . There is a correlation between IAS thickening with duration and severity of symptoms, amplitude contraction of the rectum and degree megarectum. Hypertrophy of the IAS and the rectal wall is secondary to chronic pathological stimuli . In chronic colostasis significantly increases the amount of serotonin in the colonic mucosa from the proximal part to the distal part with the maximum in the rectum . When laparoscopic biopsy a deficit of neurotransmitters such as substance P was found . The same changes occur in a normally innervated proximal segment of the colon in Hirschsprung's disease . It follows that these changes are not the cause of disease of the colon, but a consequence of the obstruction at FC. Therefore, there is no reason to allocate the slow transit constipation as an independent form of the FС.
There are three undeniable factor that must be considered when analyzing the pathological physiology of the FC. Firstly, the diameter of the anal canal disclosure in the pelvic floor has certain limitations. Secondly, the rectum forms the stool in accordance with its diameter. And, thirdly, the passing of the formed stool through the anal canal is only possible in the case of conformity of the width of the stool to the maximum possible diameter of the anal canal. Three muscle vectors open the anorectal angle prior to defecation, causing the anorectal luminal diameter to increase to approximately twice its resting size. These vectors are forwards (anterior wall), backwards and downwards (posterior wall). Resistance to passage of a fecal bolus through the anorectum is determined by viscous friction against the anorectal wall and by the energy required to deform the bolus as it flows. The observed changes in anorectal geometry serve to reduce both the viscous friction in the anus and the deformation of the bolus, which reduces the force required to facilitate its passage through the anus. For example, if the effective diameter of the anus is doubled during defecation, the frictional resistance is reduced by a factor of 8 .
Rectal hyposensitivity, rectal hypercompliance, increased rectal capacity, rectal motor dysfunction (phasic contractility and tone), and altered rectoanal reflex activity are all found in constipated patients, particularly in association with 'functional' disorders of defaecation (i.e. pelvic floor dyssynergia) . Rectal compliance depends on collagen content and physical condition of the smooth muscle fibers. Increased compliance or hypotonicity in FC indicates excessive weakness of the wall or the large capacity of the rectum . Thus, in the wall of the stretched rectum there are changes, which weaken of the wall and not allow back to normal state after the rectal emptying, which means a loss of elasticity. The decrease in elasticity of rectal wall at megarectum also in another study was found .
We review the pathogenesis of FL in the development depending on the age and treatment.
The disturbance functions of the pelvic floor muscle
The initial stage. The childhood constipation results from intentional withholding of stool following a painful experience with defecation. It is believed that the conscious is not paying attention to the rectal urge and / or suppression of the urge to defecation can lead to fecal retention. At the next attempt defecation there is a discrepancy between the width of the stool and the bandwidth of the anal canal. Coming feces increases the diameter of stool. Thus a vicious circle arises. In the early disease, the stagnation of feces in the rectum causes the intestine expansion. As a result of constant strain because of dyssynergic defecation, the PRM is hypertrophied and swells. Since the volume of the PRM increased, it tightens anteriorly the upper third of the anal canal and part of the rectum during contraction. This manifest in form of the concavity in the inferior wall of the rectum and the lengthening of the distance from the barium into the rectum up to marker about the anus (see figure 2, A). Treatment of the FC, beginning at this time, may lead to recovery without any consequences.
Further development of the pathological process is characterized by a more pronounced expansion of the rectum. Wide stool, is expelled from the rectum by the strong peristaltic waves, which leads to a stretching and weakening of the PRM loop. Initially, during barium enema a barium penetrates into the anal canal behind the enema tip, as a result of the PRM weakness which is unable to press the back wall of the anal canal to the tip (see figure 2, B). Later, even a slight pressure in the rectum causes a relaxation of the PRM, which manifested by sharp shortening of the distance between the gut and anus (see figure 2, C). Weakness of the PRM leads progressively to fecal incontinence.
Compression and tensile other pelvic floor muscles leads to the failure of the LAM, which during defecation do not disclose the anal canal properly, which increases the frictional resistance and enhances the obstructive syndrome (see figure 4). Megacolon of 3rd degree during defecography may appear as an anterior rectocele or mucosal intussusception.
Dyssynergic defecation is the association of paradoxical anal contraction during attempted defecation. Normally, when a subject bears down or attempts to defecate, there is a rise in rectal pressure, which is synchronized with a relaxation of the PRM and EAS. In patients with obstructive defecation the anal pressure increased or demonstrates an absent or incomplete anal relaxation. It is considered that the etiology of the dyssynergic defecation is unclear. From the point of view of our hypothesis the attempt of defecation at megarectum causes to rise of rectal pressure up to TP-1 but no to TP-2, i.e., causing an inhibitory reaction - relaxation of the IAS and contraction of the PRM and EAS. In order to induce relaxation of the PRM and EAS is necessary to create in the rectum TP-2, which is possible only by increasing the volume of the rectal contents (balloon).
Slow transit constipation. Children with chronic intractable constipation show a similar impaired postprandial colonic response to that seen in adults with slow-transit constipation . We found megarectum in all children with the prolonged FC. The stronger megacolon, the more proximally slow transit is registered. There is no reason to allocate slow transit constipation in a special form of constipation.
