Dr. Michael Levin
Research

Figure 5. Direct radiographs of patients with a clinical picture of  IBS.   

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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.

 

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Discussion

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 [15].  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 [18]. 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 [11]. 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 [19].  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 [20]. Clinical studies show that in children with FC frequently revealed the gastroesophageal reflux disease as a result of the delay of the gastric emptying [21]. 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 [22]. 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 [23].   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 [23]. 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  [24]. 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 [25].  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 [27]. 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 [22]. 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 [28]. When laparoscopic biopsy a deficit of neurotransmitters such as substance P was found [29]. The same changes occur in a normally innervated proximal segment of the colon in Hirschsprung's disease [29]. 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 [30].

 

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) [31].  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 [31]. 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 [32].

 

We review the pathogenesis of FL in the development depending on the age and treatment.

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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.

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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 [33].  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) [34]. 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 [36].   

 

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.