Chronic stagnation of feces causes inflammation of the colon. In 19 (50%) of the 38 patients of third group was found megacolon of 1st degree, in 9 (24%) was megacolon 2nd degree, and in 5 (13%) - the 3rd degree. In 22 cases, the width of the rectum was within normal limits, including in patients with megacolon. This is because, despite the normal width of the rectum, they had an elongation and extension of the sigmoid colon, and thus the larger volume the colon. In cases where the width of the rectum was within the normal range, but the extension and elongation of the sigmoid colon were found, suggests that in the past in these patients was megareсtum. Thus, in 33 (87%) patients with chronic abdominal pain the symptoms of obstructive FC in combination with radiological signs of inflammation and an increased tone of the colon have been found. According to the Rome III criteria, such a combination of symptoms (CC and abdominal pain) is characteristic of irritable bowel syndrome (IBS) . Some researchers note that in clinical practice, often there are big doubts about the differentiation of FC and IBS [34,35]. In 1975, E. Smith and C. Gill described the pathogenetic relationship the chronic enterocolitis with intestinal obstruction of different etiologies (Hirschsprung's disease, partial intestinal obstruction). They concluded that chronic distention and stagnation in the small bowel or colon cause the capillary stasis, leading to non-specific inflammation of the mucous membrane up to its ulceration .
Based on the results of examination of patients in third group and analysis of the literature, we assumed that the stagnation of feces cause in some patients with FC the inflammation with increased bowel tone. As a result, in the part of patients the rectal width decreases, which leads to improved patency of stool through the anal canal. The severity of constipation reduced, but as a result of chronic inflammation, the pain threshold reduced on the bowel distension. Perhaps that it is one of the pathogenetic mechanisms of IBS.
Rigidity. Functional constipation in adults there is a continuation of the disease, which began in childhood. Gradually the pelvic floor muscles and the wall of the rectum and colon become damaged. Initially there is hypertrophy of the PRM and LIM, and then they become weak. Their muscle fibers partially are replaced by fibrous tissue. Similar changes occur in the walls of the intestine. As a result, the wall of the rectum loses its elasticity. Gradually, in proportion to the degree of megacolon, there are irreversible processes, when the return of the rectum to its normal width, or close to this size cannot be due to the rigidity of tissue. The scheme of the pathogenesis of functional constipation is presented in Figure 6.
Figure 6. The scheme pathogenesis of the FC.
In recent years, there is a tendency to simplify the indications for use of different contrast agents. Meanwhile, each contrast medium has its indications and contraindications. The barium enema is used not as widespread as before, but it has its testimony in childhood: inflammatory diseases of the colon; diagnosis of the megacolon, including Hirschsprung disease, Chagos diseases, and functional constipation. This is due to the fact that the barium is deposited on the mucosa and makes clearer the transition zone in Hirschsprung disease and improves the visualization of the mucosa in any forms of colon inflammation. Contraindication is the gastro-intestinal perforation. Water-soluble contrast enema is used: after surgery, where possible leakage of the contrast medium into the abdominal cavity; in colostography for visualization of the urethral fistula; in the treatment of the sigmoid colon volvulus.
Our data suggest that the FC is always caused by functional obstruction of the anal canal as a result of inconsistencies of the fecal width with bandwidth of the anal canal. This leads to expansion of the rectum and increase the capacity of the left half of the colon. The impairment of the PRM causes the fecal incontinence. In some children, the chronic intestinal obstruction causes non-specific inflammation of the colon typical for irritable bowel syndrome.
The diagnosis and treatment of children with functional constipation (FC) who fail medical management is an important problem. The goal of treatment to reduce the width of the rectum, in order to the width formed therein stool became correspond bandwidth of the anal canal. Conservative treatment possibly in the presence of the rectal wall elasticity and should be for many months, including both the normalization of the rectal emptying and increasing of its tone. Bisacodyl better to enter into the rectum for stimulate of its tone. The surgical treatment is only justified when the rigidity of the rectal wall appears. Resection of the proximal part of the rectum together with sigmoidectomy [37,38] or sigmoidectomy with appendicostomy  is not physiological, because does not eliminate the reason - the discrepancy of the width of fecal mass, formed in the distal part of the rectum with a bandwidth of the anal canal.
In children with FC who fail medical management, the descending perineum syndrome already exists as a result of the weakness of the pelvic floor muscles (PRM and LAM). As a result of resection of the sigmoid colon the liquid feces come from the descending colon into the broad rectum (Figure 1).
Figure 1. Sigmoid resection (from the article Levitt et al.).
The damaged anal canal is not able to hold them. This explains the fecal incontinence. Over time, the fecal incontinence will change to the chronic constipation, because the rigid and wide rectum will form again a broad stool.
I propose to produce a resection of the posterior wall of the rectum by mechanical seam after the invagination it into the lumen of the rectum (Figure 2).
Figure 2. Scheme of the operation at functional constipation:
A. Megarectum; B. the posterior wall of the rectum invaginated in its lumen; C. instrumental resection of the invaginated portion of the rectum.
This procedure normalizes the width of the rectum and eliminates the rectocele and rectal invagination. It does not eliminate the weakness of the pelvic floor muscles. But the fecal delay in the lengthened and extended sigmoid colon prevents leakage of feces through the anal canal.
Wood RJ1, Yacob D, Levitt MA. Surgical options forthe management of severe functional constipation in children. Curr Opin Pediatr. 2016 Jun;28(3):370-9. doi: 10.1097/MOP.0000000000000345.
De La Torre L1, Cogley K2, Calisto J2, et al. Primary sigmoidectomy and appendicostomy for chronic idiopathic constipation. Pediatr Surg Int. 2016 Aug;32(8):767-72. doi: 10.1007/s00383-016-3913-2. Epub 2016 Jul 2.